HSEHealth & Safety

Executive

Feasibility study into the establishment of a retrospective cohort study of workers in the

British semiconductor industry

Prepared by the Institute of Occupational Medicine and London School of Hygiene and Tropical Medicine

for the Health and Safety Executive 2005

RESEARCH REPORT 384

HSEHealth & Safety

Executive

Feasibility study into the establishment of a retrospective cohort study of workers in the

British semiconductor industry

H A Cowie, K Creely, B G Miller Institute of Occupational Medicine

Research Park North Riccarton

Edinburgh EH14 4AP

M Ahern, A Fletcher, B Armstrong London School of Hygiene and Tropical Medicine

Keppel St London WC1E 7HT

The HSE has studied cancer risks in workers from one semiconductor manufacturing plant in Greenock but, because of the small numbers in the study, the results are difficult to interpret. There is therefore an interest in the feasibility of studying a larger cohort, from across the UK semiconductor industry. The power of such a study would be related to both the numbers of workers and the length of their employment in the industry.

This study set out to visit plants and inspect the records held, in order to investigate: whether sufficient data are held to allow the identification of a historical cohort; whether good descriptions of past jobs and working conditions are available; whether other important data such as smoking habits are held; and whether, taking these factors into account, a study would be feasible and sufficiently powerful.

An epidemiologist and an occupational hygienist visited each of eight plants selected because they had the largest workforces and were longest established. Using standard pro-formas, information was collected about the nature and extent of employment and other records held for individuals. Knowledgeable staff were interviewed about the history of the plant, hygiene monitoring practices and use of chemicals. Detailed reports were agreed with the companies. Similar information was sought by questionnaire from smaller companies, or for plants now closed.

We found that, given suitable clearance to access the company records, it would be feasible to amass a cohort of at least 12,000 current and ex-workers. This would allow comparison of mortality or cancer incidence both with external reference rates and between workers involved or not involved directly in wafer fabrication. Data on smoking habits are available for only part of the cohort, so only limited allowance could be made for individual smoking habits.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

HSE BOOKS

© Crown copyright 2005

First published 2005

ISBN 0 7176 6167 9

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CONTENTS

EXECUTIVE SUMMARY V

1 INTRODUCTION 1

1.1 Background 11.2 The semiconductor industry 11.3 Potential exposures 21.4 Previous scientific studies 2

2 AIMS AND OBJECTIVES 4

2.1 Overall aim 42.2 Study objectives 4

3 METHODS 5

3.1 Overview 53.2 Data required for cohort study 53.3 Plant visits 73.4 Other information gathering methods 83.5 Statistical methods/power calculations 93.6 Study publicity 10

4 RESULTS 11

4.1 Summary of information collected 114.2 Cohort identification 114.3 Occupational information 164.4 Exposure estimation 19

5 IMPLICATIONS FOR FURTHER STUDY 23

5.1 Introduction 235.2 Cohort identification 235.3 Job information 255.4 Exposure information 265.5 Statistical power calculations 275.6 Risks to carrying out further study 295.7 Comparison with USA feasibility study findings 29

6 CONCLUSIONS 33

7 REFERENCES 35

8 ACKNOWLEDGEMENTS 37

APPENDIX 1: PRO-FORMA FOR PLANT VISITS 39

APPENDIX 2 : QUESTIONNAIRES FOR SMALL AND CLOSED PLANTS 45

APPENDIX 3: ANNOUNCEMENT TO WORKERS 69

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iv

EXECUTIVE SUMMARY

Introduction

In 2001 the Health and Safety Executive (HSE) reported an investigation into the possible occurrence

of work-related cancer among current and former workers at a semiconductor plant in Scotland. The

investigation was a response to developing concerns about cancer, particularly as expressed by a local

worker support group. The results of the investigation were inconclusive, and the report included a

recommendation that ‘There is a need for a wider industry investigation…’. The HSE therefore

commissioned a feasibility study to investigate whether there is sufficient information on current and

past employees in the industry to provide a large enough cohort for an informative study to proceed.

This report presents the findings of the feasibility study.

Objectives

The objectives of the study were to (i) visit semiconductor plants and inspect records that would allow

cohort identification, characterisation of past exposures and other individual data, such as smoking

habits; (ii) assess and describe the availability, completeness and quality of these records; (iii)

interview relevant past and present staff to obtain a picture of the processes employed at the factory

over different time periods; (iv) make recommendations on the feasibility of conducting a cohort

study in the industry and (v) perform sample calculations for the power of such a study, under suitable

assumptions, to detect and quantify occupationally increased risks of selected cancers.

Methods

The richest sources of data for a potential cohort study are plants that have been in existence for a

reasonable length of time and have employed large numbers of workers. Based on information

provided by the HSE and DTI, the research team compiled a list of those companies which had been

established at least 10 years previously and had employed, at their peak, at least 100 workers. The list

of plants to be visited by the research team was drawn from this list of companies. A total of eight

such plants were visited during the study.

Each plant was visited by an epidemiologist and an occupational hygienist. Prior to the visits taking

place, a ‘pro-forma’ for the visits was sent to each plant, which briefly explained the reasons behind

the visit, how long the investigation would take and who would be carrying out the visit. It also

included a list of the kinds of information the researchers would be collecting. This greatly enhanced

the effectiveness of the visits. The visits all followed a similar pattern which typically involved an

introduction and brief overview of plant history and processes, a tour of the wafer fabrication facility,

a discussion with a member of Human Resources staff about number and scope of personnel records

held, a discussion with a member of Occupational Health Staff about number and scope of health

records held and discussion with hygienists, safety personnel and long-serving employees about the

industrial history of the plant, hygiene monitoring practices and use of chemicals. Following each

plant visit a detailed report was written and submitted to the plant for factual correction and addition

of other relevant information.

In addition, information was requested from smaller and more recently opened plants by means of a

postal questionnaire. Where sufficient contact details could be obtained, postal questionnaires were

also sent to all companies that had previously operated plants now closed. Completed questionnaires

were received from five of the smaller/more recently opened plants and from none of the closed

plants.

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Results: Cohort Identification

Based on the site visits and postal questionnaire responses, it is estimated that there is a potential

study cohort of 12,000 workers with sufficient information to distinguish work experience in wafer

fabrication areas or elsewhere (fab/non-fab). These consist of 5,950 fab workers and 6,050 non-fab

workers; and approximately 5,000 current workers and 7,000 former workers. It is likely that a small

subset of these records refer to duplicate entries, primarily for workers who left the industry and

subsequently rejoined and were given a new personnel record. Assuming that around 5% of records

were duplicates would imply a cohort of 5,653 fab workers and 5,747 non-fab workers. Identification

information is available for a further 6,000 workers, but it would not be possible to classify these

individuals according to whether or not they worked in the fabrication area, and they could therefore

not contribute to internal comparisons.

Records of current workers are likely to be complete for all those working at the plants, and in almost

all cases this completeness can be checked by cross-reference to computerised payroll records.

Additional checks for completeness of identification of current employees can be done through cross­

checks with health and training records at most plants and with pension records at around half of the

plants.

For most companies, records of former workers were reported to be complete for all workers who had

ever been employed by the company. In some instances, however, older records of former workers

were no longer available and in at least one company, leavers’ records were retained only for 10 years

after date of leaving. In addition, where sites had been owned by more than one company over the

years, almost invariably records were unavailable for former workers who had never worked for the

current company. Overall, in any cohort study, there would inevitably be some incompleteness in the

identification of a population of former workers, and this would be focused primarily on those who

had worked in the industry in its early days, a group of high interest in any cohort study.

Results: Occupational and exposure information

For all identifiable cohort members, total length of employment at the plant could be extracted from

these records and, as noted above, for around 12,000 cohort members it would be possible to

subclassify each individual according to whether they had ever (or never) worked in the fab area. The

length of time spent working in fab areas and the calendar periods in which this took place would also

be available for the vast majority of these workers. However, in the many cases where this

information is available only in paper records, occupational histories would need to be reconstructed

from a series of letters, promotions, changes in pay scale, changes in clock number etc. which are

included among all the documents stored in the personnel files. It is likely therefore that the

categorisation would differ in reliability both between plants and over time, i.e. between more recent

and older occupational records.

All plants could provide some form of historical timeline for plant development, which typically

identified the commissioning and decommissioning of fab areas and changes and developments in

production processes and products manufactured. Detailed information is also held at all plants of the

chemicals currently used, and it is understood that these have changed very little over time, although

little information was available on where in the plant each chemical had been used. Limited amounts

of personal or static air sampling took place in all of the plants, often as annual or one-off monitoring

exercises. Some swab sampling for arsenic also took place, typically only in recent years. It was

reported that exposure levels generally were very low, and exposure of workers well controlled.

Historic accident and incident reports were kept by more than half of the plants and these could

provide information on any specific occurrences of potential exposures.

For the majority of the study cohort it should therefore be possible to link individual occupational

histories at the level of time and calendar periods spent working in the fab area, to approximate

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technology eras at each plant. This information could then be compared with whether or not arsenic,

chromium or antimony compounds were being used during these time periods. Information would be

available on what other chemicals were likely to be being used in the plant (based on current data

only) but it would probably not be possible to associate their use with fab and/or non-fab work.

Implications for further study

The current study has shown that it would be feasible to carry out a cohort study of semiconductor

plants across Britain, based on our best knowledge of the identification records and occupational

details which currently exist for potential study participants. The findings of this review show that the

kinds and extent of records held in the semiconductor industry are very similar to those found in

multi-centre cohort studies in other industries. Statistical power calculations show that a study of a

cohort of around 12,000 subjects should have reasonable statistical power to detect an excess risk in a

common cause of death (80% power to detect a relative risk of around 1.8), but relatively poor

statistical power to detect excesses in rarer causes.

Feasibility includes access to these records for research purposes and while access to records of

currently employed workers should be straightforward, there are a number of issues to be addressed

under the Data Protection Act regarding access to records from former workers, or from plants or

companies which are no longer active in the semiconductor industry, held at the company concerned

or in central documents archives. This would need to be resolved before any further study could

commence. In addition, extraction of information, particularly occupational data, from paper files is

likely to be a time-consuming and costly task, and it is possible that the level of detail and

completeness of information stored (and extracted) would differ between plants and between calendar

periods within plants.

We conclude that, provided access to the data records can be agreed with the companies and with

Data Protection custodians, it would be feasible:

1. to construct a study of a reasonably representative cohort of a minimum of 12,000 workers

from the UK semiconductor industry;

2. to trace their mortality and/or cancer incidence within UK national systems;

3. to carry out analyses comparing the mortality or cancer incidence within the cohort with

standard national or regional age- and sex-specific mortality rates for chosen causes;

4. to carry out analyses making comparisons internal to the cohort, distinguishing work

experience in the fab/non-fab areas, and further distinguishing these by calendar periods

representing the presence of different hazards;

5. to carry out only limited analyses that adjusted for the strong effects of smoking on certain

risks.

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viii

1 INTRODUCTION

1.1 BACKGROUND

In 2001 the Health and Safety Executive (HSE) reported an investigation into the possible occurrence

of work-related cancer among current and former workers at a semiconductor plant in Scotland

(McElvenny et al, 2001). The investigation was a response to developing concerns about cancer,

particularly as expressed by a local worker support group. The report concluded that “Our results,

though inconclusive, reinforce the concerns that prompted our investigation. The findings,

particularly those relating to lung cancer, need to be treated very seriously. They raise the possibility

of a work-related risk of cancer, but more detailed studies will be needed to clarify this.” (McElvenny

at al, 2001; page ix). Further details on the findings of the study are given in section 1.4 below.

In addition, the report included a recommendation that “There is a need for a wider industry

investigation … so that the overall cancer experience of all workers in the industry can be

characterised” (McElvenny et al, 2001; page 38). The logic behind this recommendation was that,

even with further investigation at the plant, it might not be clear whether the risk was or was not

related to work in the plant. Characterising the cancer experience in the industry as a whole would

help to resolve this question. Possible extension of a study to semiconductor plants across Europe

would also strengthen the power of the study to detect any associations.

The HSE has therefore commissioned a feasibility study to investigate whether there is sufficient

information on current and past employees in the industry in Great Britain to provide a cohort that is

large enough for an informative investigation to proceed. This report presents the findings of this

feasibility study.

1.2 THE SEMICONDUCTOR INDUSTRY

Texas Instruments produced the first integrated circuit in 1959 and since then the semiconductor

industry has seen the constant development of new and improved production processes. In 1964

Gordon Moore, the founder of Intel and one of the pioneers of the industry, predicted that the density

of integrated circuits would double every 18 months. His prediction has remained a remarkable

predictor of the pace of change in semiconductor manufacture. The increasing density of electronic

components on a chip has meant that the size of individual features on the chip has decreased steadily

and with this the need for a cleaner manufacturing environment has increased, particularly in relation

to particulate pollution. Dirt deposited on the surface of a semiconductor device can cause a short-

circuit, and as the component size has reduced so the size of the particles that can cause a defect has

also decreased. This has stimulated the introduction of highly controlled clean room technology in

the industry.

There are three basic stages involved in the manufacture of semiconductor integrated circuit devices:

crystal growth and wafer preparation; wafer fabrication; and packaging of the device into its final

form. For most semiconductor devices used today the starting material is silicon, which is grown into

a crystal with specific structural and electrical properties. These are then cut into thin disks or wafers

that are the basis of the fabrication process. There may be several thousand steps required to fabricate

the chip, which may contain thousands of discrete microchips. The fabrication process can be divided

into two stages: front end of line, where the transistors and other electronic devices are formed, and

back end of line, where the devices are wired together with conducting layers. Following fabrication,

the chips are tested and then the individual chips are separated and wired into protective packaging.

The historical development of the semiconductor industry can be broadly divided into five decades.

During the 1950’s the industry was manufacturing individual semiconductor devices such as

transistors and developing the technology for integrated circuit manufacture. Until the mid-1950’s

most semiconductor devices were made from germanium and only later did the advantages of silicon

1

technology become evident. Between 1961 and 1970 there was a rapid expansion of the number of

companies involved in manufacturing microchips. There was a change from what had mostly been

laboratory batch processes to high volume manufacturing lines.

The 1970’s saw the introduction of many technological innovations and moves towards automation of

some of the processes. There were great improvements in the construction and operation of the clean

room environments. However, during the 1980’s it became clear that one of the main sources of

particulate contamination in clean rooms was the people, and it was for this reason that process

automation was more extensively developed. By the early 1990’s the size of individual chip

components had decreased to less than 1 µm (1 micron), with hundreds of thousands of components

on a chip. By the end of the decade the number of components per chip had increased to tens of

millions. These changes were achieved by improvements in the lithographic processes used to form

the chip.

A chronology of the industry can be found at http://www.sia-online.org/abt_history.cfm .

1.3 POTENTIAL EXPOSURES

Manufacture of semiconductor chips involves many process steps and the majority of these steps use

chemicals. Large quantities of acids, bases and solvents are used. Several substances or agents that

have been present or used in the semiconductor industry are known or suspected carcinogens.

Specifically, antimony trioxide, arsenic and arsenical compounds including arsine, asbestos,

chromium trioxide and chromic acid, and ionising radiation are all associated with lung cancer to

varying degrees. Whether or not these are associated with an increased risk depends on the intensity

and duration of exposures experienced by people in the course of their work.

Exposures in the industry are generally well controlled. An HSE programme of inspection of

manufacturers of semiconductors in Great Britain in relation to carcinogens was undertaken as a

response to the findings of the study at the Scottish plant. The report concluded that overall the level

of compliance with legal requirements was comparable with many other manufacturing industries

with some very good practice and some areas where improvements could, and sometimes should, be

made (HSE, 2002). Most companies were close to or complied with minimum legal requirements,

although specific issues were raised regarding the use and maintenance of local exhaust ventilation,

assessment and control of carcinogens during cleaning and maintenance, and the manual handling and

dispensing of hazardous chemicals.

In addition, it has been suggested from other studies that prolonged night shift work might be a risk

factor for breast cancer, and shift work among women is prevalent throughout the semiconductor

industry.

1.4 PREVIOUS SCIENTIFIC STUDIES

As mentioned earlier in this report, an investigation of cancer among current and former workers at a

Scottish plant, National Semiconductor (UK) Ltd, Greenock, was published by the HSE (McElvenny

et al, 2003). This study comprised a mortality study of 4388 workers and a cancer registry study of

4383 workers, with an average length of follow-up for the mortality study of 12.5 years. Results of

this study showed that total cancer registrations were close to expected levels for men and for women.

Four specific cancers showed findings which raised some concerns. There was a statistically

significant excess of lung cancer among women, based on 11 cases (Unadjusted Standardised

Registration Ratio (SRR) for total females, 373 (95% CI 186 to 668), deprivation-adjusted SRR 273

(95% 136 to 488)) which was approximately three to four times as many as expected, and an excess of

cases of female stomach cancer, though based on only 3 cases, was approximately four to five times

as many as expected and was of borderline statistical significance (Unadjusted SRR for total females,

491 (95% CI 101 to 1435), adjusted SRR 438 (95% 90 to 1281)). Non-significant excesses of female

breast cancer, based on 20 cases (Unadjusted SRR for total females, 125 (95% CI 76 to 193), adjusted

2

SRR 134 (95% 82 to 206)) and of male brain cancer were also found (approximately 4 times as many

brain cancers as expected, based on three cases, unadjusted Standardised Mortality Ratios (SMR) 401

(95% CI 83 to 1172), and there was a further non-fatal case. Some aspects of the data, including short

latency for the development of the disease, raised questions about the likelihood that the observed

excesses were work-related and it was concluded that further investigations were necessary.

The mortality and cancer morbidity experienced by a cohort of 1,807 male and female employees

from a semiconductor plant in the West Midlands were investigated by the University of Birmingham

(Nichols and Sorahan, 2004). This study found significantly elevated morbidity for cancer of the

rectum for males (SRR 284, 95% CI 104 to 619) and the total study cohort (males and females

combined) (SRR 199, 95% CI 120 to 310) and malignant melanoma for females (SRR 221, 95% CI

110 to 396) and the total study cohort (SRR 217, 95% CI 112 to 379), and significantly elevated

morbidity for cancer of the pancreas in female employees only (SRR 226, 95% CI 108 to 415).

Analyses in relation to occupation were limited by the non-availability of work histories, but analyses

in relation to year of hire, period from first employment and duration of employment did not suggest

any relationship with occupation. There was no evidence of any excess in the cancers indicated by

the NSUK report, and more specifically, there was a significant deficit of deaths for female breast

cancer. It should be noted, however, that the lack of detailed exposure information in each of the

studies makes comparisons between their results inconclusive. The authors note that the fact that the

“excess risks reported by one study are not replicated by the other….may indicate that occupational

exposures in the two facilities are very different”.

In 1999, the Semiconductor Industry Association (SIA) created an independent Scientific Advisory

Committee (SAC), to review available scientific information and determine if there is any evidence of

increased cancer risk among wafer fabrication workers in the U.S. semiconductor industry. A review

of processes and chemical use in these settings was also undertaken. It was reported that there was no

affirmative evidence of an increased cancer risk among semiconductor workers but that there was

insufficient evidence to conclude that exposures to chemicals and other hazards in wafer fabrication

have not or could not result in measurably increased risk of one or more cancer types. It was therefore

recommended that the SIA conduct a retrospective epidemiology study, if feasible, to evaluate

potential cancer risk to semiconductor workers (Cullen et al, 2001).

Following a feasibility study similar to the present exercise, a study of cancer risks in semiconductor

workers for IBM was begun in the late 1990s. The report from this study is expected imminently, but

has not yet been published.

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2 AIMS AND OBJECTIVES

2.1 OVERALL AIM

The overall aim of the study was to investigate whether there is sufficient information on current and

past employees in the industry to provide a cohort that is large enough for an informative

investigation to proceed. In particular, it was noted that:

1. This would involve understanding the personnel information held by each of the semiconductor

industry factories in Great Britain;

2. The information would need to be assessed in terms of its availability and quality (including

accuracy, completeness and representativeness) to allow workers to be flagged at the National

Health Service Central Registers for death and cancer registration data;

3. This would include, where appropriate, an assessment of any apparent shortfalls or errors in the

data that might be corrected to allow a study to proceed;

4. Any additional information that is readily available that could inform the retrospective cohort

study such as data on smoking, job histories and potential for deriving exposure assessments

should also be documented, together with brief descriptions of the main production processes

employed at the various factories and the changes in these over time.

If a study of cancer in the British semiconductor industry was (i) found to be feasible and (ii)

considered likely to be informative about the risk of cancer from working in the industry, then an

additional aim of the study was to carry out statistical power calculations for selected causes of death.

2.2 STUDY OBJECTIVES

The specific objectives of the study were to:

1. Visit semiconductor plants and inspect records that would allow cohort identification,

characterisation of past exposure patterns, and any other individual data (e.g. smoking habits);

2. Assess and describe the availability, completeness and quality of all these records;

3. Interview relevant past and present staff to obtain a picture of the processes employed at the

factory over different time periods, and record any important changes that would influence

exposures to employees;

4. Make recommendations on the feasibility of conducting a cohort study in the industry;

5. Perform sample power calculations for the power of such a study, under suitable assumptions,

to detect and quantify occupationally increased risks of selected cancers;

4

3 METHODS

3.1 OVERVIEW

The richest sources of data for a potential cohort study are plants that have been in existence for 20 or

more years and have employed large numbers of workers. Based on information provided by the HSE

and DTI, the research team compiled a list of those companies which had been established at least 10

years previously and had employed, at their peak, at least 100 workers. The list of plants to be visited

by the research team was drawn from this list of companies. In addition, information was requested

from smaller and more recently opened plants by means of a postal questionnaire. Postal

questionnaires were also sent to all closed companies for which sufficient contact details could be

obtained, where records were held and where the plants agreed to participate in the survey.

Information gathered from these companies was used to estimate the size of cohort available for study

and to assess the quality and possible completeness of the data. The level of occupational information

available for individual workers was also determined, as was the information available on changes in

process and hence potential exposure levels. Finally, statistical power calculations were carried out to

assess the power of any potential cohort study to detect increased incidence of various cancers. More

detail on each of these aspects is given below.

3.2 DATA REQUIRED FOR COHORT STUDY

3.2.1 Identification data

Tracing of mortality and cancer registration events for research studies is carried out through the

National Health Service Central Register (NHSCR), and arranged through the Office of National

Statistics (ONS) for England and Wales, or through the General Register Office (GRO) for studies

where the population is primarily Scottish. The success of matching individuals in a study population

to events in the NHSCR depends partly on the identification details available for matching. The ideal

situation is where the researchers can quote full surname and forenames, date of birth and National

Health Service number. However, the NHS number is seldom available in personnel or occupational

health records. Most occupational studies can provide the National Insurance number, but this is not

held in the NHSCR, and a comprehensive database which links these two identity numbers does not

exist.

Most occupational cohort studies therefore seek to match on full name and date of birth, and to

distinguish multiple matches by location of residence, e.g. last known address or location of

employment. With suitable data, a tracing exercise can achieve vital status determination in over 95%

of a cohort, but partial data make tracing much more difficult. It was therefore crucial to establish the

level of detail to which these identifying data are held, and the consistency of this information across

different sources at the same plant (e.g. personnel and payroll records).

3.2.2 History of jobs held

The possibilities for statistical analysis in any occupational study depend, inter alia, on the

distinctions, if any, that it is possible to make between individual exposures within the industry.

Where no distinctions are possible, the study may be necessarily limited to comparison of observed

rates with those expected from routine population statistics collected nationally or (preferably) locally.

This circumstance is relatively rare, and it is usually possible at least to establish the length of each

worker’s employment (or time since first employment) and to stratify the analysis or to compare

observed rates on this variable; and it may be possible to do much better than this if the necessary

data are available in the records.

5

However, job and work area distinctions are important less for their own sake than for making

distinctions between occupational hazards present and levels of exposure to them. The large-scale

changes in process that have occurred in different parts and periods of the semiconductor industry

offer potential for important contrasts in exposure. An important aspect of the feasibility study was

therefore an assessment of the extent to which these could be matched to industry records or

knowledge of processes and the exposures involved. Likewise, an assessment of the information

available from records or memories of the history of processes and about exposures (directly or

through a retrospective exposure assessment exercise) is useful but the essential judgment is whether

the level of detail possible matches that in the job histories. An information deficit in either job

histories or process descriptions will thus reduce the level to which analyses may probe, and an

important part of the feasibility assessment was to describe the level at which this matching could be

carried out.

Typically, employment histories detailing jobs held with start and finish dates, if they exist, will be

found in personnel records, and sometimes in training or other records. The essential questions were

the level of detail at which these jobs are distinguished, and whether the distinctions made are likely

to distinguish importantly different exposures.

3.2.3 Exposures and process descriptions

Any attempt to create distinctions between exposures of cohort members, individually or in groups,

will depend on the availability of information about the exposures in the various work processes and

areas, and how these have changed over time. The ideal situation is where measurements of exposure

have been made and retained, but this is rare. However, it was essential to ascertain at each plant

exactly what distinctions are possible, and to link these findings with the level of detail at which job

histories are held.

During the feasibility study we aimed to tentatively identify the duration and extent of exposure

within the plant of all of the following:

x arsenic compounds, including arsine;

x chromium compounds;

x antimony compounds;

x ionising radiation and

x work at night.

It was acknowledged that these might not be the only exposures of interest, but it was felt that

attention to this list would give useful pointers to the potential to identify relevant exposures.

This information would allow the provisional classification of the history of production at each plant

into technological eras. Note that although these are broadly representative of different decades the

actual categorisation would be based on the changes in technology. These eras could be:

x Early era, before approximately 1960. Characterised by laboratory scale batch type

production.

x Expansion era, approximately from 1960 to 1969. Development of high volume

manufacturing lines.

x Automation era, from 1970 to 1979. Characterised by automation of the production and

improvements in clean room environments.

x Modern production era, from 1980 onwards.

6

3.2.4 Data on occupational exposures outside the factory

Data on employment at other semiconductor facilities might be available if the prior employment was

at a factory subsequently absorbed by the current employer. In such a case, it would be useful to

ascertain and describe the extent to which such data exist.

Prior exposures to carcinogens in employments outside the semiconductor industry remain possible,

but it is unlikely that the current factory records would give details of these, and we expected that any

judgment on feasibility would be made in the knowledge that data on prior occupational hazards

would not be available. This is unlikely to be a serious lack unless a large percentage of the

workforce had previously worked in a single risky industry.

Some of the factories may be located in areas where there can be environmental or para-occupational

exposures to hazardous substances, particularly to asbestos. These exposures may contribute to

increased background rates for cancers and some knowledge of surrounding industries may help with

the interpretation of the results from any epidemiological study in the semiconductor industry.

3.2.5 Other personal data

For a study where there is already interest in lung cancer risks, it is clear that the existence of data on

individual smoking habits, if available, would be of great value. In British industries, it is unusual for

such data to be held in personnel records. Sometimes, where occupational medical provisions exist,

smoking habits may be recorded in the medical records. Enquiries about the availability of such

smoking data were made during the feasibility study.

3.3 PLANT VISITS

3.3.1 Selection of plants

The tender specification listed some 38 plants, with another 25 known to be closed. A plant at

Greenock that had already been studied by the HSE was not included in this study. Those plants that

were still open varied widely in terms of location, size and length of operation. Given the latency

from first exposure for cancers and the relative rarity of the disease in persons of working age, it was

clear that information about industry-based risks would be concentrated in large plants that have been

open for many years, and that smaller plants and plants recently opened would add relatively little

information if any.

Using information appended to the original Invitation to Tender (ITT), 13 plants were identified for

visits. These were chosen using the following criteria:

x Plant started operating in 1995 or earlier;

x Plant had a known peak number of employees which was greater than 100.

Discussions with the industry revealed that two of these plants had subsequently closed, and one of

them fell outside the selection criteria as its peak number of employees was less than 100. This left a

list of 10 plants to be visited; industry representatives provided contact names for 9 of these.

These 10 plants were contacted by telephone so that mutually convenient dates for visits could be

arranged, and visits were set up for 8 of the 10 plants. The remaining two plants were contacted by

telephone. One of these informed us that, due to a recent takeover, they had very few records on site

and did not think that a visit would be worthwhile. For the second remaining plant, no contact

information had been provided on the original list of plants. A name was obtained from the National

Microelectronics Institute (NMI) and a phone call made to the plant. Management at the plant were

happy for the plant to be included in the study, but after further discussions between the plant, IOM

and NMI it became apparent that the plant fell outside the size criteria for inclusion in the study.

7

In total, therefore, visits were arranged at eight plants and these were carried out between 11 August

and 26 October 2004. Each plant was visited by the same occupational hygienist from the study team,

and by one of two study team epidemiologists. During the course of the visits, it was discovered that

two of these plants had changed ownership in the past two or three years, although semiconductor

production had taken place on the same site for some years previously under different ownership.

3.3.2 Pro-forma

Prior to the plant visits taking place, a ‘pro-forma’ for the visits was drawn up. This document briefly

explained the reasons behind the visit, how long the visit would take and who would be carrying out

the visit. It also included a list of the kinds of information the researchers would be collecting during

the visit. The pro-forma was sent to each of the plants in advance, and allowed the preparation of

responses to the information requests before the visit took place. This greatly enhanced the

effectiveness of the visits. A copy of the pro forma is shown in Appendix 1.

3.3.3 Administration and reporting of site visits

Members of the research team contacted each of the plants to be visited, to establish liaison with the

relevant staff, and arrange suitable dates for the visits to take place.

Each plant visit followed a similar pattern, and would typically involve:

x An introduction and brief overview of plant history and processes;

x A tour of the wafer fabrication facility – often the researchers went inside the wafer fab,

occasionally they would be given an external tour where they could see processes through

viewing windows;

x A discussion with a member of Human Resources staff about number and scope of personnel

records held;

x A discussion with a member of Occupational Health Staff about number and scope of health

records held;

x Discussion with hygienists, safety personnel and long-serving employees about the industrial

history of the plant, hygiene monitoring practices and use of chemicals.

Following each plant visit a detailed report was written and submitted to the plant for factual

correction and addition of other relevant information. Thereafter a final revised version was created.

3.3.4 Contract workers

During the study, particular interest was noted in whether it would be possible to identify contract

workers at the plants for inclusion in any potential cohort study. The research team therefore ensured

that during each plant visit, information on contract workers and the availability of personnel records

held for them, was obtained.

3.4 OTHER INFORMATION GATHERING METHODS

As noted above, the feasibility of a full-scale study depends crucially upon the possibility of obtaining

the necessary data from the informative factories (large and open for longer) at which visits took

place. Similar visits to smaller factories would take almost as much time as visits to large sites, and

such visits were unlikely to be cost-effective. It was therefore decided that assessment of the smaller

or newer plants would be made by telephone calls or other long-distance communication. Assessment

of closed plants was also done by remote correspondence.

Two self-completion questionnaires were designed, one for small plants and one for closed plants.

These were based on a simplified version of the plant visit ‘pro-forma’ (Appendix 1), and were

8

designed using the information gained during the site visits to pinpoint the most vital data issues. The

study ITT listed 38 operating plants, of which 5 were excluded:

x One had closed and its records were held by one of the plants visited by the study team;

x One had been built but never commissioned;

x One had opted out of the feasibility study;

x One had gone into administration;

x One had been the subject of the original HSE investigation.

Of the remaining 33 plants, 11 were investigated as part of the programme of visits and industry

sources indicated that 7 were now closed. The remaining 15 open plants were included in the survey

of smaller plants. Contact details were also obtained for a total of fifteen closed plants. Copies of the

two questionnaires are reproduced in Appendix 2.

Attempts were made to contact each plant included in the survey by telephone. Where this was not

successful, email contact was instigated where available. Contacts at the plant were asked if they

would be willing to complete a postal questionnaire, and if they agreed a copy of the questionnaire

was sent to them, along with a stamped addressed envelope for their return. In some cases, where

only a postal address could be identified, the questionnaire was mailed without any prior contact with

the plant. Reminders were sent to those companies who did not return the questionnaire within a few

weeks of the mailing. Plants were also encouraged by industry and the NMI to participate in this

phase of the study.

Of the 15 smaller plants, questionnaires were sent to 10 participants. One plant, which was now

concerned only with test and assembly, and which not had a fab area for over 30 years, referred the

study team to another plant owned by the same company. Contacts at this plant were unable to

provide any further information. Three plants were undecided about whether or not they would

participate in the questionnaire survey, and did not respond further to the study team. At the final

plant it did not prove possible to make contact with the Health and Safety Manager by telephone or

email.

Contact with the closed plants proved much more difficult. Some contact information was received

from the study Scientific Advisory Group and sponsors, and further information was found through

searches of the Internet and of business directories. Usable contact details were obtained for 15

closed plants of which 10 were sent questionnaires. Of the remaining five plants, two reported during

the telephone contact that they did not hold any records, and two plants an email address was

provided for a named contact, but no response was received and at the final plant it did not prove

possible to make contact with the Health and Safety Manager by telephone or email.

In addition, information was obtained during the plant visits about older records that currently are, or

soon will be, stored in central archives. Two archives specifically mentioned were Marconi archives

in Coventry and Motorola archives in Basingstoke. Information was sought on the availability of

these records to the study team. To date, no contact has been achieved with the owners of these

archives and it is not known whether or not the records would be available for inclusion in a cohort

study.

3.5 STATISTICAL METHODS/POWER CALCULATIONS

If a study is judged feasible on the basis of the availability of the necessary data, then the study team

was required to calculate the power that such a study would have to detect and quantify any effect of

occupational exposure within the industry. This was based on estimates of the expected numbers of

deaths or incident cases. To do such calculations in detail would require information on the

distributions of age and length of exposure in the study population, and it was unlikely that these

would be available at the individual level. However, the feasibility study should be able to produce a

broad indication of the numbers employed at the plants and some basic occupational information,

9

allowing the calculation of statistical power using some simplistic assumptions and combining them

with published rates for the cancers of interest. These calculations, while necessarily approximate,

will act as a guide to the power of a full-scale study.

3.6 STUDY PUBLICITY

To act as a focal point for information on of the study for the management and workers of the

semiconductor plants, the Health and Safety Executive added details of the study to their webpage:

http://www.hse.gov.uk/statistics/live/#semiconductor

This website contained details of the study proposal, a brief background information leaflet and a

copy of a study announcement which was distributed to current workers in the industry before the

plant visits took place. A copy of the workers announcement in shown in Appendix 3. Study

progress reports were also added to the website during the course of the study.

10

4 RESULTS

4.1 SUMMARY OF INFORMATION COLLECTED

The study team visited eight plants. Following these visits, a report of the discussions was sent to the

company management for comment, factual corrections and addition of other relevant information not

collected during the visit. At the time of writing this report five companies had returned the reports

with comments and additional information where requested by the study team. Information from the

other three companies is based on the original reports as prepared by the study team.

Extensive information was collected during these plant visits, including copies of health

questionnaires, layout of personnel records, lists of job codes used etc. Detailed reports were written

for each site visit, and these contain detailed histories of site processes, details of occupational

hygiene monitoring systems and of personnel records. To maintain confidentiality these individual

reports have not been included in this report, although it is intended that they will be made available

(with the agreement of the relevant companies) as a resource to the study team if an industry-wide

study takes place. The following sections provide a brief summary of the information available, and

we have focused on those data items most critical for making judgements on the viability of a future

cohort study.

Information was also requested from 10 smaller and more recently formed companies, and from from

the successors of 10 companies now closed, by postal questionnaire. At the time of writing,

completed questionnaires had been received from five open plants and none of the closed plants.

These questionnaires are summarised, where relevant, in the sections that follow.

4.2 COHORT IDENTIFICATION

4.2.1 Cohort identification information and cohort size

Current workers

All eight plants visited maintained personnel records which included the key items of identification

information for current workers including full name, address, date of birth and National Insurance

number (National Health Service number was not routinely collected at any of the plants). Across the

eight plants, records existed for approximately 4,250 current employees. Identification information

on all these workers was held electronically and could easily be extracted for the purposes of cohort

identification.

Responses to the postal questionnaire indicated that all five responding companies also held the same

key items of identification information for their current workers, of which there were a total of 752

across the five companies. Personnel information at these sites was reported to be held on a mixture

of paper and computer records at four of the companies and on computer only at the fifth company.

Leavers

At four of the companies visited, records are kept for all ex-workers who had ever worked for the

company at that site. Two of these companies had taken over the sites relatively recently and so held

records on fewer than 50 workers who had left since the takeover took place. The other two plants

held records going back thirty or more years. At the other four plants leavers records are available as

follows:

x Full records from 1992, less complete from 1982;

x No records held for those who left prior to 1990 - leavers records are held for 10 years after

date of leaving;

11

x Records available from 1988;

x Records available from 1979.

Where companies had changed hands over the years, only in one instance were any records available

from workers in previous companies who had not transferred to the current company at the time of

transfer. Other companies reported the transfer of these records from previous owners to central

archives or other sites owned by the original site owners.

Overall, six of the eight companies visited reported holding records for a total of approximately

12,500 former workers, 6,000 of whom were from one of the plants. One company was unable to

determine how many leavers’ records were held, though it was believed that records dated back to

1971. The final company reported holding records for a total of 6,000 ex-workers but it was unclear

whether these records referred to British employees only or to employees of the company worldwide.

Identification information for leavers was generally similar to that held for current workers at the

plants. At the more recently opened plants, all records of leavers were stored electronically – this

covered around 1,000 individuals. At the other plants records were held partially on paper and

partially electronically (usually electronically from the late 1990s and paper before that).

Responses to the postal questionnaire indicated that all five companies replying held records on

leavers containing the same identification information as for current workers. Two companies

retained leavers records ‘indefinitely’, one company had kept records from 1996 and one from 1997.

The final company held records for all leavers to date and planned to retain records for at least five

years. Four companies reported approximate numbers of leavers’ records held and these totalled

around 615 individuals. Three of the companies held leavers’ information on paper only and two held

leavers’ information on paper and computer.

Typically paper records would be held in filing cabinets, often arranged alphabetically by name.

Records would often comprise a detailed personnel file for each worker. Extraction of information

from these records would be likely to be a time consuming process.

Information on a plant by plant basis is summarised in Tables 1a and 1b.

Summary

In summary, from the responses obtained during the study, we estimate that there would be electronic

identifying information accessible for approximately 5,000 current workers and for 1,000 leavers,

with records for up to 12,000 additional leavers available in either electronic or paper files. The

companies were not able to provide exact numbers of paper or electronic records, but as the electronic

records of leavers commenced in the late 1990s, it seems likely that the majority of these 12,000

records are maintained in paper records. In most of the plants the size of the workforce fluctuated

widely over time, dependent on the changing demand for semiconductors in the marketplace. Current

workforces are generally smaller than those employed in the past, and there are some moves across

the industry towards transferring production outside Great Britain.

Six of the plants visited provided some information on the proportion of their workforce who worked

in the wafer fabrication area (‘fab’ workers). This varied among companies from 13% to 70% of

employees. Of the 3,065 current workers in these six plants, an estimated 1,500 (almost 50%) would

have worked in the fab areas at some time during their employment. Historically most of the fab

workers (up to 90% in some plants) were women. This proportion has declined over time, but in most

plants more women than men work in the fab areas, in a proportion of around 2:1. Non-fab workers

in most companies are predominantly men.

12

C

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14

4.2.2 Lengths of employment (start dates)

No specific detail was available on the lengths of employment of those employed at the plants which

were visited. Most plants had 10 to 20 employees who had been employed ‘long-term’, often over 20

years. At one plant, the average length of service was estimated to be 11 years. Only two of the

postal questionnaires contained information on long serving employees. At one company 3 out of 73

current workers had been employed since the plant opened around 20 years ago, at the second

company 25 of 92 current workers had been employed since the plant opened, although this had been

relatively recently.

4.2.3 Cohort completeness

An important aspect of cohort identification is an estimate of how complete the identified cohort

might be. Possible ways of checking completeness were therefore investigated during the plant visits.

At 6 of the 8 plants visited, personnel records could be cross-checked with computerised payroll

records, which therefore provide an up-to-date check on the completeness of the personnel records for

current workers.

Other sources for checking completeness included:

x Pension records: usually electronic, available at 4 plants, contain records for current workers

and some leavers but were not thought to be complete at any plant;

x Health records: usually paper-based, contain details of all current and ex-workers at three of

the plants and only more recent leavers at the other five plants (back to 2000, 1990, 1984 and

unknown at the other two plants);

x Training records: usually electronic, only kept for current workers who had trained for

specific tasks and often held for less than 10 years.

At a subset of the plants, it appears possible to cross-check the completeness of the leaver population

by cross-checking with paper-based health records. At other plants, no comprehensive list is available

although limited cross-checks could be carried out with the incomplete records held in pensions,

health departments and training records. Checking with at least a sample of these additional

information sources would help identify if there were any individuals with, for example, training

records who do not appear on the personnel lists, thus providing an assessment of the completeness of

the personnel records.

Information on potential alternative sources for cohort checking was not requested as part of the

postal questionnaire. However, it was noted that three of the five responding companies held health

records for all current and former workers, the fourth company retained health records for the past

five years, while the fifth company did not hold any health records.

At all plants questions were asked about contract workers. Often contractors are used for cleaning

outside the clean room, security, maintenance outside the clean room and catering. One company

used contract workers as cleanroom operators. The level of information available on contractors

varied across plants. Some held clocking in, security pass or induction records for contract workers.

Typically this information would only be available for recent years. Other plants could identify the

companies that the contractors were employed by, but had no information on identities of individual

contract workers.

Among the five companies responding to the postal questionnaire, four employed contract cleaners in

the fab area and four employed contract workers outside the fab area for security, maintenance and

other tasks.

15

4.2.4 Smoking information

Information on smoking habits is not collected routinely on personnel records. The most likely source

of this information is from health records at the plants. As noted above, some form of health records

were available at all eight of the plants visited, and for four of the five companies responding to the

postal questionnaire. It is understood that health records are available for all current and ex-workers

at six of the plants and for all current workers and a subset of ex-workers at the other six plants.

Two of the eight plants visited reported that they had no smoking information recorded in their health

records, and two plants reported that they held smoking information for all current and ex-workers,

although the wording of the questions used to determine smoking may have changed over time.

These two plants included a total of approximately 1,800 current workers and 6,000 leavers. Of the

remaining four plants, one held smoking information on health records since 1990 and one since

1995. The other two plants reported that some sporadic smoking information would be available but

that it was difficult to know what had been collected during which time periods.

The four companies that completed the postal questionnaire and that had health records, held smoking

information in their health records, three of these for all current and former workers and one held

information covering health records from the previous five years.

4.2.5 Staff turnover

Overall, the number of operators employed in semiconductor fabrication facilities has steadily

declined over the years due to the gradual increase in usage of robotics and automated equipment

resulting in less labour intensive work and changes in technology and product lines.

There are several known instances were employees have left employment at a site, only to commence

employment again at a later date, for example due to redundancies and subsequent recruitment due to

increase in product market forces. Upon re-employment the individual is usually provided with a new

employee number and record and while several companies stated that attempts would be made to

combine both past and current employment records, this is not always undertaken. Additional

difficulties occur if a change in company ownership has occurred as the previous employment records

are held by the previous company owners which lead to difficulty in locating and amalgamating the

records.

One company also noted that they have a policy of deliberately recruiting individuals from other

semiconductors plants and it is felt that this will be common across the industry. It is therefore

possible that individuals may have multiple employment records in a number of semiconductor

fabrication facilities.

As estimates of the numbers of workers returning to employment were not obtained for each company

visited, it is not possible to estimate how many workers in the cohort may be duplicates in this way.

Nor is it possible to estimate how many workers may be duplicates due to being employed by more

than one company. Nonetheless, to avoid a systematic overestimation of the number of workers

identifiable in a potential cohort study, we have assumed for the purposes of estimating the statistical

power of any future study, that 5% of records identified are duplicates.

4.3 OCCUPATIONAL INFORMATION

4.3.1 Job information held

The most comprehensive and consistent source of job information for individuals within each plant

was that which was recorded in personnel records. At all the plants visited, some level of

occupational information was held in these records. Information on current job and department was

held electronically at all companies. Two of the companies visited also held electronic records of

16

changes in job titles and departments from 1998, one company held occupational information

electronically from 1992 and one from 1988.

Older records and records for leavers were generally held in paper files. Extraction of occupational

information from these paper files would be a time-consuming and complex task, most often

consisting of identification among other personnel documents of letters detailing changes in job title,

promotions, departmental changes etc., and using these to reconstruct an occupational history.

Most companies thought that more recent occupational information was much more complete and

reliable than that held going back in time.

4.3.2 Separation of fab/non-fab

At all of the plants visited and at four of the five plants responding to the postal questionnaire, it is

possible to subdivide current workers into fab/non-fab categories for their current job. In 8 plants (5

visited, 3 postal) it is possible to provide more detail about the fab work, either by job within the fab

area or by which fab the worker was employed in. However, the level and type of detail provided

varied widely between companies.

At four of the plants visited, covering a total of over 12,000 workers, all potential cohort members

could be classified according to whether they had ever been fab workers. In most instances, where

subdivision into fab/non-fab workers was possible, the length of time spent in fab/non-fab jobs could

be estimated, although this would need to be reconstructed from letters and forms in personnel files

documenting changes in department over time, and so any such calculations would necessarily be

approximate. It would also be possible to estimate approximate calendar time periods spent in the fab

areas.

In the other four plants, this information was available for more recent occupations but was

unavailable or incomplete in the historical paper records. Thus, individuals who had worked in the

companies more recently (often from the mid 1990s) could be classified according to whether or not

(and how long and when) they had worked in the fab area since that date. However, information

would not be available for jobs they had held prior to that date, nor for workers who had left the

company prior to the recording of this occupational information.

Among the responders to the postal questionnaire, two companies reported that it was possible to

categorise leavers as fab/non-fab workers and three reported that detail was available for leavers on

jobs held within the fab area.

4.3.3 Other occupational detail

Some additional information about workers’ occupations was available in records other than those

held by the personnel department. This was often not collected in such a systematic fashion, but

could be used to cross-check and perhaps augment the basic occupational data. The additional

sources of occupational information varied widely among the eight plants visited, and cannot easily be

summarised. A summary of these sources of information is therefore provided below for each plant to

provide examples of the types of information identified. As with the occupational information, the

most complete and reliable data refers to more recent years.

Plant A: Current place of work is recorded in payroll records. Health surveillance records since 2001

identify maintenance engineers in the fab area (< 50 workers) who undergo urine testing for arsenic

exposure and laser eye checks, and the few operators from one specific fab process who have

undergone blood lead monitoring since 2002. Similar health surveillance was carried out sporadically

prior to these dates. Health records also contain information on current job and department at the time

of each health examination (usually at time of first employment). Electronic training records are

available dating back to 1996, which provide details of the various tasks that process operators have

17

been trained to do. It is compulsory for process officers to be trained and signed off before they can

operate the relevant equipment/process.

Plant B: Training records for an individual and process in a particular area are held locally in that

business area. General training records are held centrally. Training records are available for

operators and engineers. Informal records are kept detailing operators’ competencies which are

updated yearly. These are held locally in specific business areas. It is not known how long any of

these records have been kept for, nor how complete they are.

Plant C: Health pre-employment records (paper-based) contain information on job applied for and

department, and whether the individual has ever worked for the company previously. Workers in the

fab area complete a respiratory questionnaire at time of employment and annually thereafter. This

contains details of current department. Different questionnaires have been used over time and it is not

known if this information was always collected. Health surveillance records are available for

individuals (fewer than 18 people) who worked with ion implanters. This was a one-off surveillance

in 2003. All operators from the wet etching processes had urinary checks for hydrofluoric acid from

mid 1980s to early 1990s. Training records for the past 3 years are available for operators containing

details of induction training and particular process and equipment training. An electronic database is

available detailing operators’ process training and recertification. It is not known what training

records are held prior to this time, nor how complete they are.

Plant D: Pre-employment health questionnaires usually contain details of the individual’s proposed

job title, and the majority of health records should identify fab/non-fab workers but this is not always

possible for older records. Some health surveillance has taken place checking for arsenic exposure.

The methods used have varied over the years, and previously job information would only be recorded

if the individual was found to have elevated levels. More recently job descriptions have been

routinely recorded at the time of the medical tests. Information on arsenic testing is available since

1987 though extraction from paper records would be difficult. Individuals required to wear

Respiratory Protective Equipment (RPE) – emergency response team, those potentially exposed to

arsenic – complete a respiratory questionnaire, which includes information on department and job

title. Prior to 1990 limited detail on RPE use is held and records may only go back to 1987. Training

records are available from the mid to late 1990s in a mixture of paper and electronic systems. All

employees undergo induction training with individuals then receiving appropriate training targeted at

their job.

Plant E: Pension scheme records hold length of service with the company but no other occupational

information. Individuals employed as equipment and facilities engineers undergo annual medicals,

these have been carried out for the past 20 years (since1984). A one-off survey for urinary levels of

arsenic was carried out in 2002 for selected fab workers and results are held in their medical records.

Training records are held for the past 2-3 years. It is highly unlikely that any training records older

that 5 years would be retained.

Plant F: All workers complete a pre-employment medical which includes an Occupational Health Job

Requirements form which includes information on the individual’s operation and group number. This

information is also recorded on each employee’s annual health surveillance questionnaire. Health

surveillance is carried out for workers with potential exposure to a number of substances including

arsenic, mercury and beryllium. It is not clear how far back these records go. A database of training

records is held which goes back to 1993. Operators receive tool specific training and records include

information on the process stage and description and the date training was completed. Records from

1996 onwards are available for all present and previous company employees. All employees also

receive induction training.

Plant G: There is a limited number of health surveillance records for specific groups of employees

including the emergency response team, acid etch process operators working with hydrofluoric acid,

employees exposed to chromium 6 or arsenic. These are available for the last 3-4 years. Each

18

employee receives departmental induction training and training records are held by the Human

Resources Department.

Plant H: Pre-employment medical questionnaires are completed for all workers. These include

department, proposed employment and clock number. Paper based health records from 1984 contain

clock number, department and occupation. Intermittent health surveillance for arsenic exposure was

carried out for some fab workers between 1979 and 1984. Training records have been held for

operators for the last 6-7 years. These contain details of any specific health and safety training,

process and tasks training. Fab operators are trained to operate particular processes although an

individual may be trained to undertake a task that they may not actually do.

4.3.4 Shift patterns

In all of the plants visited, shift patterns had changed over time. Many of the plants currently operate

12-hour shifts either as 4 days on, 4 days off or 2 days on, 2 nights on, 4 days off. Several of the

plants operate 24 hours a day, 7 days a week with others introducing night shifts at times of high

production demand. Information on individual shift patterns is usually available for the same time

periods as there exist good occupational records. At all plants, information on current shift patterns is

easily accessible, but historical information is less complete and reliable. At one plant night shift

workers had to complete a ‘Night Worker’s Health Assessment Form’ and this would be stored with

their health records.

Four of the five plants which responded to the postal questionnaire reported that it was possible to

identify shift patterns from records held for both current and former workers. At the fifth plant, it was

reported that shift working was not in operation until recently, and so details were not currently held

in company records.

4.4 EXPOSURE ESTIMATION

4.4.1 Rationale for information collection

During the feasibility study, information was requested on three separate aspects pertaining to

exposure estimation. These were:

y Plant and process histories: these were investigated to determine whether and how

accurately it would be possible to identify different technological eras of production at the

plants as described in section 3.2.3. Information sought in this area included documented

timelines of changes in plant development and expansion/contraction, information on changes

in technology used and information on the purchase and use of different types of production

equipment.

y Chemical records: plants were asked if they had documented records of what chemicals were

used at the plant currently and in the past. This was to determine the range of potential

exposures in the industry and whether records exist that document which chemicals had been

used in which time periods. Specific questions were asked regarding the use of the key agents

listed in section 3.2.3 – arsenic compounds, chromium compounds, antimony compounds and

ionising radiation.

y Occupational hygiene monitoring and control measures: information was also collected on

occupational hygiene sampling carried out to investigate the possibilities for quantifying

exposures to different chemicals. Information was also collected on ventilation and gas

detection system records and on the use of Respiratory Protective equipment (RPE) and other

Personal Protective Equipment (PPE) within the plants.

Each of these aspects is described in more detail in the following sections.

19

4.4.2 Historical information on plant and processes

All of the plants visited were able to provide overview site histories, which documented process

changes, fab area installations and changes, and production changes over time. For some of the sites

exact dates were given for major historical changes, other plants documented changes by decade.

These timelines would enable the categorisation of periods of time in technology eras as described

previously. Changes in processes used were often included in the timelines of the site histories or

were available from other company records. At one site, details of process changes were available for

only the last 5 years, and at another site, although there were no records detailing these changes, it

was believed that they could be reconstructed from knowledge of long-serving employees. All plants

noted that there had been an increase in automation over the years.

At six of the eight plants, there were plant layouts available for the fab areas. At one of these plants

the layouts were stored in archives and may be difficult to access. Plant layouts were generally

available for the current fab areas, with little or no documentation of plant layouts from previous

years. At two sites documented layouts went back to 1996.

Five of the plants held records of equipment purchases over time. Two plants were unable to supply

this information although anecdotal knowledge of equipment installation was available. The

remaining plant had maintained the same equipment for the past 18-20 years. Information on

equipment was held in asset registers, equipment inventories, purchasing orders and product control

groups.

Information from the postal questionnaires indicated that three of the five respondents had a written

history for their company at the present site, but none had any histories of previous companies at the

same site. Four of the companies reported that, since the plant opened, there had been no significant

changes in the wafer fab processes carried out. At the fifth plant, a list of process changes was

provided although no dates could be determined for when these changes took place.

4.4.3 Chemical records

All companies held details of the chemical substances currently used on site, and it was noted that

these were generally representative of the chemicals used historically, with few changes over time. In

most plants the chemicals records identified the areas of work in which the chemicals were used, but

in at least one plant this information was not available. During the current study, plants were asked

specifically about potential exposures to arsenic compounds, chromium compounds, antimony

compounds and ionising radiation. In addition, plants were asked about other potential exposures in

their workplace and about the records held on all chemicals.

All of the plants visited had used arsenic compounds at some time in their history. Six plants

currently use gaseous or solid sources of arsenic, typically as a dopant in the ion implanter. One of

these companies has used arsenic only in the last three years. One company ceased using arsenic in

2002.

There was little evidence of the use of chromium compounds in the plants visited. Two plants used

chromium historically, one of which ceased use in 2002 (no information was available for time period

of use at the second plant). None of the other plants used chromium in wafer fabrication. Three

plants used small amounts in Quality Assurance during failure analysis testing, and one plant thought

that some chromium may have been used in the plating department although they were unable to

confirm this.

Only one of the plants used antimony compounds for wafer fabrication. At this plant, antimony

compounds were introduced three years ago and are currently used in two ion implanters. One of the

other seven plants had carried out a small feasibility study into the use of antimony but had not used it

20

any further and another plant had used small amounts of antimony as part of a developmental activity

which has now closed down.

Ionising radiation is present at all eight sites, in ion implanters in seven plants and in an x-ray process

to determine the plane of silicon crystals at the remaining site.

None of the five plants responding to the postal questionnaire reported using chromium or antimony

compounds. One plant reported using arsenic compounds. Three of the plants held records of all

chemicals used currently. Two of the five plants reported use of radiation sources in ion implanters.

Other substances used at the plants currently or historically included sulphuric acid, hydrogen

peroxide, ammonia, hydrochloric acid, gaseous sources of boron trifluoride and phosphorous, glycol

ethers, ethyl lactate, boron trichloride, silicon tetrachloride and mercury.

4.4.4 Occupational hygiene monitoring and control measures

Very limited amounts of personal or static air monitoring has taken place in the semiconductor

industry. Three of the plants visited held monitoring records from 1997 or 1998 for annual or bi­

annual air monitoring exercises. The other plants carried out limited or no air monitoring. Most of

the plants carried out occasional swab sampling for arsenic contamination on surfaces. Records of

risk assessments carried out for the Control of Substances Hazardous to Health (COSHH) scheme

were retained according to legal requirements.

Six of the eight plants held records of accident or incidents on the site. These were maintained for

various lengths of time, at one plant going back to 1952 and at another being held for the past 5 years.

Information on accident/incident reports was not available from the other two plants.

Exposures were well controlled at all the plants visited. All of the plants had continuous gas detection

systems which triggered alarms at specified exposure levels. Most plants retained records of these

alarms covering from 1 year to 10 years previously. Local exhaust ventilation systems are also

continuously monitored. Information on radiation sources takes the form of regular maintenance

checks and records are kept often for 10 years or more.

Because exposures are generally low and well controlled there are relatively few workers who ever

have to wear RPE or PPE. These individuals can be identified from training records at seven of the

eight sites visited. The shortest length of time that these are available for is 2 years, rising to over 30

years at one plant.

Among the respondents to the postal questionnaire, all four plants reported carrying out personal and

static sampling and one plant reported carrying out swab sampling of surfaces in the plant. This had

been done principally in recent years. At one plant personal and static sampling was reported to be

carried out every 1-2 years. All four plants held records of RPE training and maintenance, from 1997,

2000 and 2002 in three plants (no time period was reported for the fourth plant). Two of the plants

held records of PPE use. All four plants carried out local ventilation system monitoring and gas

detection system monitoring with records held for the same time periods as for the RPE training

records.

21

22

5 IMPLICATIONS FOR FURTHER STUDY

5.1 INTRODUCTION

Here, we summarise our findings, and these are discussed in the context of a potential GB-wide

retrospective cohort study of workers in the semiconductor industry. The following sections describe

what information is known to exist in terms of identification of a study population, possible

categorisation of individuals by occupation or exposure and the qualitative or quantitative historical

information available at the plants which would allow the assessment of changes in types or levels of

exposure over time. Based on this information, statistical power calculations have been carried out to

assess the power of a cohort study to detect effects of different sizes under assumptions based on what

is known about the potential size of the study cohort.

The implications for further study described in this section are based on our best knowledge of the

identification records, and occupational details which currently exist for potential study participants.

However, an additional aspect of the feasibility of such a study taking place is the actual availability

of these records to any study team carrying out a cohort study. While access to records of currently

employed workers should be straightforward, there are a number of Data Protection issues to be

addressed relevant to the accessibility of records from former workers, or from plants or companies

which are no longer active in the semiconductor industry. These issues, and other potential risks to

the success of any future study, are discussed in section 5.6 below.

5.2 COHORT IDENTIFICATION

Results from this feasibility study, based on visits to eight plants and postal questionnaires from four

plants, suggest that it would be possible to identify almost 5,000 current employees (Figure 1). For all

of these individuals information suitable for enabling tracing to take place at National Registers is

readily available from computerised personnel records. In addition, and more importantly for a

historical cohort study, it is estimated that identification records are available from these plants for

approximately 13,000 former workers. These records contain the key identification data to allow

tracing to take place as for the current workers. Extraction of the relevant information for former

workers would, however, be likely to be a labour intensive and time consuming exercise. Typically,

records for more recent leavers (from the mid-1990s on) are held electronically, but records prior to

this are held in paper format. Paper records are often stored in archive rooms or in numerous filing

cabinets, and the relevant identification information would need to be extracted manually, in many

cases involving searching through bulky personnel files to identify the various pieces of information.

Records of current workers are likely to be complete for all those working at the plants, and in almost

all cases this completeness can be checked by cross-reference to computerised payroll records.

Additional checks for completeness of identification of current employees can be done through cross­

checks with health and training records at most plants and with pension records at around half of the

plants.

For most companies, records of former workers were reported to be complete for all workers who had

ever been employed by the company. In some instances, however, older records of former workers

were no longer available and in at least one company, leavers records were retained only for 10 years

after date of leaving. In addition, where sites had been owned by more than one company over the

years, almost invariably records were unavailable for former workers who had never worked for the

current company. Overall, in any cohort study, there would inevitably be some incompleteness in the

identification of a population of former workers, and this would be focused primarily on those who

had worked in the industry in its early days, a group of high interest in any cohort study.

23

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24

Limited assessment of the completeness of the population of former workers would be

possible from sources such as health, training and pension records. Health records are the

most likely to have been retained for reasonable lengths of time although most companies

were unsure how far back these dated and one company reported that they were available only

for the past 3 to 4 years. Training records are typically kept for shorter periods (often 3 to 10

years) and, as mentioned above, pension records are available only sporadically. It is unlikely

that any formal quantification of cohort completeness will be available for this group.

It is possible that an investigation of any respiratory health effects in a cohort study would

include an analysis by smoking habit. Complete smoking information was available from

health records for two plants covering less than half of the identified cohort (1800 current

workers and 6000 leavers) with information available since the early to mid 1990s for a

further two plants, and available sporadically for two other plants. Analyses taking account of

smoking habit would therefore be based on a cohort of not more than 10,000 workers.

These cohort estimates are based solely on the information obtained from the 13 plants which

participated in the feasibility study. Inclusion of additional plants in any cohort study would

clearly add to the number of individuals available, so that the estimates given here are

conservative. By design, however, these additional plants tend to be those which employ

fewer workers or which have been formed relatively recently so they would be unlikely to add

greatly to the statistical power of the study.

5.3 JOB INFORMATION

Information on individual’s occupations was held primarily in personnel records. For all

identifiable cohort members, total length of employment at the plant could be extracted from

these records. For over 12,000 of the potential18,000 cohort members records exist which

allow the categorisation of each individual according to whether they had ever (or never)

worked in the fab area. These 12,000 workers include all current workers and a subset of the

former workers (Figure 1). The length of time spent working in fab areas and the calendar

periods in which this took place would also be available for the vast majority of these

workers. However, in the many cases where this information is available only in paper

records, these occupational histories would need to be reconstructed from a series of letters,

promotions, changes in pay scale, changes in clock number which would be found among all

the documents stored in the personnel files. It is likely therefore that the categorisation would

differ in reliability between plants and between more recent and older occupational records.

For the remaining former workers, those who have worked at the companies more recently

(from around the mid-1990s) could also be classified as ever/never worked in the fab area.

However, those who worked in the factory in earlier years would have partial (recent jobs

only) or no information sufficient to allocate them into these categories. As above, what

information there exists would have to be extracted in many cases from paper personnel

records.

In some plants information is available on what jobs or tasks individuals undertook within the

fab area. This information was not consistently available across the participating plants and

such detail could only be extracted for a small subset of the population. Even at those plants

where such detail was recorded, there were differences in the level of information available at

the different plants. Time spent in the fab area (length of time and calendar period) would

therefore be the most detailed occupational variable available for the majority of the study

cohort.

25

Some limited additional information on individual’s occupations was available at most plants.

This could include records of training carried out for use of specific pieces of equipment,

recording of current job at pre-employment medicals, health surveillance records for specific

exposure risks and records on whether the individual had ever been trained to use respiratory

or personal protective equipment. These sources could be used to verify and augment the

personnel records on individuals occupations, in particular to cross-check the allocation to the

ever/never fab groups for the subset of individuals for whom such supplementary information

was available.

Contract workers were also identified as being of particular interest in a study cohort.

Contract workers were used by most companies – primarily as cleaners, catering and security.

Only in a few plants were contract workers employed in the fab area, usually as cleaners,

while one company employed contract process operators. None of the plants held

comprehensive identification information for contract workers, although some names could

be extracted from security or clocking in records. It is unlikely that enough information on

contract workers exists to allow them to be included in any cohort study.

5.4 EXPOSURE INFORMATION

As noted above, individuals occupational histories could be categorised according to:

x length of time (and calendar period) employed by the company;

x whether or not they had ever worked in the fab area;

x length of time (and calendar period) worked in the fab area.

Historical and occupational hygiene information from the plants was therefore examined to

determine how it could best be linked to this level of occupational information. This

information is primarily from the eight plants visited. Some similar information, though

necessarily less detailed, was collected in the postal questionnaire and this confirmed much of

what was found in the more detailed interviews.

All plants could provide some form of historical timeline for plant development. These

timelines typically identified the commissioning and decommissioning of fab areas and

changes and developments in production processes and products manufactured (e.g. changes

to wafer sizes). For some plants specific years were given for historical events, and others

events were listed by approximate time period. Information in these plant histories would

allow the tracking of technological eras of semiconductor production similar to those

described in section 3.2.3, for all of the plants. At more than half of the plants this tracking

could be done more systematically, using purchase records for equipment, detailed plant

histories etc. At the other plants, it would be more anecdotal and only partially based on

documentation.

Detailed information on the chemicals currently used is held at all plants, and it is understood

that these have changed very little over time. Only a subset of the plants were able to

determine where in the plant each chemical had been used. All plants were able to provide

information on whether or not arsenic, chromium or antimony compounds had ever been used

(and usually the time periods during which this had taken place). Although, previously

substances including antimony trioxide, arsenic and arsenical compounds including arsine,

asbestos, chromium trioxide and chromic acid had been identified as used in the industry, in

the current study only the use of arsenic compounds was widespread. Information on use of

ionising radiation was also readily available, although it is likely that only limited numbers of

workers will have been exposed.

26

Limited amounts of personal or static air sampling took place in the plants, often as annual or

one-off monitoring exercises. Some swab sampling for arsenic also took place. Typically

results of this monitoring were available only for recent years. It was reported that levels

were generally very low, and exposure of workers well controlled. Because of this very few

workers needed to use RPE or other PPE, and where this occurred records of training or use

of the equipment is documented, again for recent years. This would allow the identification

of some members of the cohort who have worked (recently) in jobs with some potential

exposures. It is not possible to quantify exposure levels to any chemicals across time with

any reliability, except to note that exposures are reported to have been very low.

Accident and incident reports were kept by more than half of the plants and these could

provide information on any specific occurrences of potential exposures. Similarly records are

often kept of alarms triggered by continuous gas detection systems and monitoring of local

exhaust ventilation. Trigger levels of exposure, details kept of incidents and length of time

that reports were retained varied considerably among plants.

In summary, it should be possible for the majority of the study cohort, to link individual

occupational histories at the level of time and calendar periods spent working in the fab area,

to approximate technology eras at each plant. This information could then be compared with

whether or not arsenic, chromium or antimony compounds were being used during these time

periods, although only arsenic has been used in most plants. Information would be available

on what other chemicals were likely to be being used in the plant (based on current data only)

but without necessarily knowing whether these chemicals were being used in the fab and/or

non-fab areas.

5.5 STATISTICAL POWER CALCULATIONS

A detailed calculation of the power to detect an increase in mortality in a cohort study will

depend on a number of assumptions, including the baseline pattern of deaths; this will depend

in turn on the baseline rates for the causes of interest, and on the age structure of the

population under study.

In the present situation, while published mortality statistics in the form of age-specific rates

(hazard rates) are available for a number of causes of interest, we do not have data to describe

the age distribution of the target workforce. Thus, any calculations have to be based on even

more assumptions than would otherwise be the case.

Based on the summary provided in Figure 1, we estimate that there is a potential study cohort,

for whom we have information on fab/non-fab work experience, of 12,000 workers : 5950 fab

workers and 6050 non-fab workers. As noted in section 4.2.3, for the purposes of calculating

statistical power of a cohort study, we assume that 5% of these records refer to duplicate

entries primarily for workers who left the industry and subsequently rejoined and were given

a new personnel record. This leaves a cohort of 5653 fab workers and 5747 non-fab workers.

We present here some very approximate and idealised power calculations for this cohort,

based on the following simplifications:

1. A cohort of 5653 fab workers and 5747 non-fab workers

2. An equal split between the sexes

3. An average follow up of 15 years from recruitment into the cohort.

We present power calculations for a relatively common cancer (lung cancer) and for a rare

cancer (bladder cancer) to provide examples of the statistical power of a cohort study to detect

excesses of both frequent and rare causes of death.

27

If we assume that the majority of a working population are between the ages of 15 and 65,

then the average age of the workforce may be around 40 years at start of follow-up, and 55

years at the end of study. We know that death rates for most common causes rise

exponentially with age, and we may reasonably allow for both the ageing of the population

and the age distribution by taking as an average rate that for 55 years old; those rates, for lung

cancer and for all other cancers, have been extracted from published statistics for England and

Wales, 1999. These rates may produce some overestimate in the total rates for the

semiconductor industry, but should be at least about the right order of magnitude.

Lung Cancer

The annual mortality rates for 55-year-olds from lung cancer, averaged between males and

females, is around 45 per 100,000. Over a fifteen year follow-up, this would produce an

overall rate of 675 per 100,000. If that rate were observed in the non-fab population, then the

power to detect a relative risk of 1.5 in the fab workers population is calculated as 50%. The

graph below shows the power calculated for a range of possible relative risks, and we may

note that we would have 80% power of detecting a RR of about 1.8.

0

0.2

0.4

0.6

0.8

1

1.0 1.5 2.0 2.5 3.0

Odds ratio

Bladder cancer

Applying the same logic to bladder cancer, we observe that the 1999 mortality statistics for

England and Wales show a rate for both males and females of around 4 per 100,000. Over 15

years, this becomes 60 per 100,000.

At that rate, the power calculations for 5653 fab workers compared to 5747 non-fab workers

yield a power of 9% of detecting a 50% increase in risk. Power values for other values of

relative risk may be read from the graph below.

0

0.2

0.4

0.6

0.8

1

1.0 1.5 2.0 2.5 3.0

Odds ratio

28

5.6 RISKS TO CARRYING OUT FURTHER STUDY

5.6.1 Overview of potential risks

The current investigation has shown that it would be feasible to carry out a cohort study of

semiconductor plants across Great Britain. However, there remain some potential risks to the

success of such a study which should be considered further before such a study is undertaken.

The principal potential risks to a study are listed below, with more detail on the data

protection issues in particular given in section 5.6.2:

x Data protection issues – whether it will be possible to gain access to the required

information: from companies, from archives under the Data Protection Act;

x Extraction of information, particularly occupational data, from paper files is likely to

be a time-consuming and costly task to undertake;

x It is possible that the level of detail and completeness of information stored will differ

between plants and between calendar time periods within plants. In particular there

may be marked differences in the reconstruction of job information, particularly from

paper records;

x The lack of full information on smoking habits for the potential cohort, will make

interpretation of results for respiratory causes more difficult.

5.6.2 Data protection issues

In assessing the feasibility of carrying out a full-scale cohort study, it is necessary to address

issues of data protection. Several of the plants that were visited during the feasibility study

expressed concern about data protection issues associated with extracting information from

personal records. The current position on this, under Data Protection legislation, is not clear.

It is likely that collation of information on current workers would be straightforward, but

gaining access to information on workers who had previously worked at the company may be

more complex. Records for workers from previous companies, who left employment before

the current site owners took over, remain the property of the previous company. Some of

these records are held at other semiconductor premises owned by the company, while others

are held in central archives. The accessibility of these records would have to be assessed

before any full study commenced.

Another issue to consider is the tracing of mortality and cancer registration events for research

studies through the National Health Service Central Register (NHSCR), as arranged through

the Office of National Statistics (ONS) for England and Wales, or through the General

Register Office (GRO) for studies where the population is primarily Scottish. Because of

changes in legislation on data protection and confidentiality in England and Wales, ONS has

introduced a new system for the approval of studies where individual signed consent for

participation from each member of the study cohort is not available to the study team. It is

likely that any proposed cohort study would have to gain Section 60 approval through the

Patient Information Advisory Group or through the ONS in-house advisory group before

tracing could be put in place.

5.7 COMPARISON WITH USA FEASIBILITY STUDY FINDINGS

In response to the recommendations made by Cullen et al (2001) concerning the need to

conduct a retrospective epidemiology study to evaluate potential cancer risks to

semiconductor workers, the SIA contracted with the Johns Hopkins University (JHU)

Bloomberg School of Public Health to conduct a feasibility study, which reviewed the

29

availability of historical records, including employment records, job descriptions, industrial

hygiene, manufacturing processes and equipment, and employee health, within the industry

(Matanoski et al, 2004).

Basing their findings on nine participating companies, the researchers reported that sufficient

records do exist to conduct a scientifically valid epidemiology study. The US study findings

have a number of similarities to the British feasibility study. For example, the US researchers

noted that for many companies, sources of data requested were often not complete or

continuous throughout the history of the company / facility, with fabs with the earliest start

dates not being well represented in the available personnel or process records. The

acquisition and divestiture of fabs by the participating companies was also noted to pose

particular challenges for a subsequent epidemiology study. Firstly it was noted that there may

be difficulty in reconstructing the start and closing dates of fabs as little information is

transferred onto new owners. Historical information on the products manufactured was

readily available for half of the companies visited, with the detail and completeness of

production records diminishing with time. Secondly, in the case of acquisitions, generally

only the personnel records of current employees are transferred to the new company, with

records of leavers being retained by the original owner. It was also noted that most

companies changing from one computerised software system to the next, terminated

individuals were often not carried forward into the new system, with histories of active

employees usually being truncated. Matanoski et al (2004) also discuss issues surrounding

the transfer of workers during new company ownership and how workers may either carry

risks associated with their previous exposures into new production, or that they can be

healthier than others exposed to the older technology because they ‘survived’ and are still

employed. It was also noted that records relating to former operations and other potential

exposure measures tended to remain with the facility and new owner though this was not

always the case in the British study.

About 66% of companies queried about past smoking habits at least asked the question of

whether the individual ever/never smoked, usually during a pre-employment medical

examination. In the British study, smoking information is available for 83% of the plants

however in the majority of instances such information is incomplete and has only been

routinely held since the early 1990s onwards. Companies were found to have a unique set of

records for fab workers that identify each individual who is trained to work in a specific area

of the clean room or operate specific tools. It is not noted whether these records are available

for the whole lifespan of the fab however the researchers do mention that these records are

usually hard copy and access to such data may involve searching different sources. Indeed in

the British study, training records were only normally available from the mid 1990s onwards

and again it was difficult in some instances to determine their exact location or completeness.

Whereas companies were able to provide further detail on whether an employee was a fab, or

non-fab worker and details of fab workers work location, previous work location and sub area

of employment for the various decades in the US study, this level of detail was not able to be

determined in the British study with records, on the whole, being able to categorise workers

as fab or non fab, with some companies being able to provide limited additional information

on individual’s occupations. As reported in Section 4.2.1, it was also noted by Matanoski et

al (2004) that there has been a gradual shift for both fab and non-fab workers with a reduction

in the female to male ratio of employees over time, primarily due to changing technology

needs. The amount and detail contained in industrial hygiene data was found to be variable,

with the earliest sampling taking place in the late 1970s. Monitoring also appeared to be

generally undertaken in response to problems or complaints and thus may overestimate

typical or average exposures (Matanoski et al; 2004). In the British study very limited air

monitoring had taken place and these were collected from 1997 onwards. Both studies also

acknowledge problems with fixed gas monitoring systems records, in that most of the

30

information is not routinely retained. Matanoski et al (2004) also provides an outline of

several possible designs for a proposed epidemiological study.

31

6 CONCLUSIONS

The feasibility study was based on visits to eight of the largest and longest running

semiconductor plants in Great Britain, and the collection of postal questionnaire information

from five smaller or more recently opened facilities. These have provided a comprehensive

review of the availability, completeness and quality of existing records held by the

companies. The findings of this review show that the extent of records held in the

semiconductor industry are very similar to those found in multi-centre cohort studies in other

industries.

The findings of this review show that the extent of records held in the semiconductor industry

is very similar to that found in multi-centre cohort studies in other industries. Based on our

best knowledge of these records held, we conclude that it would be feasible to carry out a

cohort study of semiconductor plants across Britain. When considering a possible design for

a future study a number of issues must be considered and addressed.

Firstly, the population must be representative of the total industry and the companies

represented. The results of the feasibility study show that identification information is

available for around 18,000 or more current and former employees. Identification of workers

would principally be from personnel records, with other records such as payroll, health and

training records being available which would allow at least limited checking of the

completeness of the personnel cohorts. However, many of the records, in particular for those

who left the industry prior to the early to mid 1990s, may be difficult to access and the

extraction of the relevant identification data from paper records is likely to be a time

consuming task. In addition, some of the older personnel records, for plants which have

subsequently been taken over by a new company, are held in central archives of the original

company. It is not known if these records would be made available to researchers.

Analysis of the health of these workers in relation to occupation would be possible only for

broad groupings of individuals who had ever/never worked in the fab area. No further

detailed information on job within the fab area or potential exposures to specific chemicals is

consistently available across companies or across time periods within companies. However, it

should be possible for the majority of the study cohort, to link individual occupational

histories at the level of time and calendar periods spent working in the fab area, to

approximate technology eras at each plant. This information could then be compared with

whether or not particular chemicals of interest such as arsenic, were being used during these

time periods. Contractors who worked in the industry - often maintenance, security, catering

or cleaning staff - cannot be systematically identified from existing records. It is therefore

unlikely that enough information on contract workers exists to allow them to be included in

any cohort study. As with the identification information, the accessibility and quality of the

retained records varies over time, with older records more likely to be less detailed and to be

held in paper files. As before, extraction of this information, specifically the reconstruction of

occupational histories of each individual’s jobs within the industry, would not be

straightforward, and would best be carried out by someone experienced with work in the

company concerned, for example a retired manager or other senior employee. Smoking

information would be available for a subset of the study group at most around half of those

identified and was only routinely held from early 1990 onwards. The lack of full information

on smoking habits for the potential cohort will make interpretation of results for respiratory

causes more difficult.

Whilst the majority of the information is available from some of the largest and longest

running semiconductor plants in the UK, thus representing a wide variety of the population

33

groups, it is possible that populations from the early years of employment in some companies

may be missed. To make the population representative, the study must at least be able to

identify the complete cohort of workers employed by a company from the beginning of their

ownership to be sure that data from early years are similar for companies providing data

throughout their operation compared to those with missing data. Our findings suggest that it

is indeed possible to identify a cohort for all present site owners surveyed. The study

population also needs to be of sufficient length in follow up to test for the potential risk

cancers in question. Although detail was not obtained on the breakdown of population

numbers for various time periods, despite companies starting manufacturing at the earliest in

the 1940/50’s, due to changes in company ownership, records are only routinely held from the

mid 1980’s onwards. Access to central archives of the original site owners would not only

increase the size and representative ness of the cohort but would also increase the population

of employees with sufficient duration of follow up to expect to demonstrate a risk, thus

increasing the validity of the design of any future study.

Therefore a major consideration in the feasibility and planning of any future study is the

accessibility of all of these records to researchers. It is not yet clear whether, under the Data

Protection Act, researchers would be able to access records of former workers held either at

the company concerned or in central documents archives, for the purposes of a health or other

epidemiological study and this must be resolved before any further study could commence.

Power values measure the probability that the study will be able to detect a significant risk at

a specific level of increased risk between different groups. Many factors affect power, such

as the size of the study population, however the statistical power calculations show that a

study of a cohort of this size should have reasonable statistical power to detect an excess risk

compared with standard reference rates in a common cause of death (80% power to detect a

relative risk of around 1.8), although relatively poor statistical power to detect excesses in

rarer causes.

We therefore conclude that, provided access to the data records can be agreed with the

companies and with Data Protection custodians, it would be feasible:

1. to construct a study of a reasonably representative cohort of workers from the UK

semiconductor industry;

2. to trace their mortality and/or cancer incidence within UK national systems;

3. to carry out analyses comparing the mortality or cancer incidence within the cohort

with standard national or regional age- and sex-specific mortality rates for chosen

causes;

4. to carry out analyses making comparisons internal to the cohort, distinguishing work

experience in the fab/non-fab areas, and further distinguishing these by calendar

periods representing the presence of different hazards;

5. to carry out only limited analyses that adjusted for the strong effects of smoking on

certain risks.

34

7 REFERENCES

Cullen MR, Checkoway H, Eisen EA, Kelsey K, Rice C, Wegman DH, Whitehead L (2001).

Cancer risk among wafer fabrication workers in the semiconductor industry. Executive

Summary. University of Massachusetts, Lowell.

http://www.sia-online.org/downloads/SAC_Summary.pdf

Health and Safety Executive (2002). Inspections by the Health and Safety Executive in 2002

of manufacturers of semiconductors in Great Britain.

www.hse.gov.uk/fod/eng-util/semicon.pdf

Matanoski GM, Lees PSJ, Tao X, Lantry DA (2004). Report on SIA worker health feasibility

study (SIA scoping study). John Hopkins University, Bloomberg School of Public Health.

www.sia-online.org/downloads/WHP_JHU_Final_Report.pdf

McElvenny DM, Darnton AJ, Hodgson JT, Clarke SD, Elliott RC, Osman J (2003).

Investigation of cancer incidence and mortality at a Scottish semiconductor manufacturing

facility. Occupational Medicine Oct;53(7):419-30.

Nichols L, Sorahan T (2004). Further update of cancer incidence and cancer mortality in a

cohort of semiconductor workers. HSE Research Report 265.

www.hse.gov.uk/research/rrpdf/rr265.pdf

35

36

8 ACKNOWLEDGEMENTS

This study was funded by the Health and Safety Executive. We thank the management and

workers at the eight plants visited by the study team for their cooperation and willingness to

supply the information necessary for this feasibility study, and the plants which participated in

the postal questionnaire survey. We are grateful to Derek Boyd of NMI for his assistance in

communications with the plants. We thank the members of the Scientific Advisory Group –

Professor David Forman, Dr John Osman, Mr Nick Jolly, Dr Adele Pilkington, Professor

Alastair Hay and Mr Damien McElvenny – for their help, encouragement and advice during

the study.

37

38

Appendix 1: Pro-forma for plant visits

39

40

SEMICONDUCTOR FEASIBILITY STUDY

Protocol for company visits

1. BACKGROUND

A feasibility study is being carried out by the Institute of Occupational Medicine (IOM) and the

London School of Hygiene and Tropical Medicine (LSHTM) to establish whether there is sufficient

information on past and present employees to provide a cohort that is large enough for an informative

investigation of cancer in the workers in the industry. To do this, members of the study team are

visiting up to 12 currently operating companies to investigate the availability and completeness of

their company records.

2. PLANT VISITS

Who? Each visit will be carried out by two members of the research study team, an epidemiologist

(either Hilary Cowie, IOM or Mike Ahern, LSHTM) and an occupational hygienist (Karen Creely,

IOM).

When? Most company visits will take place during August and September 2004.

How long will they take? Each visit should take no more than one working day.

What is the purpose of the visits: The purpose of the visits to the factories is to determine which data

items are available in the factory records and for which workers. In particular we need to investigate

the availability and completeness of the factory records with respect to identification data,

occupational history data, smoking data and information about what chemicals workers have been

exposed to; we also need to find out how the records are held and how, if a study went ahead, the

required data could be extracted from them.

What will the visit entail? During each visit, the researchers, either together or separately, would like

to speak to staff from the personnel or records department, who have knowledge of what records are

held for each worker and past worker, and where and how they are stored, and to staff from the

fabrication plant who have knowledge on the historical development of the processes since the plant

opened and the various chemicals used. The researchers would like to see examples of the kinds of

records kept, and to have a brief tour of the fabrication plant. The following sections describe in more

detail the information required.

3. AVAILABILITY AND COMPLETENESS OF DATA ON INDIVIDUAL WORKERS

3.1 Availability and completeness of employment records

x What record systems are there that might help researchers assemble a file of

identification details present and past workers, and their work histories at the

company?

x For each system, what is the earliest date for which records are available?

x Are records held for both current workers and leavers?

41

x How complete are the records between their start date and the present (for current

workers and for leavers)? [for example, is there a period during which records or

leavers were discarded, or are records discarded if workers worked only a short

duration?]

x Do records include only full-time workers (or both full and part-time workers)? If

they include part-time workers, can they be identified easily?

x Do records include only permanent workers (or both permanent and temporary

workers)? If they include temporary workers can they be identified easily?

x If the company has been the subject of a takeover, what records are available from the

previous owner, and where are they stored?

x Are there records help by the company for plants that are now closed (eg, as a result

of a take-over)

x What ID data are held for each worker (for current workers, for leavers)? We are

particularly interested in Full Name, sex, and date of birth; also useful are NI/NHS

number, and maiden name (if name has changed).

x Are there any records of contract workers? (eg cleaners, construction workers,

periodic maintenance workers)

3.2 Availability and completeness of occupational histories

x Are any data held specifying the department or the occupation of each worker

(occupational data)?

x Are the available occupational data held for everyone identified in 3.1 above? If not,

who is it held for - eg. over specific time periods, for specific occupations, for those

joining after a specific date?

x What occupational data are held - date of starting to work at this plant, date of

leaving, job at joining, job at leaving, job changes in the intervening period (with

dates, all job changes or only major job changes such as change of process, change

of payscale etc)?

x Are any shift pattern, night working and overtime data held in factory records?

x Are any available shift pattern/ night working and overtime data held for everyone

identified in 3.1? If not, who are they held for – eg. over specific time periods, for

specific occupations, for those joining after a specific date?

x At what levels of detail are jobs distinguished in the occupational histories? (eg

departmental code, occupation code, if so how many categories; if not is there a

verbal description; is it possible to distinguish workers likely to be most exposed ?)

x Is the quality of occupational data the same for all individuals? If not, does it differ

by time period, by current/leaver status, by job?

42

3.3 Availability and completeness of smoking information

x Are any smoking data held in factory or medical records?

x Are any available smoking data held for everyone identified in 3.1 above? If not,

who is it held for - eg. over specific time periods, for specific occupations, for those

joining after a specific date?

x What smoking data are held? Are they sufficient to classify each individual as a

lifelong non-smoker or a smoker (current or ex)?

3.4 Accessibility of data

x Are the records stored in ledgers, record cards, computer (or combination of these)?

x How are they sorted?

x Are they all in one place (or current and leaver stored separately)?

4. AVAILABILITY OF INFORMATION ON EXPOSURES

4.1 Historical development of the plant

x When did semi-conductor / wafer production commence?

x What information is held – layout, number and size of buildings, processes employed

and where, plans of factory available, technology used, number of staff, quantity and

type of ventilation, raw materials used and products produced?

x What changes have there been to the processes and plant over time?

x What information is held – changes in clean room technology and processes,

expansion / reduction of processes, dates of when fabrication area was reorganised

or when ventilation systems were upgraded, changes in production areas, changes in

methods of production and tasks involved, plans of factory layout, purchase records,

production records, engineering reports, photographs, cleaning / maintenance

records?

x At what level of detail is the recording of the historical development of the plant

held?

x What additional information on the above can be obtained from interviewing long-

serving personnel?

4.2 Exposure information

x Are any chemical substance data held in factory records?

x What chemical substance data are held – types and quantities of chemicals used,

dates of use, processes and tasks used, details of accidents / incidents, quantities of

finished materials produced?

x At what level of detail is the recording of chemical use at the plant held?

43

x Are any monitoring data held in factory records and how are these stored?

x What monitoring data are held – date started, personal / static / continuous,

substances measured, processes and occupations covered, over specific time periods,

numbers of measurements, purpose of sampling, control measures in place?

x Are any ionising and non-ionising radiation data held in the factory records?

x What ionising and non-ionising radiation data are held - date started, processes and

occupations covered, over specific time periods, numbers of measurements?

x Are any data held in factory records on the following key chemicals – arsenic

compounds, chromium compounds and antimony compounds?

x What data are held (about what?) – areas and processes used, (cross check with

monitoring data) raw materials used and changes over time (purchase orders), waste

disposal records?

x What additional information can be obtained from interviewing long-serving

personnel?

4.3 Control measures

x Are any respirator and personal protective equipment use data held?

x What data is held - date of introduction, areas /situation used, types of equipment

used, changes in equipment used and when, maintenance and replacement schedules,

training records?

x Are any process control data held?

x What data is held – areas and processes controls present, type of controls present and

when, maintenance records, assessment records, dates controls used, factory plans?

x What additional information can be obtained from interviewing long-serving

personnel?

44

Appendix 2 : Questionnaires for small and closed plants

45

46

SEMICONDUCTORS FEASIBILITY STUDY

INTRODUCTION

In 2001 the Health and Safety Executive (HSE) reported on a study of cancer risk at a semiconductor plant in

Greenock, Scotland. The number of people in the study was relatively small, and the report was therefore unable

to provide clear answers on possible risks for any cancers. The HSE and the Department of Trade and Industry

(DTI) have jointly funded and commissioned a new feasibility study. The aim of this study is to establish whether

a full-scale study among workers in the British semiconductor industry would be possible and useful. The

semiconductor industry is supportive of this feasibility study.

The Institute of Occupational Medicine (IOM) and the London School of Hygiene and Tropical Medicine have

been asked to find out whether existing semiconductor factories records can tell us who has worked in the

industry, for what time periods, and how working conditions and chemical exposures have changed over time.

This questionnaire is being sent to representative factories within the UK to obtain details on the availability and

completeness of data held by factories on employee identification and occupational history, employees smoking

history, chemical information as well as information on plant and wafer fabrication process history. This

questionnaire should be completed by the person(s) in your organisation with responsibilities in these areas. We

would be grateful if you would take the time to fill in the questionnaire. Once you have completed the

questionnaire, please return it to the IOM in the reply-paid envelope provided to reach us as soon as possible.

All information you provide will only be used for research purposes. No names or identifying information

will be published.

INSTRUCTIONS

1. For most of the questions there is a list of possible answers with a box printed beside each one. Please

choose your answer by putting a tick in the box ; beside your chosen response. In some cases you

may be required to tick more than one box, in which case you will be asked ‘Please tick ALL that apply’.

2. There are spaces in some questions for you to write your answer or to give more details about your

chosen response.

3. Some responses are followed by instructions, which allow you to miss out certain questions. If you have

chosen such a response, you should go forward to the question indicated.

4. If you are unsure of the answer to any question, please leave it blank.

5. If you have any further relevant information that you would like to include, please use the space

provided on the back page of the questionnaire.

47

SECTION A: SITE HISTORY

1. a. In what year did manufacturing of silicon wafer fabrication first take place on

this site (under the current or a previous company)?

b. In what year did manufacturing of Gallium Arsenide wafer fabrication first take

place on this site (under the current or a previous company)?

2. Please give details, in the table provided below, of all the semiconductor companies which

have manufactured wafers on this site, with dates of operation.

Company names Date of operation

3. Is there a written history (e.g. in the staff handbook, company report) for any of the

following

a. of this company at this site

b. of previous companies at this site

Yes No

4. Since the plant opened, have there been any significant changes in the wafer fab Yes No

processes carried out (e.g. progression away from wet bench methods, greater

process automation and enclosure)?

If NO, please go to question 6

If YES, please give brief details below and dates of changes

48

5. If you answered YES to Q4, are any written records of these changes held

(e.g. site plans, equipment purchase etc)?

If YES, please give brief details below and associated dates.

SECTION B: INFORMATION ON CURRENT WORKERS

6. Approximately, how many people are currently employed at this site?

7. Do you know approximately how many of the current workers have worked at the

this site since it opened?

Yes No Don’t know

If YES, please give the approximate number of current workers.

8. Please give details, in the table provided below, of the approximate numbers of people (not

including sub-contractors) who currently work in each of the following areas at this site:

Area of work Approximate number of people

Fab

Non fab related production areas

Maintenance (non fab areas)

Maintenance (fab areas)

Management/office staff

49

9. Which of the following personal details are held for current workers in site records? Yes No

a. Full name

b. Maiden name (where applicable)

c. Sex

d. Date of birth

e. National Insurance (NI) number

f. National Health Service (NHS) number

g. Address

h. Length of service

i. Other (please give details below)

10. How are these personal details recorded? (Please tick the answer that is MOST applicable)

a. paper only

b. computer only

c. paper and computer

d. do not know

11. What information on occupation is held in these records? Please give details below (e.g.

department, job title, changes in job)

50

12. From these occupational records is it possible to identify: Yes No Don’t know

a. fab/non-fab workers

b. jobs held within the fab area for each fab worker

c. maintenance workers

13. Is it possible to identify individual worker’s shift patterns from these records? Yes No Don’t know

SECTION C: INFORMATION ON LEAVERS

14. Does your company retain records on leavers? Yes No

If YES, please give details below of how long these records are retained (e.g. for 10 years

after leaving, or from March 1987 – February 1993)

15. Approximately how many leavers’ records are available?

16. Which of the following personal details are held for leavers in site records?

a. Full name

b. Maiden name (where applicable)

c. Sex

d. Date of birth

e. NI number

f. NHS number

g. Address

h. Length of service

i. Other (please give details below)

Yes No

51

17. How are these personal details recorded? (Please tick the answer that is MOST applicable)

a. paper only

b. computer only

c. paper and computer

d. do not know

18. What information on occupation is held in these records? Please give details below (e.g.

department, job title, changes in job)

19. From these occupational records is it possible to identify: Yes No Don’t know

a. fab/non-fab workers

b. jobs held within the fab area

c. maintenance workers

20. Is it possible to identify individual worker’s shift patterns from these records? Yes No Don’t know

52

SECTION D: INFORMATION ON CONTRACT WORKERS

21. a. Do you currently employ any contract workers? Yes No

b. Have you ever employed contract workers? Yes No

If YES to (a) or (b) then please give details, in the table below, of the areas in which they work

and for what time periods

Fab Non-fab Contract company used Time period

[Date from (mm/yyyy) –

Date to (mm/yyyy)]

Cleaning

Maintenance

Security

Catering

Other

(please give details below)

Other (details):

SECTION E: OCCUPATIONAL HEALTH RECORDS

22. For what time period are occupational health records held?

mm yyyy

from:

to:

23. Are these records held for any of the following: Yes No

a. Current workers

b. Leavers

c. Contractors

If YES, please give details below of how long these records are retained after the employee

has left the company (e.g. for 10 years after leaving, or from March 1987 – February 1993).

53

24. Are pre-employment medicals carried out? Yes No

If YES, please append the questionnaires that are used, if possible.

25. Do the occupational health records hold any information on smoking habits? NoYes

If YES, for what time periods? mm yyyy

/

/

26. Has any health surveillance been carried out (e.g. urinary arsenic monitoring)? Yes No

If YES, please give details below on who was included, what surveillance was done and for

what time periods.

SECTION F: INFORMATION ON EXPOSURES

27. Please give details, in the table below, of the time periods for which any of the following

records are held.

Records Records held

(YES/NO)

Time period held

[Date from (mm/yyyy) – Date to (mm/yyyy)]

Example YES 05/1993 – 05/2003

Safety Data Sheets

Chemical purchase records

Substance approval forms

COSHH assessments

Accident/Incident records

Other (please give details)

Other (details):

54

28. Please give details, in the table below, the time periods for which any of the following

substances have been used.

Substance Substance used

(YES/NO)

Time period used

[Date from (mm/yyyy) – Date to (mm/yyyy)]

Example YES 01/1985-11/1992

Arsenic compounds

Chromium compounds

Antimony compounds

29. Do you have any records detailing the types of chemicals used by process and time periods? Yes No

If YES, please give details below

30. Have you carried out (either by in house or by outside consultants) any of the following types

of monitoring in the fab area:

Monitoring Monitoring carrie

(YES/NO)

d out Time period

[Date from (mm/yyyy) – Date to (mm/yyyy)]

Example YES 07/2001-02/2002

Personal sampling

Static sampling

Swab sampling

If YES, please give details below of substances and processes monitored.

31. Have radiation sources ever been used in the plant? Yes No

If YES, please give brief details of these sources, time periods used and the types of records

held for these time periods.

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SECTION G: INFORMATION ON CONTROL MEASURES

32. Do you keep records of any of the following?

Control measures Records kept

(YES/NO)

Time period used

[Date from (mm/yyyy) – Date to (mm/yyyy)]

Example YES 06/1988 – 03/1995

Respiratory Protective Equipment

(RPE) training

RPE maintenance / replacement

schedules

Personal Protective Equipment (PPE)

use

Local Exhaust Ventilation (LEV)

monitoring

Gas detection systems

Other (please give details)

Other (details):

SECTION H: OTHER INFORMATION

33. Are all factory records described above held on site? Yes Don’t knowNo

If NO, please give details, in the table below, of what factory records are held on site and for

what time periods.

Records held on site Time period used

[Date from (mm/yyyy) – Date to (mm/yyyy)]

56

34. If additional records are held off site, where are these additional records stored?

35. If the company has, at any stage, changed ownership, please give details below of where

records from previous owners are stored (if known)

If you have any further relevant information that you would like to include, please use the

space provided on the back page of the questionnaire.

This is the end of the questionnaire. Thank you very much for filling it in. Please

return it to the IOM in the reply-paid envelope provided to reach us as soon as

possible.

All of your responses will be treated in the strictest confidence.

If you have any questions about this study please contact Hilary Cowie at the address

below:

INSTITUTE OF OCCUPATIONAL MEDICINE Research Park North Riccarton EDINBURGH EH14 4AP Tel: 0870 850 5131 Fax: 0870 850 5132 e-mail: Hilary.Cowie@iomhq.org.uk website: www.iom-world.org

57

Additional space (if required) any further relevant information:

58

SEMICONDUCTORS FEASIBILITY STUDY

INTRODUCTION Some years ago the Health and Safety Executive (HSE) did a study to investigate whether there was any

cancer risk at a plant in Greenock, Scotland, but as this provided only a small group of people for study it

could not provide clear answers on possible risks. The HSE and the Department of Trade and Industry

(DTI) have now jointly funded and commissioned a new feasibility study. The aim of this is to find out

whether a full-scale study among workers in the British semiconductor industry would be possible and

useful. The semiconductor industry is supportive of this study taking place.

The Institute of Occupational Medicine (IOM) and the London School of Hygiene and Tropical Medicine

have been asked to find out whether existing semiconductor factory records can tell us who have worked in

the industry, and for what time periods, and how working conditions and chemical exposures have changed

over the years.

This questionnaire is being sent to representatives within the UK to obtain details on the availability and

completeness of data held for closed semiconductor factories on employee identification and occupational

history, employees smoking history, chemical information as well as information on plant and wafer

fabrication process history. This questionnaire should be completed by person(s) in your organisation with

knowledge of the company archives. We would be grateful if you would take the time to fill in the

questionnaire. Once you have completed the questionnaire, please return it to the IOM in the reply-paid

envelope provided to reach us as soon as possible.

All information you provide will only be used for research purposes. No names or identifying

information will be published.

INSTRUCTIONS

1. For most of the questions there is a list of possible answers with a box printed beside each one.

Please choose your answer by putting a tick in the box ; beside your chosen response. In some

cases you may be required to tick more than one box, in which case you will be asked ‘Please tick

ALL that apply’.

2. There are spaces in some questions for you to write your answer or to give more details about

your chosen response.

3. If you are unsure of the answer to any question, please leave it blank.

4. If you have any further relevant information that you would like to include, please use the space

provided on the back page of the questionnaire.

59

a. For what time period did manufacturing of silicon wafers

5. SECTION A: SITE HISTORY

1. Name and previous address of closed semiconductor site.

2.

Previous address:

Name of semiconductor site:

take place on this site under your company ownership from to

(years)?

c. For what time period did manufacturing of Gallium Arsenide from to

wafers take place on this site under your company ownership

(years)?

d. For what time period did manufacturing of silicon wafers take from to

place on this site (including all previous company ownerships)

(years)?

e. For what time period did manufacturing of Gallium Arsenide from to

wafers take place on this site (including all previous company

ownerships) (years)?

3. After your company left the site was it purchased by another semiconductor

manufacturing company?

If YES, please provide details of company name and date of transfer of ownership.

Don’t knowNoYes

If NO, when did semiconductor manufacturing cease at this site? year

60

y

4. If applicable, please give details, in the table provided below, of all the semiconductor companies

which have previously manufactured wafers on this site (i.e. before your company), with dates of

operation.

Company names Date of operation

5. Is there a written history available in the company archives (e.g. in the staff handbook, compan

report) for any of the following? Yes No Don’t know

a. of your company at this site

b. of previous companies at this site

6. Did your company retain records for the site’s employees? Yes No Don’t know

SECTION B: INFORMATION ON WORKERS

If YES, please give details of time period covered and details of how long and where these records

are retained

7. Approximately how many employee records are available?

61

8. Which of the following information is held for previous employees in the site records? Yes No Don’t know

a. Full name

b. Maiden name (where applicable)

c. Sex

d. Date of birth

e. National Insurance number

f. National Health Service number

g. Address

h. Length of service

i. Other (please give details below)

9. How are these identification records held?

a. paper only

b. computer only

c. paper and computer

d. don’t know

10. What information on occupation is held on these records? Please give details below (e.g.

department, job title, changes in job)

11. From these occupational records is it possible to identify? Yes No Don’t know

a. fab/non-fab workers

b. jobs held within the fab area for each fab worker

c. maintenance workers

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12. Is it possible to identify individual worker’s shift patterns from these records? Yes No Don’t know

SECTION C: INFORMATION ON CONTRACT WORKERS

13. Did the company ever employ contract workers? Yes No Don’t know

If YES, are records held detailing:

a. names of companies used

b. areas worked

c. time periods covered

SECTION D: OCCUPATIONAL HEALTH RECORDS

14. For what time period are occupational health records held?

/

/

to:

from:

15. Have occupational health records been retained for all sites previous Yes No Don’t know

employees?

16. Approximately, how many occupational health records are held?

63

17. Do the occupational health records hold any information on smoking? Yes No Don’t know

If YES, for what time periods? mm yyyy

from:

to:

18. Was any health surveillance carried out (e.g. urinary arsenic monitoring)? Yes No Don’t know

If YES, please give details below on who was included and what surveillance is done and for what

time periods.

SECTION E: INFORMATION ON EXPOSURES

19. Please give details, in the table below, of the time periods for which any of the following records are

held.

Records Records held

(YES / NO/

DON’T KNOW)

Type of records

(paper / electronic /

combination

Time period held

[Date from (mm/yyyy)

– Date to (mm/yyyy)]

Example YES Paper 11/2002-11/2004

Safety Data Sheets

Chemical purchase records

Substance approval forms

COSHH assessments

Accident/Incident records

Other (please give details)

Other (details):

64

20. Do you have any records detailing the types of chemicals used by process Yes No Don’t know

by time periods?

If YES, please give details below.

21. Are records held for any of the following types of monitoring in the fab area?

Monitoring Records held

(YES / NO /

DON’T KNOW)

Type of records

(paper / electronic /

combination)

Time period held

[Date from (mm/yyyy) –

Date to (mm/yyyy)]

Example YES Paper 11/2002-11/2004

Personal sampling

Static sampling

Swab sampling

If YES, please give details below of substances and processes monitored.

22. Have radiation sources ever been used in the plant? Yes No Don’t know

If YES, please give brief details of the types of records held for these sources and the time periods

covered.

65

SECTION F: INFORMATION ON CONTROL MEASURES

23. Have any of the following records been retained?

Control measures Records kept

(YES / NO /

DON’T KNOW)

Type of records

(paper / electronic /

combination)

Time period held

[Date from (mm/yyyy)

– Date to (mm/yyyy)]

Example YES Paper 11/2002-11/2004

Respiratory Protective Equipment (RPE)

training

RPE maintenance / replacement schedules

Local Exhaust Ventilation (LEV) monitoring

Gas detection systems records

Personal Protective Equipment (PPE) use

Other (please give details)

Other (details):

SECTION G: OTHER INFORMATION

24. Are all factory records discussed held in one central location?

If YES, please provide location details

Yes Don’t knowNo

If NO, please give details, in the table below, of what factory records are held where and for what

time periods.

Records held Location Time period held

[Date from (mm/yyyy)

– Date to (mm/yyyy)]

66

25. Are records held by previous owners still available? Yes No Don’t know

If YES, please provide location details

26. In the event of a change in semiconductor manufacturing ownership (see Q3), were company

records transferred to the new owner?

If YES, please provide details:

Records Time period

[Date from (mm/yyyy) – Date to (mm/yyyy)]

If you have any further relevant information that you would like to include, please use the

space provided on the back page of the questionnaire.

That is the end of the questionnaire. Thank you very much for filling it in. Please return it

to the IOM in the reply-paid envelope provided to reach us as soon as possible.

All of your responses will be treated in the strictest confidence.

If you have any questions about this study please contact Hilary Cowie at the address

below:

INSTITUTE OF OCCUPATIONAL MEDICINE Research Park North Riccarton EDINBURGH EH14 4AP Tel: 0870 850 5131 Fax: 0870 850 5132 e-mail: Hilary.Cowie@iomhq.org.uk website: www.iom-world.org

67

Additional space (if required) any further relevant information:

68

Appendix 3: Announcement to Workers

69

70

Semiconductor Feasibility Study – Information for Workers

Over the next few months, some factories in the British semiconductor industry will be visited

by a team of researchers. This note, from the research team, is to give you some background

about these visits.

Some years ago the Health and Safety Executive (HSE) did a study to investigate whether

there was any cancer risk at a plant at Greenock in Scotland, but as this provided only a small

group of people for study it could not provide clear answers on possible risks. The HSE and

the Department of Trade and Industry (DTI) have now jointly funded and commissioned a

new feasibility study. The aim of this is to find out whether a full-scale study among workers

in the British semiconductor industry would be possible and useful.

The new feasibility study will be carried out over about twelve months, by independent

researchers from the Institute of Occupational Medicine in Edinburgh and the London School

of Hygiene and Tropical Medicine. It will be guided by an advisory committee including

members from the funding bodies (HSE and DTI), industry and workers’ representatives.*

The semiconductor industry is supportive of this study taking place.

To find out whether a full-scale, nation-wide study is worthwhile, it will be necessary during

the feasibility study to find out whether factory records can tell us who has worked at the

factory, over a time period long enough to have shown up any relevant health problems. For

the feasibility study, the researchers will visit up to about 12 factories. These have been

selected to ensure that there are both sufficient numbers of employees and enough workers

with long periods of employment in the industry. The research team will examine factory

personnel and other records to find out what has been recorded, and will interview a small

number of management and staff to find out what is known about workplace conditions and

changes over the years.

Since this is purely a feasibility study, no data on individual workers will be extracted at this

stage. At the end of the study, the researchers will make recommendations about whether a

national study could be done, based on the information that is available.

* The workers’ representative on the advisory committee will be Alastair Hay. He works at

the University of Leeds as Professor of Environmental Toxicology. Alastair Hay has been a

Trades Union Congress (TUC) nominee on various committees in the HSE for many years.

The TUC has agreed to Alastair representing workers’ interests in the feasibility study.

Further details about the study are available on the HSE website at: www.hse.gov.uk/statistics/live/index.htm

Ex employees from the industry seeking further information should contact Derek Boyd,

Chief Executive, National Microelectronics Institute, 01506-424896, derek.boyd@nmi.org.uk

71

Printed and published by the Health and Safety Executive C1.10 09/05

ISBN 0-7176-6167-9

RR 384

78071 7 661 671£25.00 9