Feychting ELF and Breastcancer

8/13/2019 Feychting ELF and Breastcancer

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Electromagnetic fields andfemale breast cancer

Maria FeychtingInstitute of Environmental Medicine,

Karolinska Institutet


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Breast cancer incidence

Source: Socialstyrelsens statistikdatabaser, Cancer Registry

0

20

40

60

80

100

120

140

160

180

200

1970 1975 1980 1985 1990 1995 2000 2005

No./100 000

Women

Men

Year


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Background

Hypotheses Magnetic field exposure suppresses

melatonin production (Stevens RG, 1987)

Melatonin protects against breast cancerdevelopment (Cohen M, 1978)

Therefore:

Magnetic field exposure increases breast cancer riskStevens RG, 1987


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Magnetic fields - melatonin

Contradictory evidence

Most human experimental studies found no

effect

Several observational studies have found

lower melatonin levels in exposed groups Often limited to subgroups


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Melatonin breast cancer, experimental

In vivo and in vitro experimental researchsupport protective effect of melatonin Effects of melatonin treatment have been

shown on MCF-7 breast cancer cells (estrogenreceptor positive)

Reduced incidence of chemically induced breasttumors after melatonin treatment

Increased incidence of breast tumors afterpinealectomy and chemical induction of breasttumors


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Melatonin breast cancer, humans

One prospective epidemiological studyfound no association

Travis et al. JNCI 2004

Another prospective epidemiological studyfound a lower breast cancer incidence in

women with high melatonin levelsSchernhammer et al. JNCI 2005


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Evaluations of EMF-breast cancer

The literature has been reviewed byseveral national and international bodies IARC UK AGNIR

and others

Conclusions: the available evidence isinadequate for an assessment

Most recent:

WHO Environmental Health Criteria


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IARC evaluation starting point

Performed in 2001 The epidemiologic evidence indicated little

or no overall effect

Some studies suggested an effect forpremenopausal breast cancer

Especially estrogen receptor positive, ER+

Fit the hypothesized biological mechanism


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Exposure sources

Occupational exposure Residential exposure

Electric bed heating devices, e.g.electric blankets


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Occupational exposure assessment

Early studies categorized job-titles intoelectrical occupations

Later studies have made personalmeasurements in occupations mostly onmen and created Job-Exposure-Matrices

(JEM)


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Occupational exposure assessment

Measurements on men may not adequatelyestimate magnetic field exposure for women differences between men and women holding

the same occupation,

no information about the exposure in typicallyfemale occupations - large proportion of womenwith unknown exposure levels

A Swedish study measured magnetic fields inoccupations common among women

Forssn et al. 2004


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Residential exposure assessment

Wire codes crude categorization based on proximity ofresidence to power lines of differentvoltages

Distance to power line alone no consideration of line voltage

Historical calculations Detailed information about power line

configuration and historical load


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Residential exposure assessment

Magnetic field measurements Spot measurements

Long term stationary measurements (24 or

48 h, even up to 7 days) Personal measurements


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Electric bed heating devices

Electric blankets, matress pads, waterbeds

Varying degree of information about habits

of use, duration of use, circumstances ofuse

Most sophisticated estimates in recent

studies


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New studies, occupational exposure

Crudeexposureassessment

No risk increaseoverallIncreased risk forER+ breast cancerafter 10 yr exposure

Interviews.Measurements onconveniencesample, six broadoccupational

groups

VanWijngaardenet al. 2001US

No dose-response

analyses

No risk increaseoverall

Increased risk forPR+ breast cancerwhen exp


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Mix of ELFand RFfieldsNo controlof shift-work

Indication ofincreased breastcancer risk

Norwegian radioand telegraphoperators, no.years * type ofship

Kliukiene etal. 2003Norway

Crudeexposure

assessmentTime >0.1T

No risk increaseoverall

Census data every10thyear

Assessment byOccupationalhygienist


CommentResultsExp. assessmentStudy


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Crudeexposureassessment

Increased risk inelectronic andelectric equipmentmanufacturers

Occupationalhistory. Exposureassessment basedon industry.

Peplonska etal. 2007Poland

Categorizedinto high,medium, low,backgroundexposure

No risk increaseLongest held full-time employment.Assessment byoccupationalhygienist

McElroy et al.2007US



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Swedish occupational study

Case-control study 20,000 cases, 116,000 controls

Occupation from censuses every 5thyear

Exposure assessment: JEM developed for women based on

personal measurements

TWA, maximum exposure, rate of change Control of confounding from age, parity,

socioeconomic statusForssn et al. Am J Epidemiol, 2005


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Female JEM vs male JEM

Forssn, 2004


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Exposure contrasts

Large variation of exposure within many

occupations Identified occupations where a large

proportion of total measurements werehigh Cashiers, working proprietors in retail trade, air stewardesses,

dental nurses, cooks, post office clerks, kitchen maids

And occupations where a large proportionwere low e.g. farmers, primary-school teachers, in-office buyers and

sellers, general public administrative workers, national

insurance office workers


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Swedish occupational study

Results >0.3 TAll ages: 1.01 (0.93-1.10)

50 yr: 1.00 (0.90-1.11)ER+ tumors: 0.98 (0.87-1.11)

All risk estimates are close to 1.0regardless of age, ER-status, duration ofexposure, age at start of exposure etc.


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Occupations with exposure contrast

Overall results: OR=1.03 (0.94-1.13) 50 years at diagnosis: OR=1.06 (0.95-1.18)

ER+ tumors: OR=0.95 (0.84-1.08)


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Residential exposure

Highestquartile0.17 T,analyzedalso 90th

percentile

No indication of riskincrease, regardlessof age, ER-status orexposure metric

24 h bedroommeasurementsWire codes

Schoenfeldet al. 2003US, LongIsland

Lowexposurecutpoint,0.073 T


48 h bedroommeasurementsWire codes

Davis et al.2002US, Seattle



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Residential exposure

Lack ofdose-response

Increased riskrelated to ever beingexposed to magneticfields >0.05 T

Historicalcalculations ofmagnetic fieldsgenerated bypower lines


Highestexposurecutpoint:0.4 T


7 day nighttimebedroommeasurementsWire codes

London et al.2003US, LA



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Includes manyaspects ofuse that couldinfluencelevel of exp.

No indication ofrisk increase,regardlessof age or ER-status

InterviewVery detailedinformation aboutuse of electricblanket

Kabat et al.2003US, LongIsland

Investigatedalso otherappliances no association

No indication ofrisk increase

InterviewEver use andno. of hours/yearnot counting onlyto warm the bed

Davis et al.2002US, Seattle



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Small numberof controls inhighest exp.categorySpeculatesthat African-American

women aremore sensitive

Increased risk,increasing withnumbers of yearsof use

Telephone interviewAny electricbedding deviceEver use andno. of yearsAnalyse separatelyonly to warm the

bed

Zhu et al.2003US,Tennessee



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Summary and conclusions

More than a dozen additional studies afterIARC evaluation

Occupational studies: overall findingsnegative, but indications of increased risksin subgroups in some studies

No consistency regarding the subgroup inwhich increased risks were found


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A large Swedish occupational case-controlstudy with enough power for statisticallystable analyses of the various subgroups

found no effects of the exposure.

Chance is a likely explanation for findings

of increased risks in different subgroupanalyses


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Three well-designed residential studieswith comprehensive exposure assessmentfound no indications of increased risk

One Norwegian residential study found anincreased risk at very low exposure levels;

No obvious reason why this would not beseen also in the US studies should thefinding be true


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Majority of studies of electric bed heatingdevices found no increased risk inludingtwo well designed studies

One study of African-American womenfound an increased risk speculates thatthis is a sensitive subgroup

However, African-American women werealso inluded in one residential study and noeffects were found


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Conclusions

The weight of the evidence available todaysuggests that power frequency magneticfield exposure is nota risk factor for

female breast cancer development

Cannot exclude possibility of minor risk

increase

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Feychting ELF and Breastcancer