Chemical reactions in ventilation systems Ozonolysis of monoterpenes

Jerker Fick

Akademisk avhandling

Som med tillstånd av rektorsämbetet vid Umeå universitet för erhållande av

Filosofie Doktorsexamen vid Teknisk-Naturvetenskapliga fakulteten i Umeå,

framlägges till offentlig granskning vid Kemiska institutionen i KBC-huset,

hörsal KB3B1, fredagen den 3:e oktober 2003, klockan 13:00.

Fakultetsopponent: Charles Weschler, Adjunct Professor, Department of

Environmental and Community Medicine, University of Medicine and Dentistry

of New Jersey, Robert Wood Johnson Medical School, New Jersey, USA.

Copyright © 2003 Jerker Fick

Department of Chemistry Environmental Chemistry

Umeå University SE-901 87

Sweden

ISBN 91-7305-511-5

Printed in Sweden by VMC, KBC. Umeå University. Umeå 2003.

ABSTRACT

Chemicals in indoor air, either emitted from a source or from a reaction, have been suggested to cause ill health in buildings. However, no clear correlations between exposure and health effects have been made.

In this thesis we studied the reaction between monoterpenes, a group of biogenic unsaturated C10 hydrocarbons, and ozone. Ozonolysis of monoterpenes was used as model reactions for unsaturated compounds in ambient air. Also the products formed from these reactions have been suggested as important participants in the occurrence of discomfort and ill health in buildings.

To enable a reliable and sensitive measurement of ppb-ppt levels of monoterpenes and the formed products in the presence of ozone an evaluation of available scrubber materials was made. Potassium iodide was shown to remove ambient levels of ozone and have a recovery of >95% for all monoterpenes and formed products included in the investigation.

Experimental conditions showed to have a large impact on the initial steps of the ozonolysis, and also on the composition of the formed products. We showed that water plays an important and complex role both in the initial stage of ozonolysis of ∆3-carene and in the formation and composition of products from the ozonolysis of α-pinene. The use of experimental design facilitated the evaluation of the investigated reactions. We showed that the formation of OH radicals could be studied using multiple linear regression models and that the presence or absence of OH radicals had a profound impact on the formation of many of the formed products. We also made an observation of the lack of formed OH radicals in the ozonolysis of limonene and discussed probable causes of this observation.

Despite the short reaction times and the ambient levels of ozone and monoterpenes used in our experiments we showed that a number of oxidation products were formed, and that the reaction rate is significantly increased in a ventilation system. This formation is underestimated by theoretical calculations and leads to high amounts of known irritants in the indoor air. We showed that theoretical calculations underestimate the formation of these oxidation products 3-13 times, depending on ventilation system and monoterpene.

Keywords: Monoterpene, Ozone, OH radical, Ozonolysis, Ventilation, Potassium Iodide, Experimental Design, Heat Exchanger.

LIST OF ABBREVIATIONS

ATD Automated Thermal Desorption BSTFA N,O-bis(trimethylsilyl)-trifluroacetamide ECI Excited Criegee Intermediate FID Flame Ionization Detector GC Gas Chromatograph MLR Multiple Linear Regression MS Mass Spectrometer PCI Positive Chemical Ionization PFBHA O-(2,3,4,5,6-pentafluorobenzyl) hydroxy amine PFS Poly(1,4-phenylene sulfide) ppb Parts Per Billion RH Relative Humidity SBS Sick Building Syndrome SCI Stabilized Criegee Intermediate VOCs Volatile Organic Compounds WHO World Health Organization LIST OF PAPERS This thesis is based on the following papers, which will be referred to with Roman numerals (I-IV) I. Ozone removal in the sampling of parts per billion levels of terpenoid

compounds: An evaluation of different scrubber materials. Fick, J., Pommer, L., Andersson, B., Nilsson, C. Environmental Science & Technology, 2001, 35, 1458-1462.

II. A study of the gas-phase ozonolysis of terpenes: the impact of radicals formed

during the reaction. Fick, J., Pommer, L., Andersson, B., Nilsson, C.

Atmospheric Environment, 2002, 36, 3299-3308. III. Effect of OH radicals, relative humidity, and time on the composition of the

products formed in the ozonolysis of α-pinene. Fick, J., Pommer, L., Andersson, B., Nilsson, C.

Atmospheric Environment, 2003, 37, 4087-4096.

IV. The effect of mechanical ventilation systems on the chemistry in the supply air.

Fick, J., Pommer, L., Andersson, B., Nilsson, C. Submitted

The published papers are reproduced with kind permission from the American Chemical Society (paper I) and Elsevier Science (papers II, III).

TABLE OF CONTENTS

1. INTRODUCTION…………………………………………………. 1

2. SICK BUILDING SYNDROME………………………………….. 2

3. OZONE……………………………………….…………….……... 3

4. MONOTERPENES……………………………………………….. 6

5. OZONOLYSIS ………………………………………………...…. 7 5.1. Initial steps…………………………………………………….. 7 5.2. Uni or bimolecular reactions…..………………………..……... 8 5.3. Oxidation by OH radicals………………………..………….… 10 5.4. Ozonolysis of monoterpenes….……………………….………. 11 5.5. Oxidation in the atmosphere…………………………………... 15

6. EXPERIMENTAL DESIGN..……………………………………… 15 6.1. Evaluating experimental designs……………………………… 16

7. MATHEMATICAL MODELLING…………………………….…. 17

8. SAMPLING…………………………………………………………. 17 8.1. Tenax TA………………………………………….……….…. 18 8.2. Gas bubbler…………………………………….……….…….. 18 8.3. Sampling in the presence of ozone……………………………. 19

9. ANALYSIS..…………………………………………………….….. 19 9.1. ATD-GC-FID…………………………………………………. 19 9.2. GC-PCI-MS.…………………………………………………... 20

10. VENTILATION SYSTEMS.……………………………………… 20 10.1. Chemical reactions in ventilation systems………………….... 22

11. CONCLUSIONS AND FUTURE WORKS………………………. 24

12. ACKNOWLEDGEMENTS………………………………………. 26

13. REFERENCES…………………………………………………….. 27

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1. INTRODUCTION The basis of this thesis is that chemicals in indoor air, either emitted from a source or

products from a reaction, have a profound effect on human health. This is not a new

theory. Seneca was frequently advised to leave Rome by his physician and he wrote

to his friend Lucilius in 61 AD that as soon he left Rome's oppressive fumes he felt

better (1). Many reports, observations and regulations since connect air pollution with

adverse health effects (2). For example, Bernardino Ramazzini reported in the

beginning of the 18th century that small rooms become filled with smoke from oil

lamps and gases emitted from humans and that these pollutants penetrate the brain

skull (3).

The specific chemicals we have studied in this thesis are monoterpenes, unsaturated

biogenic hydrocarbons, and the products formed when these react with ozone. We

chose these reactions because they can be used as model reactions for a wide variety

of chemical compounds. Also the products formed from these reactions have been

suggested as participants in the occurrence of discomfort and ill health in buildings

(4, 5). Furthermore, these reactions were studied in an authentic ventilation system to

elucidate the impact of such systems on the chemical reactions that occur in the

ambient atmosphere.

The aim of this thesis was to study the chemical reactions that occur in the ventilation

systems. This aim included:

■ The development of a robust and accurate method for air sampling of

monoterpenes and oxidation products in the presence of ozone. (paper I)

■ Studying the influence of different factors on the oxidation of monoterpenes. (paper

II)

■ Making theoretical calculations of the reactions to be able to compare with and/or

verify the experimental results. (papers II, IV)

■ To investigate which products are formed and what affects the composition of

these. (paper III)

■ Examining the impact of an authentic ventilation system on the oxidation of

monoterpenes. (paper IV)

- 2 -

2. SICK BUILDINGS SYNDROME Historically, the problem with poor indoor air quality was more apparent than

currently. Soot from the ceilings of prehistoric caves provides evidence of the high

concentrations of pollutants that are correlated with the use of open fires in settings

with inadequate ventilation (6). This problem is still the major indoor air quality

problem in the developing countries (7-9). Today, half of the world's population is

exposed to indoor air pollutants from the burning of solid fuels for cooking and

heating, and this exposure is estimated to cause 36% of all lower respiratory

infections and 22% of chronic obstructive pulmonary diseases (10). That this also

was a problem historically was demonstrated by Wells (11) who showed that 1-6% of

the early Britons suffered from sinusitis, an inflammatory disease of the sinus

cavities, that was caused by polluted air indoors. Several observations of poor indoor

and outdoor air have been reported from antiquity and forward, and several reports

clearly stress the relationship between air pollution and health (2). The severe

pollution episodes in London 1873 and 1952, and the increased pollution in Los

Angeles in the 1940's emphasized the hazards of air pollution and intense research

and several regulations followed.

Prior to the 1970's, however, the interest of indoor air quality in the scientific

community was low (12). The name Sick Building Syndrome (SBS) refers to the

diverse affliction that was observed on a large scale in the wake of the oil crises in the

1970's, when the buildings were modified to be more energy effiecient (13, 14). The

term Sick Buildings and Sick Building Syndrome were defined by the World Health

Organization (WHO) in 1983 (13).

SBS is a diverse affliction that includes symptoms like mucous irritation (e.g.,

irritation of the eyes, nose, and throat, skin irritation, odor and taste complaints),

neurotoxic effects (e.g., fatigue, lethargy, headache, nausea, and reduced memory and

concentration), and nonspecific reactions (e.g., chest sounds and asthma-like

symptoms) (13, 15, 16). WHO estimated that 30% of new buildings have poor air

quality (15, 17). SBS has been estimated to affect 19 to 80% of the workers in studies

from North America and Europe (18-20), and is considered to have a multifactorial

etiology that includes exposure to volatile organic compounds (VOCs), bioaerosols,

- 3 -

environmental tobacco smoke, electromagnetic fields, exposure to stress,

psychosocial factors, and other environmental and personal factors (19, 20).

The similarities of the symptoms of the exposure to high levels of VOCs and SBS

(21) have emphasized the theory that VOCs contribute to SBS although no clear

correlations have been made (20, 22). A recent study by Pommer et al. (23) showed a

correlation between the prevalence of SBS and some VOCs, relative humidity, and

building factors. Since the exposure to VOCs is mainly influenced by the ventilation,

a lot of attention have been focused on the correlation between SBS and factors like

ventilation rate, emissions from materials or debris in the ventilation system, types of

ventilation system, etc. (24-26). Increased ventilation rates have been associated with

decreased complaints of SBS and poor air quality (25, 27), but have also been shown

to have no effect (24, 28). Air conditioning was shown to increase the prevalence of

SBS symptoms by 30 to 200% relative to natural ventilation (26).

A possible additional factor is the formation of chemical reaction products (4, 5, 29),

mostly aldehydes, ketones, and carboxylic acids (30-32), but also particles (33-35),

which decrease the quality of the indoor air drastically (36). The oxidized products

are known irritants (37-40), allergenes (41), and some are even carcinogenic (42).

Kreiss et al. (40) presented a study of workers at a microwave-popcorn plant that had

been exposed to 2,3-butanedione and other compounds used as flavoring agents.

They showed a marked increase in respiratory and systemic symptoms and clearly

correlated this to the exposure to the chemicals. Exposure to VOCs indoors has also

been suggested to contribute to the increased prevalence of asthma (14).

3. OZONE Ozone was discovered in 1840 by C. F. Schönbein by anodic oxidation of acidified

water (43) and he named it ozone after the Greek word ozein, to smell, because of its

odor. The correct chemical structure was later elucidated by W. Odling in 1861 (44)

and confirmed by R. C. Brodie in 1872 (45). Ozone is a very pale blue gas, that forms

a blue liquid (b.p. -111.9 °C) and a violet-black solid (m.p. -192.5 °C) (46). Ozone

has a bent triatomic structure with an apex angle of 117° and a bond length of 1.27 Å

(47-49). The ozone structure is best described as a resonance species with four

contributors (50, 51) as shown in figure 1.

- 4 -

Figure 1. Resonance structures of ozone.

Ozone is a strong oxidant and reacts with most organic compounds primarily as an

electrophile (51, 52). In acid solutions the oxidizing potential is only surpassed by a

few reactive species such as fluorine, OH radical, etc. (53). Ozone also reacts with

compounds in the gas-phase. At room temperature, however, the gas-phase reaction

rates constants for most organic compounds are too low to lead to any significant

oxidation, with the exception of alkenes (29, 54). Alkenes reacts readily with ozone

with rate constants in the range of 10-16 - 10-18 cm3 molecule-1 s-1 at room temperature

(54), which leads to a significant oxidation in the ambient atmosphere indoors and

outdoors.

Ozone has a characteristic odor, detectable at 10 parts per billion (ppb), and is very

toxic (55). Concentrations exceeding 120 ppb have been suggested to affect healthy

adults, but children and other sensitive individuals such as asthmatics react at lower

concentrations (55, 56). Ozone has been shown to cause damage to the lung, blood

and central nervous system (57). This damage is caused by an inflammatory process,

which liberates free radicals (58), as well as by formed oxidation products (59).

Ozone also causes damage to vegetation and the levels of ozone in the ambient air are

high enough to have an adverse effect on plants (60). Exposure to ozone leads to

effects on the yields and quality of cereal crops (61, 62), and cause reduction in

growth and biomass of forest trees (63, 64). Ozone exposure also leads to an

increased susceptibility to secondary stress (64) and can alter the composition of

natural ecosystems (65).

Ozone is formed in the stratosphere (figure 2) by the dissociation of O2, through a

mechanism first proposed by Chapman (66) as presented in equation 1, 2.

O2 + hv → O + O (1)

O + O2 + M → O3 + M (2)

Where hv = < 242 nm and M is a neutral third body (usually N2 or O2) (67).

- 5 -

Figure 2. The lower part of the atmosphere.

Most of the ozone is present in the stratosphere at altitudes of 15-35 km in the so-

called ozone layer. This ozone layer absorbs most of the suns ultraviolet light (hv

=230-320 nm), equation 3 (67).

O3 + hv → O2 + O (3)

Ozone is also present in the troposphere (figure 2). Some is transported down from

the stratosphere through folding events and diffusion, and some is produced by

dissociation of NO2. Ozone production in the troposphere is governed by a complex

interplay between OH radicals and the VOCs/NOx ratio, where an increase in VOCs

leads to more ozone and an increase in NOx can either decrease or increase the ozone

level depending on the ratio (67). This means that the level of ozone is higher in

polluted urban areas and lower in rural areas. Ozone levels in remote rural areas

average between 20-45 ppb (68, 69) but in polluted urban areas the ozone level can

reach as high as 400 ppb (67). Ozone levels increase with approximately 1% a year

(70, 71) and the levels of tropospheric ozone has more than doubled in Europe since

the beginning of the 20th century (68). This is due to increased levels of pollutants in

the troposphere, mainly from transportation (67).

Ozone is also present indoors at levels of 20-80% of those outdoors (72-75). Indoor

concentration of ozone is affected by the ventilation and air exchange rates (72, 76)

and follows closely the concentration of the outdoors levels of ozone (75). Ozone

- 6 -

reacts rapidly with sinks in the indoor setting like carpets and other surfaces (75, 77-

80), which lowers the ozone levels indoors.

4. MONOTERPENES Monoterpenes is a group of C10 biogenic alkenes, which are emitted by vegetation

(figure 3). In some families such as the Pinaceae (e.g., pine, fir) and Lamiaceae (e.g.,

mint, basil) almost all species emit monoterpenes; they are also emitted by many

other species from a wide range of families (81, 82). The monoterpenes have boiling

points in the range 150°–185° C, and are all very fragrant with an odor threshold in

the ppb range; they are often used as additives in cleaning products (83).

α-pinene β-pinene Limonene ∆3-Carene ∆2-Carene

Myrcene Terpinolene Camphene Sabinene β-Phellandrene

Figure 3. Some monoterpenes.

Monoterpenes have been shown to deter herbivores and attract pollinators (81, 84).

Monoterpenes were suggested to protect against thermal stress and have been shown

to increase the thermotolerance of the photosynthetic apparatus by stabilizing the

thycaloid membranes (85). Peñuelas and Lluisà (86) showed that monoterpenes also

protected against photodamage, especially at elevated temperatures.

Guenther et al. (87) calculated that monoterpenes account for approximately 1.0

x1013 g carbon of the annual emission of biogenic hydrocarbons in North America

- 7 -

and approximately 1.27 x1014 g carbon year-1 globally (88). Monoterpenes account

for 10% of the total global emission of non methane volatile organic compounds,

which is estimated at approximately 1.3x1015 g carbon year-1 (67, 88), and at the

same level as the total anthropogenic contribution (67). In a typical coniferous forest

the monoterpene concentration is 0.01-5 ppb depending on the time of day, season

and location (89, 90). Temperature has the greatest influence on the emission as it

increases the production and emission rates of most monoterpenes exponentially up

to a maximum, beyond which enzyme degradation and other physiological processes

changes the emission (91, 92). This strong dependency on temperature has raised the

question if the global warming has started to affect the amount-emitted of

monoterpenes (81). A recent calculation stated that global warming over the last 30

years has increased the biogenic volatile organic compounds emission by 10% and a

rise of 2-3 ºC this century would results in an additional 30-45% (93).

Monoterpenes are also present indoors due to emissions from floors, walls and

furniture made out of wood, as well as transport from the outdoor air (22). The indoor

levels of monoterpenes actually often exceed that of the outdoor air (22, 94), and in

new/newly furnished buildings the VOCs and monoterpenes levels can be

considerable elevated (22). Levels above 400 ppb α-pinene have been detected in

specific indoor settings (22).

5. OZONOLYSIS

The gas-phase reaction between ozone and alkenes is a complex multi-step reaction

(95, 96) that has received a lot of attention recently because it plays a major role in

various urban air pollution phenomena, e.g., formation of particles (33, 35, 97-99),

and as important precursors in the formation of tropospheric ozone and OH radicals

(100-107).

5.1. Initial steps.

The reaction starts with a 1,3-dipolar addition of ozone, which yields a 1,2,3-

trioxolane product (96, 108, 109), which is shown in figure 4. This 1,2,3-trioxolane

product is thermally unstable and rapidly rearranges into a vibrationally excited

- 8 -

carbonyl oxide called the excited Criegee intermediate (ECI) and a carbonyl

(aldehyde or ketone depending on the substituents) (50, 108-111), figure 4.

R

RR

ROO

OR

R

OOO

R

R

R R

OO

R R

O

+

#

.

.

Figure 4. Initial steps of ozonolysis.

Based on structural calculations (112, 113), ECI adopts the carbonyl oxide structure.

Adam et al. (114) calculated that the activation energy prevents a cyclization of

carbonyl oxide to dioxirane. The initial steps of the ozonolysis are now reasonably

understood even though significant uncertainties remain, e.g., it has been suggested

that the addition of ozone may not only be a concerted mechanism but also a partial or

stepwise addition (115).

5.2. Uni or bimolecular reactions

ECI can either be collisionally stabilized by a third body (nominated M in figure 5),

decomposed or isomerized (figure 5).

RR

HOO

O O

R R

RR

O

O O

R RR R

OO

R R

OO

R R

OO

R R

OO#

#

#

M

#

OH. + .

Products

or

#

#

.

.

#

.

.

#

.

.

.

.

.

Figure 5. Different reaction pathways for excited Criegee intermediate (ECI).

- 9 -

There are still some questions about the structure of the stabilized Criegee

intermediate (SCI). Theoretical calculations indicate it can form a carbonyl oxide or a

dioxirane (116). Please note that the SCI may not be a carbonyl oxide but a dioxirane

(figure 5). Yields of 3-40% (117-122) of SCI have been reported. These

measurements are all based on the detection of formed products and not on direct

observations. Kroll et al. (107, 123) observed a pressure dependency in the OH

radicals formation for a number of small alkenes. Their method includes the direct

detection of OH radicals with laser-induced fluorescence at various pressures and at

very short reaction times (107). Kroll et al. (107, 123) also states that larger alkenes

will have more vibrational modes and therefore be even more susceptible to

collisional stabilization and report a weak but existent trend of this in their series of

alkenes. Other groups (124, 125) have also reported observations of pressure

dependant reactions. These findings imply that most of the ECI from the ozonolysis of

monoterpenes will be collisionally stabilized and put the emphasis on possible

consecutive bimolecular reactions.

SCIs have been reported to react with H2O (115, 122, 126-128 and paper III), SO2

(115, 119, 126), aldehydes (115, 126), and NOx (115, 126). Some authors have even

suggested that the SCI can react with alkenes (96, 129 and paper II). Crehuet et al.

(130) calculated that the reaction between a SCI and an alkene would proceed through

a similar transition state as that of the ozone-alkene reaction, and yield 1,2-

dioxolanes. A number of other reaction pathways between SCI and various

compounds have been reported (96, 122, 127, 131 and paper III), and the most

relevant reaction is the reaction between SCI and H2O. Even though the reaction rate

is slow (an estimated upper limit at 10-16 cm3molecule-1s-1) (132), H2O is so abundant

in the atmosphere that it will dominate over all other reaction pathways. Ryzhkov and

Ariya (128) suggested recently that the SCI reacts with a water dimer and that this

pathway is more energetically favorable than the reaction with water as calculated by

other groups (131, 133). SCIs that reacts with water form the corresponding α-

hydroxy hydroperoxide (122, 127, 134-137) as shown in figure 6.

- 10 -

R R

OHHOO

Figure 6. An α-hydroxy hydroperoxide.

α-Hydroxy hydroperoxides have been isolated in the atmosphere (138) but they

dissociate and form a variety of products (135, 139, 140).

One of the unimolecular reactions available to the ECI is the isomerization and

formation of an excited 5 membered hydroperoxide intermediate, which dissociate

and forms an OH radical and a peroxy radical (104, 110) as shown in figure 5. This

pathway requires an alkyl group adjacent to the ECI, i.e., the ECI needs to be

monosubstituted syn or disubstituted. Experimental data from Kroll et al. (107, 123)

indicate that at atmospheric pressure most of the formed OH radicals are formed from

the thermal dissociation of SCI. Kroll et al. (107, 123) state that even though almost

all of the ECI is stabilized, unimolecular reactions will dominate the reaction scheme

and will primarily lead to thermal dissociation to form OH radicals (123, 141).

The ECI may also ring closure to dioxirane (100, 110) as shown in figure 5. This

route is also called the "hot ester channel". The isomerization to dioxiranes seems to

be hindered if the CI is disubstituted or monosubstituted syn, but may occur as in the

unsubstituted case (100, 123). Calculations show that alkyl substituted bisoxy radicals

prefer the ester rearrangement decomposition (142), but the further fate of this

reaction pathway is unknown (123).

5.3. Oxidation by OH radicals

The major initial reaction pathway involves OH radical addition to either carbon in

the double bond to form β-hydroxyalkyl radicals (54, 143) (figure 7).

R

RR

RR

RR

ROH

OH. + .

Figure 7. Addition of OH radicals.

- 11 -

In addition to the addition pathway, H-atom abstraction from the C-H bond of alkyl

substituents adjacent to the double bond occurs as a minor process (54, 143) (figure

8).

R

RR

R

R

RR

R

OH. + + H2O.

Figure 8. H-Abstraction by OH radicals.

5.3. Ozonolysis of monoterpenes

The ozonolysis of monoterpenes has been studied extensively and the reaction rates

are well known (54) and are presented in table 1.

Table 1. Reaction rates with ozone and OH radical formation yields of some monoterpenes.

Monoterpenes Reaction rate a Lifetime b OH radical

formation c

α-Pinene 86.6 4.6 h 0.85

β-Pinene 15 1.1 day 0.35

Limonene 200 2.0 h 0.86

∆3-Carene 37 11 h 1.06

∆2-Carene 230 1.8 h d

Myrcene 470 50 min 1.15

Terpinolene 1880 12 min 1.03

Camphene 0.9 18 days <0.18

Sabinene 86 4.6 h 0.26

β-Phellandrene 47 8 h 0.14

a 1018 x k (at 298 k) (cm3 molecule-1 s-1) (54).

- 12 -

b Time for decay of compound to 1/e (37%) of its initial concentration at an ozone concentration of 28 ppb (143) c Molar yield of OH radicals (102). d No value reported.

The monoterpenes react readily with ozone and the ozonolysis also generates OH

radicals (table 1). Any system involving ozonolysis of monoterpenes therefore

includes the presence of OH radicals. These OH radicals can be quenched, i.e., a

compound is added that reacts faster with the OH radicals than the compounds studied

(102, 103, 144), in order to study the effect of ozone itself.

This thesis focused on the OH radical production (paper II) and the experimental

settings impact on the initial ozonolysis (paper II) and the product composition (paper

III).

In paper II we studied the OH radical formation and the impact of the experimental

settings on the initial ozonolysis of three monoterpenes, α-pinene, ∆3-carene and

limonene. We made theoretical mathematical calculations, based on known reaction

rates, of the various reactions in order to compare predicted amounts reacted with our

experimental data. When comparing the experimental results with the predicted

values it was shown that the ozonolysis of the different monoterpenes was faster than

predicted for all monoterpenes. We showed that α-pinene, ∆3-carene and limonene

reacted 1.37, 3.79, and 1.61 times more than predicted, respectively. A hypothesis that

this was due to reactions on surfaces was presented.

We also showed that the OH radical formation of both α-pinene and ∆3-carene were

possible to study using an experimental design. We observed that the ozonolysis of

limonene apparently did not produce OH radicals; an observation that directly

contradicts other studies (102, 145, 146) and that which is not consistent with the

most acknowledged theory (104, 147). An alternative reaction pathway between the

SCI from the ozonolysis of limonene and limonene itself was suggested-a pathway

that has been proposed previously (96, 129, 130).

- 13 -

In paper III we focused on the products from the reaction between α-pinene and

ozone, and the impact of the experimental settings on the composition of these

products. The reported products from the reaction between α-pinene and ozone are

shown in table 2.

Table 2. Detected products in published chronological order from the ozonolysis of α-pinene. References in parenthesis.

O

O

Pinon aldehyde

O

O Norpinon aldehyde

O

O

OH

Pinonic acid

OH

O

O Norpinonic acid

O

O

Glyoxal

(30, 31, 97, 136, 148-156) Paper III

(31, 148, 150, 152, 154, 155) Paper III

(31, 148-152, 154, 155) Paper III

(31, 148, 150, 152, 154, 155) Paper III

(149, 150) Paper III

O

α-pinene oxide

OOH

O

OH

Pinic acid

OO

Methyl glyoxal

C9H14O3 Norpinonic acid isomer

OH

O

O

OH

Norpinic acid

(136) (31, 150-152, 154, 155) Paper III

(150) Paper III

(31, 150-152, 154, 155) Paper III

(31, 151, 152, 154, 155)

O

O

OHOH

10-Hydroxy pinonic acid

O

OHO

a

O

O

b

O

O

O

c

C10H14O3

(31, 151, 152, 154, 155)

(31, 152, 155)

(31, 152, 154, 155)

(31) (31, 152, 154, 155)

a 3-formyl-2,2-dimethylcyclobutanecarboxylic acid

b 2,2-dimethylcyclobutane-1,3-dicarbaldehyde

c (3-acetyl-2,2-dimethylcyclobutyl)methyl formate

Other products that have been reported are CO (148), CO2 (148), formaldehyde (148,

149, 157), formic acid (148, 157), acetone (149, 157, 158), and C10H16O (136). Jaoui

and Kamens (154, 155) reported some additional products including 1 and 10-

- 14 -

hydroxypinon aldehyde and campholene aldehyde but it should be noted that their

experiments were conducted in the presence of both ozone and OH radicals.

Oxidation by OH radicals also generates pinon aldehyde as the most prominent

product (32, 159-161) and a variety of additional products have been reported e.g.,

campholene aldehyde (32), hydroxy and dihydroxycarbonyls (159, 161, 162) and

acetone (159). OH radicals can also react with the formed products and form a wide

variety of additional products (163-168).

In paper III we investigated how experimental settings affected the composition of the

products formed in the ozonolysis of α-pinene. We detected pinic acid, glyoxal,

methyl glyoxal, norpinonic acid and norpinonic acid isomer, pinonic acid, an

unidentified C4 dicarbonyl (C4H6O2), an unidentified C5 dicarbonyl (C5H8O2),

norpinon aldehyde, and pinon aldehyde (table 2). Rohr et al. (39) showed that

products from the ozonolysis of α-pinene have adverse effects on both the upper

airways and the pulmonary regions. That reaction products from various chemical

reactions, especially ozonolysis, can contribute to cause ill health in a population have

been suggested by several researchers (4, 5) and the findings of Rohr et al. (39)

strongly supports this theory.

We showed that water plays a pivotal role in the reaction scheme increasing the

reaction rate for some products (i.e., pinic acid, glyoxal, methyl glyoxal and pinon

aldehyde) and decreasing the yield of pinonic acid. Pinonic acid, norpinonic acid and

an isomer of norpinonic acid were shown to be more or less solely formed from the

reaction of α-pinene and OH radicals.

We also presented a novel route to the formation of pinic acid, which was supported

by experimental observations. In addition we presented a route to the formation of (3-

acetyl-2,2-dimethylcyclobutyl)methyl formate (table 2), a product that was observed

by Yu et al. (31).

- 15 -

5.5. Oxidation in the atmosphere

In principle all hydrocarbons in the atmosphere will eventually be oxidized and form

CO2 and H2O (67). This process is, however, a complicated and lengthy one, and a

wide variety of more or less stable products are formed (67, 143). A simplified

reaction sequence of the reaction between the OH radical and methane (67), the most

common and simple hydrocarbon in the atmosphere, illustrates this as presented in

equation 4-14.

CH4 + OH. → CH3

. + H2O (4)

CH3. + O2 + M → CH3O2

. + M (5)

CH3O2. + NO → CH3O

. + NO2 (6)

CH3O2. + HO2

. → CH3OOH + O2 (7)

CH3O. + O2 → HCHO + HO2

. (8)

HO2. + NO → NO2 + OH

. (9)

CH3OOH + hv → CH3O. + OH

. (10)

CH3OOH + OH. → HCHO + H2O + OH

. (11)

CH3OOH + OH. → H2O + CH3O2

. (12)

HCHO + OH. or hv → CO + H2 (13)

CO + OH. → CO2 + H

. (14)

The atmospheric fate of the more complex monoterpenes is not a straightforward

reaction pathway to CO2 and H2O. It is a complex reaction scheme that starts with

oxidation by ozone, NO3 or OH radicals, and includes the formation of particles,

radicals and stable products, which we have just begun to understand (143).

6. EXPERIMENTAL DESIGN Experimental design covers a number of techniques where the objective is to obtain as

much information as possible with as few experiments as possible (169). The scope is

to explain the change in response caused by variations in the different experimental

parameters when all the experiments are combined using multiple linear regression

- 16 -

(MLR). MLR is a statistical method that calculates a mathematical equation (a

model), using the parameters mean response differences between high and low

settings (169). Experimental designs have been used extensively in this thesis (papers

II-IV).

The experiments are done according to a planned design, where a full factorial design

yields the most information, and fractional design provides an option to decrease the

number of experiments with a minimum loss of information. Additional experiments,

so called centerpoints, are often added at the mean setting between the high and low

setting. Centerpoints enable the calculations of lack of fit and the experimental error

at 95% confidence interval, and also enables the detection of curvature.

6.1. Evaluating experimental design

The model correlates the settings of the different parameters with the corresponding

result. This correlation, which is measured by R2 and Q2, shows to what degree the

experimental data can explain the results. The R2 value shows how much of the

variance in the data is explained, and the Q2 value explains how well the model can

predict omitted values. This Q2 value is calculated by omitting existing values and

then replacing them with values calculated by the model; these values are then

compared, i.e., a cross-validation (169).

The results from the design are presented in two different ways, in contour plots and

as effect terms as shown in figure 9.

Figure 9. A contour plot of amount reacted (left) and effect terms (right) from an

investigation of the ozonolysis of α-pinene (paper II).

A contour plot is a graphic presentation of the MLR calculation at the specific

experimental settings and presents the response in the investigated region. The

designs enable us to make contour plots for all the regions within the experimental

settings. This is a powerful tool to study the details of the reaction and to predict the

- 17 -

amounts reacted at a specific setting. The effect terms show what impact the different

parameters had on the reaction, i.e., the change in impact when one parameter is

raised from the low to the high setting and all the other parameters are kept at their

centerpoints values. The main effects are calculated as the difference between the

averages of the high and low setting of the individual parameters. The interaction

effects are calculated as the difference in response between the average of both

parameters effects when both are at the high or low setting and the average in

response of the parameters effects when they are at opposite settings. Thus the

interaction term measures the synergistic effects of the main parameters, i.e., the

effect of one parameter depends on the level of another parameter.

7. MATHEMATICAL MODELLING The mathematical modeling in this thesis (papers II, IV) were used to predict the total

amount of reacted monoterpene and to calculate the quotient between the amounts of

monoterpene reacted with OH and ozone. A reaction model was formulated for the

different ozone-monoterpene reactions that included all the reactions that had an

impact on the initial stages of the ozonolysis. FACSIMILE, the software used (170),

calculated the partial differential equations of each chemical reaction and solved these

equations by integrating and averaging over small time intervals (cells). Some

approximations were made, but these were valid as long as the cells were small. The

mathematical models used in this thesis calculated only the initial step of the

ozonolysis and the reactions that were included in the reaction model were those that

had a direct effect on the amount of monoterpenes and the reactive species that

reacted with the monoterpenes. No attempt was made to calculate the distribution of

the various products because of the complexities and uncertanties involved.

8. SAMPLING A number of techniques that are available to sample VOCs in air are, cryogenic

methods, solid sorbents, gas bubblers, derivatisation on solid support

(chemosorption), whole air sampling, etc. Many of these methods are also possible to

combine in order to enhance the sampling efficiency for individual compounds (150,

171-176). Two of these methods, solid sorbent sampling using Tenax TA as

- 18 -

adsorbent (paper I, II, IV) and gas bubbler sampling (paper III) have been used in this

thesis.

8.1. Tenax TA

Tenax Ta is a 2,6-diphenylene oxide polymer, which is suitable for sampling VOCs

in the C7-C26 range (171, 176, 177) and is extensively used for sampling

monoterpenes (178). Tenax TA adsorbs the VOCs through dispersion interactions

supported by dipole-type interactions (179); however, this adsorption is a

physisorption process and enables recoveries of 100% (180, 181). Tenax TA is

hydrophobic and thermally stabile (176) but is prone to degradation in the presence of

ozone (182) and other reactive species (183).

8.2. Gas bubbler

Sampling with a gas bubbler was used in this thesis (paper III) to enable the detection

of oxidation products from the ozonolysis of α-pinene. Gas bubblers contain liquids

that extract compounds from the air sample that is pumped through and this method is

used for collecting polar, reactive and high-boiling compounds (171, 184, 185). This

method is also convenient to combine with different derivatizing methods (171, 184).

Yu et al. (150) reported a method that made it possible to simultaneously detect

products with a diverse range of functional groups and this method was used in paper

III. The method derivatizes carbonyls, alcohols, and acids and also derivatizes

multifunctional compounds. The carbonyls were derivatized using O-(2,3,4,5,6-

pentafluorobenzyl) hydroxy amine (PFBHA) and the acids and alcohols were

derivatized using N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) as a silylation

agent. The formed oxime and silyl derivates are shown for pinonic acid in figure 10.

ON

O SiOF

F

FF

F

OO

OH

1 PFBHA2 BSTFA

Figure 10. The derivatization method for carbonyls, alcohols, and acids.

The derivatized samples should be analyzed witin 12 h, in order to minimize the risk

of samples breaking down. We have observed some losses of sampled compounds

that have been stored in room temperature for more than 24 h.

- 19 -

8.3. Sampling in the presence of ozone

A potential problem in the sampling of VOCs in air is reactions between the

concentrated sampled compounds and reactive species in the air. Most studies have

focused on ozone, which is a reactive specie that is present in high concentrations

(182), but interferences by NO2 have also been reported (183). Ozone has been

shown to react with unsaturated compounds, which leads to an underestimation of the

concentration in the sample and artifact formation (182, 186, 187). Losses of 8-97%

have been reported for monoterpenes in the presence of 23-50 ppb ozone (172, 187,

188) and various artifacts have been presented (182, 189-191). Oxidation reactions

during sampling can be reduced or eliminated by selectively removing the oxidant

prior to the adsorbent. A number of different chemicals have been used to remove

ozone, e.g., potassium iodide, cotton, sodium carbonate, sodium sulphite, etc. Helmig

(182) presents most of these in his excellent review article.

In paper I we examined a number of these chemicals with regard to ozone removing

properties and recovery of some terpenoid compounds. We showed that most

chemicals investigated were capable of removing ambient levels of ozone (potassium

iodide, poly(1,4-phenylene sulfide) (PFS), manganese dioxide, and sodium sulphite).

Only potassium iodide, however, had high recoveries of the tested compounds, i.e., a

recovery of >95% for monoterpenes and some of their reaction products.

9. ANALYSIS Analysis of VOCs is conducted using a wide variety of analytical methods and

techniques (173, 175, 192, 193). All of the methods have advantages and

disadvantages and are more suitable for certain groups of compounds then others.

Two of these methods, ATD-GC-FID (papers I, II, IV) and GC-PCI-MS (paper III)

have been used in this thesis.

9.1. ATD-GC-FID

Automated thermal desorption (ATD) injector connected to a gas chromatograph

(GC) using a flame ionization detector (FID) is commonly used in the detection of

e.g., monoterpenes (178), and is also widely used in various other applications (173).

The sample is thermally desorbed from a solid adsorbent onto a cold trap, which then

is rapidly heated and the sample is injected on a GC column. The components in the

- 20 -

sample are separated on the column and detected by the electric current that is formed

when the carbons in the compounds are ionized in the hydrogen flame in the FID. All

carbons in the different compounds yield signals; hence the total amount of carbon

present at a specific moment is detected.

9.2. GC-PCI-MS

Gas chromatography (GC) using positive chemical ionization (PCI) mass

spectrometry (MS) provides a method to analyze a number of oxidation products that

are relevant in atmospheric chemistry and this method is used extensively (31, 150,

154, 194, 195 and paper III). PCI is a soft ionization technique that produces ions

with little excess energy, which leads to less fragmentation than a hard ionization

method (e.g., electron ionization) (196). This technique often yields the protonated

molecular ion ((M+H)+) as the base peak. PCI uses a reagent gas, usually methane

(paper III), isobutane or ammonia, which is ionized by a electron beam to produce

thermal electrons and reactant ions, as shown with methane in equation 15. Reactant

ions will collide with other methane molecules and form CH5+, which will protonate

the sample in an acid-base type of reaction (equation 16 and 17).

CH4 + e- → CH4.+ + 2e- (15)

CH4.+ + CH4 → CH5

+ + CH3. (16)

CH5+ + M → (M+H)+ + CH4 (17)

Some methane ions will fragment, however, and these fragments will also react with

methane and yield, e.g., C2H5+ and C3H5

+. Some of these will also protonate the

sample and yield M+29 and M+41 adducts, which facilitates the identification of the

molecular ion.

The formed ions are then separated by their mass to charge ratio in an electric or

magnetic field, detected and amplified (196).

10. VENTILATION SYSTEMS Ventilation systems in a building have two main objectives, to supply fresh air and to

remove polluted air. In domestic and commercial buildings humans and the building

material pollute the indoor air. A human emits 18 L/h CO2, 40 g/h water and various

- 21 -

odors, and the policy, introduced by Yaglou et al. (197) in the 1930's, has been to

have a flow of air that removes these effluents so that >80% of the occupants

consider the indoor air quality to be acceptable. Recently the building and building

materials have also been recognized as pollution sources, and since VOCs emitted by

the building materials have an odor threshold that is lower than the airway irritation

estimates (198), the air flow has to be adapted to remove those pollutants as well

(199). These goals can be achieved with increasingly complex ventilation systems.

The most basic ventilation is called natural ventilation and the air is transported in

and out of the building through windows, slits, poorly isolated walls, etc. Natural

ventilation has no additional systems that supplies or removes air but can be built

with specialized exhaust vaults, which generates a slight under-pressure in the

building that removes the air (figure 11). In these buildings the ventilation ducts are

normally on the exhaust side only as the supply air enters the building directly

through slits.

Mechanichal systems depend on fans to supply and remove the air and there are two

types, systems that only have exhaust fans and systems that have fans for both the

exhaust and supply air. In buildings with exhaust fans only the supply air enters

directly into the building through slits and the exhaust air is removed through

ventilation ducts (figure 11). In buildings with exhaust and supply fans the supply air

is transported through ventilations ducts to the different rooms in the building. The

exhaust air is then removed through a different set of ventilation ducts (figure 11).

Buildings with both an exhaust and supply fan need to be more or less air-proof in

order to maintain the equilibrated flow between the fans.

Figure 11. Different ventilation systems. Natural ventilation (left), exhaust fan only

(middle), exhaust and supply fans (right).

- 22 -

There is a number of additional functions that can be applied to the ventilation system

and a number of different technical solutions to the specific requirements of

architects, building owners, occupants, climate, etc. A heating or cooling system is

often added, to the supply air in buildings with both a supply and exhaust fan.

Different techniques are used. Some use a heating coil in the supply air and some use

a heat exchanger that transfers the heat from the exhaust air to the supply air; these

can also be combined with the heating coil, etc. Two types of heat exchangers were

used in this thesis (paper IV), a rotary and a cross flow. The basic principle behind a

heat exchanger is to transfer the heat from the exhaust air to the incoming supply air.

In a rotary heat exchangers this heat transfer is conducted with a rotor that slowly

rotates between the exhaust and supply air. The rotor has a large surface area and this

leads to a high efficiency (80-90%). In a cross flow heat exchanger the heat transfer is

conducted by a grid of thin parallel channels. The supply air is not exposed to the

exhaust air (unless there are minute cracks present) and the heat transfer occurs

through the channel walls. A cross flow heat exchanger has a moderate surface area

and is less efficient (50-60%). Cooling is also often integrated in the ventilation

system and a number of techniques exist that are often referred to as air conditioning.

Some buildings reuse the exhaust air after it has passed some filters and has been

added with various amounts of outdoor air. Other additional functions include air

humidifier, various filters (for particles and/or chemicals), vibration dampers, etc.

10.1. Chemical reactions in ventilation systems.

Chemical reactions in the atmosphere are governed by the presence and absence of

sunlight that determines the composition of VOCs and OH and NO3 radicals (67).

Chemical reactions in the atmosphere are also considered to occur almost exclusively

in the gas-phase even though some heterogeneous reactions have proven to be vital

(67). In a ventilation system these two differences, a high surface to volume ratio and

complete darkness, alter the outcome and reaction rates of the chemical reaction that

occur.

The lack of sunlight will stop the photo dissociation of formed products and also the

dissociation of NO2, which lead to a decreased formation of OH radicals and ozone.

Absence of sunlight will also stop the dissociation of any formed NO3 radicals, which

could lead to an increased overall reactivity (67) so the net result is hard to predict.

- 23 -

Galvanized sheet metal, the primary surface material in most ventilation ducts, has a

Zn coated surface that has "islands" of ZnO (200-202). ZnO provides active sites that

could dissociate ozone and form molecular oxygen (203), which would form OH

radicals and increase the overall reactivity of the system. Bulanin et al. (203)

suggested that the ozone acts as a Lewis base and forms complexes with weaker

Lewis acids, and decomposes on sites with stronger Lewis acids. Zn and/or aluminum

(e.g., surfaces in the heat exchangers) have been shown to produce different

adsorption complexes with ozone, which supports this theory (51, 204). Smith (205)

stated that Zn is the most common reducing agent used to produce aldehydes and

ketones in liquid phase ozonolysis. This clearly shows that the surfaces present are

likely to have a high reactivity towards the products formed from ozone reactions.

In paper IV we studied the reaction between three monoterpenes (α-pinene, ∆3-

carene, limonene) and ozone in an authentic ventilation system. The ventilation

system consisted of an interchangeable heat exchanger (two different heat exchangers

were used, a cross flow and a rotary), 75 m ventilation duct, gas-phase generation

equipment, ozone and NOx monitoring devices and filters, etc, as shown in figure 12.

Figure 12. The experimental set-up: Charcoal filter (A), ozone inlet (B), air inlet (C),

micro-syringe injector (D), mixing zone (E), monoterpene and ozone sampling (F, H,

I), heat exchanger (G), valves (V 1-3). Please note that this figure depicts a cross flow

heat exchanger.

We observed that the ventilation system had a profound impact on the ozonolysis of

all investigated monoterpenes. When compared to a theoretical mathematical

- 24 -

calculation, based on the rate constants of all significant reactions, all monoterpenes

reacted more than predicted. These increases were significant, as shown in table 3.

We showed in paper IV that the ozonolysis of the monoterpenes were affected by the

experimental settings like surface area, amount of water, level of ozone and

interactions between these.

Table 3. The calculated (FACSIMILE) and measured amounts of reacted monoterpene.

α-pinene ∆3-carene limonene

Mathematical Calculationsa 2.2% 1.0% 5.3% Paper IIb 2.7% 3.7% 9.3% Cross flow heat exchangerc 5.5% 6.0% 9.2% Rotary heat exchangerc 12.5% 12.9% 14.8%

a Calculated (FACSIMILE) for 20 ppb monoterpene, 75 ppb ozone, and 75 s. b Obtained from the MLR models at the experimental settings 20 ppb monoterpene, 75 ppb ozone, and 75 s. c The experimental settings were 20 ppb monoterpene, 75 ppb ozone, 28.3 m2 ventilation duct surface area, and 75 s (paper IV). We also showed that the rotary heat exchanger itself increased the amount reacted in

addition to increasing the amount reacted in the ventilation duct.

11. CONCLUSIONS AND FUTURE WORK The main observation of this thesis is that reaction products are formed in ventilation

systems. Despite the short reaction times and the ambient levels of ozone and

monoterpenes used in our experiments, we showed that a number of oxidation

products were formed (paper III) and that the reaction rate is significantly increased

in a ventilation system (paper IV). This formation is underestimated by theoretical

calculations and leads to high amounts of known irritants in the indoor air. The

oxidation products formed have been suggested to contribute to the occurrence of

SBS (4, 5), and have been shown to cause adverse effects on the respiratory system in

mice (39). We show in paper IV that theoretical calculations underestimate the

formation of these oxidation products 3-13 times, depending on ventilation system

and monoterpene. Different factors that affect the ozonolysis of monoterpenes in

ventilation systems were also studied. We showed that the surface area and type of

heat exchanger affected the reaction rate for all monoterpenes.

- 25 -

In paper I we show that a potassium iodide scrubber enables sampling in the presence

of ozone without loss of the sampled compounds and additional oxidation. This

scrubber was used in all papers included in this thesis and its use is recommended

when sampling monoterpenes and their oxidation products in an ozone rich

environment.

In papers II and III the effect of the experimental conditions on the initial steps in the

ozonolysis was investigated, and also how these conditions affect the composition of

formed products. We showed that water plays an important and complex role both in

the initial stage of ozonolysis of ∆3-carene and in the formation and composition of

products from the ozonolysis of α-pinene. The use of experimental design facilitated

the evaluation of the investigated reactions. In papers II and III the impact of the OH

radicals that were formed in the ozonolysis were also studied. We showed that the

formation of OH radicals could be studied using multiple linear regression models

and that the presence or absence of OH radicals had a profound impact on the

formation of many of the formed products. We also made an observation of the lack

of formed OH radicals in the ozonolysis of limonene and discussed probable causes

of this observation.

Regarding future work, it would be very interesting to elucidate the precise nature of

the interaction/catalytic effect of the surfaces in the ventilation system. The impact of

other factors, e.g., additional heating, presence of NO3 radicals, etc, would be really

interesting to include in an investigation.

It would also be very interesting to examine the limonene-ozone reaction in greater

depth, preferably in additional experimental set-ups, to be able to confirm and explain

or disregard our observation. Work needs to be done in order to elucidate the role of

water in the initial steps of ozonolysis and its interaction with the formed products.

Also much more work needs to be done in general in the field of indoor air chemistry

in order to minimize the discomfort experienced by many. I believe that an

epidemiological study that includes the measurement of oxidation products would be

able to correlate chemical compounds in the indoor air with the occurrence of SBS.

- 26 -

12. ACKNOWLEDGEMENTS Tanken här är att man ska tacka alla dom som hjälpt en att nå ända hit. En uppgift

som egentligen inte är svår utan snarare väldigt tacksam, men ni är ju så många och

jag har så mycket att tacka för. Omnämnandena kommer i en löst förvirrad

vetenskaplig ordning.

Jag börjar med mina handledare Barbro och Calle som visat mig hur man gör. Barbro

tack för stöd, tillgänglighet och alla kloka ord både om forskning och annat. Du har

hjälpt mig att hitta mitt sätt att undersöka saker och formulera mig på. Calle, tack för

alla intensiva diskussioner och din röntgenblick som gör att du hittar artiklar i mina

utkast. Kurt, tack för att jag hann lära känna och inspireras av dig. Jag skulle även

vilja tacka min biträdande reservhandledare och tillika rumskamrat, Linda. Tack för

din tillgänglighet (du hade ju i och för sig inte mycket val…), ditt tålamod och den

klarhet du tillfogade alla mina förvirrade utkast, ideer och manuskript. Tack också

Pär för alla tips och diskussioner, även om alla inte har handlat om

forskningsrelaterade spörsmål.

Jag skulle även vilja tacka alla på miljökemi. Om man går med ett leende till jobbet,

diskuterar jonkällor och retentionstider över kaffet, kastar Tenaxrör på ballonger på

lunchen och övar på att sjunga konstiga visor på kvällarna finns det mycket som tyder

på att man jobbar på en trevlig och kreativ arbetsplats. Tack för All Hjälp! Utan er

alla hade detta arbete varit betydligt tunnare och mina arbetsdagar betydligt tråkigare!

Tack Albert Crenshaw (LA-Write Now) för dina utmärkta språkgranskningar och

roliga diskussioner.

Jag skulle även vilja tacka Arbetslivsinstitutet, Civilingenjörsförbundet,

Kempestiftelserna, Knut och Alice Wallenbergstiftelsen och Ångpanne Föreningen

för olika grad av finansiellt stöd.

Mina kompisar, i exil och här i Umeå, jag vet var ni bor…

Tisdagsgänget (i dess absolut vidaste bemärkelse) utan vars hjälp och inflytande detta

arbete hade kunnat slutföras mycket tidigare. Tack för all visdom, kreativitet och

inlevelse som jag utsatts för och som jag aldrig kommer att bli av med. För att

- 27 -

missbruka Bruce's text "I learned more from a 7 h tuseday evening than I ever did in

school…"

Min släkt som nu är spridd över större delen av landet, jag tänker på er. Hoppas att vi

ses snart igen på födelsedagar, grillkvällar och gåsamiddagar.

Mamma och pappa, tack för att ni gjort mig till den jag är. Tack för allt stöd och all

livsglädje. Pappa, jag saknar dig.

Jag skulle även vilja tacka min fru, Hanna, tack för att du har stöttat mig och alltid

finns där innan jag ens vet att jag behöver det och sist och minst Didrik, tack för att

du finns.

13. REFERENCES

1. Gummere, R. M. In Ad Lucilium Epistolae Morales III. 1971. Heinemann, London.

2. Brimblecombe, P. The big smoke. 1987. Routledge, London. 3. Ramazzini, B. Diseases of workers. 1983. The Classics of Medicine Library,

Gryphon Editions, New York. 4. Weschler, C. J.; Shields, H. C. Potential reactions among indoor pollutants. Atmos.

Environ. 1997, 31, 3487-3495. 5. Wolkoff, P.; Clusen, P.; Jensen, B.; Nielsen, G.; Wilkins, C. Are we measuring the

relevant indoor pollutants? Indoor Air 1997, 7, 92-106. 6. Spengler, J. D.; Sexton, K. Indoor air pollution: A public health perspective.

Science 1983, 221, 9-17. 7. Smith, K. R. Biofuels, air pollution and health. A global review. 1987. Plenum

Press, New York. 8. WHO. Air quality guidelines. 1999. WHO, Geneva. 9. Bruce, N.; Perez-Padilla, R.; Albalak, R. Indoor air pollution in developing

countries: a major environmental and public health challenge for the new millenium. Bull. World. Health. Organ. 2000, 78, 1078-1092.

10. WHO. World health report 2002, reducing risks, promoting healthy life. 2002. WHO, Geneva.

11. Wells, C. Diseases of the maxillary sinus in antiquity. Med. Biol. Illus. 1977, 27, 173-178.

12. Stolwijk, J. A. Risk assessment of acute health and comfort effects of indoor air pollution. Ann. N. Y. Acad. Sci. 1992, 641, 56-62.

13. WHO. Indoor air pollutants: exposure and health effects. EURO Rep. Stud. 1983, 78, 1-42.

14. Jones, A. P. Asthma and domestic air quality. Soc. Sci. Med. 1998, 47, 755-764.

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15. Horvath, E. P. Building-related illness and sick building syndrome: from the specific to the vague. Cleve. Clin. J. Med. 1997, 64, 303-309.

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18. Mendell, M. J.; Smith, A. H. Consistent pattern of elevated symptoms in air.conditioned office buildings: A reanalysis of epidemiologic studies. Am. J. Public. Health. 1990, 80, 1193-1199.

19. Apter, A.; Bracker, A.; Hodgson, M.; Sidman, J.; Leung, W. -Y. Epidemiology of the sick building syndrome. J. Allergy. Clin. Immunol. 1994, 94, 277-288.

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volatile organic compounds. Environ. Int. 1986, 12, 167-175. 22. Brown, S. K.; Sim, M. R.; Abramson, M. J.; Gray, C. N. Concentrations of

Volatile Organic Compounds in indoor Air- A Review. Indoor Air 1994, 4, 123-134.

23. Pommer, L.; Fick, J.; Andersson, B.; Sundell, J.; Nilsson, C.; Sjöström, M.; Stenberg, B. Class separation of buildings with high and low prevalence of SBS by principal Component Analysis. Indoor Air 2003, In press.

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25. Seppänen, O. A.; Fisk, W. J.; Mendell, M. J. Association of ventilation rates and CO2 concentrations with health and other responses in commercial and institutional buildings. Indoor Air 1999, 9, 226-252.

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