Annals of Occupational Hygiene Advance Access originally published online on October 5, 2007
Annals of Occupational Hygiene 2007 51(8):693-701; doi:10.1093/annhyg/mem046
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Exposure to Particles, Elemental Carbon and Nitrogen Dioxide in Workers Exposed to Motor Exhaust
1 Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden
2 Department of Occupational and Environmental Health, Stockholm Centre for Public Health, Stockholm, Sweden
* Author to whom correspondence should be addressed. Tel: +46-8-737-36-83; fax: +46-8-33-43-33; e-mail: marie.lewne{at}sll.se
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
Objectives: The main aim of this study was to investigate the personal exposure to diesel and petrol exhaust fumes in occupations when exposure is prevalent and/or high. We also investigated the correlation between the five particle fractions [particles with an aerodynamic diameter <1 µm (PM1), particles with an aerodynamic diameter <2.5 µm (PM2.5), particles in size 0.1–10 µm, elemental carbon (EC) and total carbon (TC)] and nitrogen dioxide (NO2), in the various occupational environments.
Methods: Seventy-one workers were included in the study. They were subdivided into seven groups depending on working area, working indoors, out of doors or in vehicles and type of exposure (diesel or petrol exhaust). Personal measurements were performed during 3 days per worker. We used five indicators of the particle fraction: PM1, PM2.5, particle measured with a real-time monitoring instrument for particles in sizes 0.1 and 10 µm (DataRAM), EC and TC. We used NO2 as an indicator of the gas phase.
Results: Tunnel construction workers showed the highest levels of exposure for all indicators, followed by diesel-exposed garage workers. For the other five groups, the levels were statistically significantly lower, and the differences between the groups were small. The full-shift geometric average of PM1 varied between 119 µg m–3 (tunnel construction workers) and 11 µg m–3 (taxi drivers). For PM2.5, the levels varied between 231 µg m–3 (tunnel construction workers) and 16 µg m–3 (bus and lorry drivers). For the measurements with the real-time monitoring instrument DataRAM, the levels varied between 398 µg m–3 (tunnel construction workers) and 14 µg m–3 (taxi drivers). For EC, the levels varied between 87 µg m–3 (tunnel construction workers) and 4 µg m–3 (other outdoor workers exposed to diesel exhaust), and for TC, the levels varied between 191 µg m–3 (tunnel construction workers) and 10 µg m–3 (taxi drivers). Finally, for NO2, the levels varied between 350 µg m–3 (tunnel construction workers) and 32 µg m–3 (other outdoor workers exposed to diesel exhaust). For the indoor workers exposed to diesel exhaust fumes only, all the indicators correlated comparatively well and statistically significantly to each other (r2 = 0.44–0.89). For the other groups, correlations were lower and showed no consistent pattern.
Conclusions: The tunnel construction workers had exposure levels for all indicator substances that were considerably and significantly higher than for the other groups. The NO2 levels were higher for indoor workers exposed to diesel exhaust than for all other groups (except tunnel construction workers). All particle fractions, as well as NO2 correlated well in occupations with indoor exposure to diesel exhaust.
Keywords: diesel exhaust • indicator substances • measurements • NO2 • occupational exposure • particles • petrol exhaust
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
Three million workers in Europe are exposed to diesel exhaust fumes at work, 81 000 of them in Sweden (Kauppinen et al., 2000). The risk of cancer and respiratory and cardiovascular diseases is related to exposure to combustion products (Boffetta et al., 1997; Pope et al., 2002). The International Agency for Research on Cancer has classified diesel exhaust as probably carcinogenic to humans and petrol exhaust as possibly carcinogenic to humans (IARC, 1989).
Motor exhaust is a complex mixture of gases and particulate matter. The particles consist of a core of elemental carbon (EC) to which organic compounds formed during the combustion are adsorbed. Traces of metal compounds and sulphates are also present in the particulate fraction. At formation, the particles are very small, with an aerodynamic diameter of less than 0.1 µm, but they aggregate and form larger particles. Most of these are still smaller than 1 µm. Diesel-powered vehicles produce 
2 to 40 times more particles than petrol-powered vehicles depending on the type of diesel fuel and the detailed construction of the engine (IARC, 1989).
The gas fraction is a mixture of thousands of chemical compounds. Most important from a toxicological point of view are organic compounds such as aromatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), aldehydes and nitrogen oxides. Exhaust fumes from petrol-powered vehicles without catalytic converters contain considerably more carbon monoxide (CO) than exhaust fumes from diesel vehicles (IARC, 1989; WHO, 1996).
Most studies on conditions of exposure have concentrated on rather uncommon occupations involving high exposure to diesel exhaust (Gamble et al., 1987; Whittaker et al., 1999; Groves and Cain, 2000), and there have been few studies on exposure in common occupations with lower levels of exhaust. Little is known about exposure in common occupations such as professional drivers or car mechanics.
Due to the complexity of the content of exhaust fumes, indicator substances are used to quantify the exposure. Nitrogen dioxide (NO2) has commonly been used as an indicator for diesel exhaust (Woskie et al., 1989; Zagury et al., 2000). EC was proposed at the beginning of the 1990s in an attempt to find a more specific indicator of diesel exhaust (Zaebst et al., 1991; Verma et al., 2003). Particle matter (Guillemin et al., 1992; Riediker et al., 2003), PAH (Guillemin et al., 1992; Kuusimaki et al., 2003) and other organic hydrocarbons (Jo and Song, 2001) have also been measured in workers exposed to diesel exhaust.
Before the introduction of catalytic exhaust emission control, CO was a major toxic component of exhaust from petrol-powered engines and was used as an indicator of exposure (Limasset et al., 1993; Riediker et al., 2003; Han et al., 2005).
There is a lack of systematic investigations of how different indicator substances behave when used as indicators of diesel and petrol exhaust.
|
AIMS |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
The aim of this study was to investigate the personal exposure to motor exhaust in occupations where such exposure is common or high. We also investigated the correlation between the indicators in various occupational environments. The study was initiated in order to update two population-based case–control studies—lung cancer (Gustavsson et al., 2000) and myocardial infarction (Gustavsson et al., 2001)—with quantitative data on the personal exposure to motor exhaust.
|
STUDY SUBJECTS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
Seven groups of occupations, with 71 workers altogether, were defined depending on the type of fuel (diesel or petrol) and workplace (indoors, out of doors or in a vehicle).
Group A (tunnel construction workers) included six workers engaged in the construction of a road tunnel in Stockholm. They worked with various installation tasks, using diesel-powered machines and vehicles. Since the tunnel construction was in the final stage, there was no blasting in progress in any part of the tunnel.
Group B (garage workers—diesel) included 20 workers. Fifteen of them worked as lorry or bus mechanics, three worked on other tasks in a bus garage and two worked for the Swedish Vehicle Inspection Company inspecting lorries and buses.
Group C (garage workers—petrol) included six private car mechanics and two parking garage attendants. Since 95% of private cars in Sweden use petrol, we classified them as being exposed to petrol exhaust.
Group D (construction machine operators) included 11 workers. They worked inside or nearby diesel-fuelled construction machines such as excavators, gulley emptiers, etc. The exhaust fumes originated mainly from their own vehicle, but nearby traffic may have contributed.
Group E (other outdoor workers exposed to diesel exhaust) included 12 workers working in or around diesel-fuelled trucks, tractors in agriculture, shunting engines, etc. They all worked in areas with no other traffic close by.
Group F (bus and lorry drivers) included four bus drivers and six lorry drivers. Two of the bus drivers worked in the city of Stockholm (using ethanol-fuelled buses) and the other two worked in a suburb (on diesel-fuelled buses). All lorry drivers drove in and around Stockholm city, using diesel fuel.
Group G (taxi drivers) included four taxi drivers driving in and around the city of Stockholm. Three of the taxis used diesel fuel and one used petrol.
Of the 71 workers, 68 were men and three were women. All were non-smokers, and smoking was not allowed indoors at any of the workplaces or in any of the vehicles.
We used five exposure indicators for the particle phase of the exhaust: particles with an aerodynamic diameter of <1 µm (PM1), particles with an aerodynamic diameter of <2.5 µm (PM2.5) and particles of sizes between 0.1 and 10 µm (measured with the real-time monitoring instrument DataRAM). We also sampled and analysed EC and organic carbon (OC). Elemental and OCs together represent the total carbon (TC). We used NO2 as an indicator of the gas phase of the exhaust. We used pump units and gravimetric determination for PM1 and PM2.5, a real-time monitoring instrument for particles in size 0.1–10 µm and pump units and chemical analysis for the EC and TC determination. For NO2, we used diffusive samplers. Table 1 gives information about the methods, number of measurements, measuring time and limit of detection for each indicator.
|
Measurements were done between October 2002 and June 2004, the aim being that they should be representative of normal working conditions. All measurements were based on personal sampling. None of the workers used respiratory protection during work. Three full shifts were measured for all workers. PM1 and EC were measured during 2 days each and NO2 was measured all 3 days. PM2.5 and DataRAM were measured during 1 day. Thus, each day, two different particle fractions and NO2 were measured. The order of the particle fractions was randomly selected.
Statistical methods
Histograms of the parameters measured showed lognormal distributions both for particle fractions and NO2. Thus, we used logarithmically transformed values for all statistical calculations and expressed our results as geometric mean and geometric standard deviation. We used SPSS version 13.0 for Windows for all statistical calculations. Differences between means were tested by t-test for independent samples, applied to the log-transformed values. A P-value <0.05 was considered statistically significant (two-tailed tests were used).
Pearson's correlation coefficient was used to investigate the correlations between the exposure indicators. Two-tailed tests were used.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
The tunnel construction workers (Group A) showed considerably higher levels of exposure for all indicators than the other groups (Table 2 and Fig. 1). The exposure levels were statistically significantly higher than in the other groups for all six indicators (P < 0.01) (Table 3).
|
|
|
For the other six groups, the levels were lower and the ranking order between them depended on which indicator was used. In Table 3, we have illustrated which of the groups having indicators statistical significant different from others.
The indoor workers in Group B (garage workers—diesel) had statistically higher levels of NO2 than Groups C–G, and for some of the other indicators, both Group B and Group C (garage workers—petrol) had higher levels than the outdoor workers in Group E (other outdoor workers exposed to diesel exhaust) and the drivers in Groups F and G.
Both groups with outdoor exposed workers (Group D = construction machine operators and Group E = other outdoor workers exposed to diesel exhaust) had similar exposure levels except for particles in size 0.1–10 µm (DataRAM), for which Group D had the higher levels.
Both groups of drivers had lower levels than the others for most of the indicators. But for NO2, Group F (bus and lorry drivers) had higher levels than Group E (other outdoor workers exposed to diesel exhaust). Between the drivers themselves, only the particles in size 0.1–10 µm (DataRAM) differed significantly, with higher levels for the bus and lorry drivers (Group F) compared to taxi drivers (Group G).
Correlations between indicators were investigated among indoor exposure to diesel exhaust (Groups A and B), in order to obtain a group with homogenous exposure source (Table 4).
|
For this pooled Group (A + B), all correlations were statistically significant, most of them with P < 0.01. Correlations were also studied for the other groups but we did not find any uniform pattern for the correlations, except for EC and TC which correlated strongly (P < 0.01) as were expected.
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
This is a relatively large survey of exposure to motor exhaust covering several occupations and involving 213 full-shift samples and 500 sampling results. One advantage of our study is the use of five different particle indicators and NO2 as an indicator for the gas phase. A weakness is that the number of samples per occupational group was low due to restricted resources.
The tunnel construction workers (Group A) had the highest exposure to all indicators used in the study. This was to be expected, since this tunnel was an enclosed area with insufficient ventilation and many diesel-driven machines working under high load. During sampling, there was some drilling in progress in a nearby area, which may have had an influence on the high levels of large particles detected by the DataRAM and PM2.5. However, all the contributions to EC levels were from the diesel exhaust, since there were no other sources of EC nor was there any source of NO2 other than the diesel-powered machines, since the blasting was finished months before.
The other groups showed no consistent ranking order, but the indoor workers had higher levels of exposure than outdoor workers for most of the indicators. For PM1, there was, as expected, a higher level of exposure for indoor garage workers (Groups B and C) than for drivers (Groups F and G). Rather unexpected, there were no differences between the PM1 levels for the indoor (Groups B and C) and the outdoor groups (Groups D and E).
For Group B (garage workers—diesel), the EC levels were not significantly higher compared to Groups C (garage workers—petrol), D (construction machine operators) and the drivers in Groups F and G, which we had expected. Only compared to Group E (other outdoor workers exposed to diesel exhaust), the EC levels were higher for both groups of indoor workers (Groups B and C).
We had expected higher levels of EC in the diesel garage workers (Group B) than in the petrol garage workers (Group C), since more EC is emitted from diesel vehicles than from petrol vehicles (Zaebst et al., 1991). But the levels were quite similar, actually showing somewhat higher levels for the petrol garage workers. This was probably due to chance because many samples were close to or below the detection limit.
Regarding the indoor workers, NO2 levels were higher for the diesel garage workers than for the petrol garage workers. This was to be expected since diesel exhaust gives higher exposure to NO2 than petrol exhaust (IARC, 1989). Gas heaters or gas stoves, which could influence the levels of NO2, were not in use in any of the working places.
NO2 levels for outdoor workers and drivers are influenced both by exhaust fumes from their own vehicles and by the urban background levels at the work site. For bus/lorry drivers (Group F), the exposure levels of NO2 were higher than for Group E (other outdoor workers exposed to diesel exhaust). This was probably caused by a higher contribution of NO2 from surrounding traffic for the drivers than for the outdoor workers in Group E.
In both groups of outdoor workers (Groups D and E), some of the workers spend most time inside their machines whereas others were out of doors. When analysing the individuals, we could not discern any systematic differences between the machine drivers and the others.
There are a large number of indicators available for measuring motor exhaust. Methods for sampling and analysis may also differ. This makes it problematic to compare findings from different studies.
In general, the particle and NO2 levels found in this study were of the same magnitude as for similar occupational groups in other studies, although there was a large variation and there have been studies showing both higher and lower levels of different particle fractions. In Table 5, we have summarized results from other studies measuring same indicators for motor exhaust exposure, in comparable occupations.
|
We have not found any studies using PM1 as an indicator of occupational exposure to motor exhaust. For PM2.5, there are a few studies and for EC and NO2, there are a lot of studies with comparable occupations. For PM2.5, the level in Peru is 10-fold the level in Sweden, but the vehicles in Peru are older and without exhaust emission control, so the environments are quite different. The levels for patrol cars in US were more similar with our results.
The EC levels in our study varied from 4–12 µg m–3 for all groups except the tunnel construction workers who had markedly higher exposure levels (87 µg m–3). For indoor diesel workers, our result of 11 µg m–3 EC is in accordance with similar environments in the North America, while somewhat higher levels have been reported from Europe. For drivers, the levels seemed to be somewhat lower in North America and somewhat higher in Europe compared to our results.
NO2 average levels varied between 32 and 350 µg m–3 in this study. Thus, the NO2 levels found in the present study appear to be lower than for most comparable occupations in other countries. One explanation could be the use of another diesel fuel in Sweden (Swedish MK1-fuel), a low-sulphur diesel giving 12 to 13% lower emission of nitrogen oxides and particles than conventional European diesel fuel (Westerholm et al., 2001). In addition, the share of diesel-driven private cars are low in Sweden, 5%, compared to many other countries, which probably also give lower level of NO2 in surroundings. Other explanations for the differences in NO2 levels between our study and others could be different analytical methods. Equipments using chemical cells have been used in some studies. From our experience, this method is not sensitive enough measuring NO2 as indicator for motor exhaust. Even different demands for exhaust emission control and ventilation indoors etc. in different counties may have influenced the levels. For drivers, and other outdoor workers, also the urban background levels in different areas are of importance for the workers' exposure.
As appears from Table 4, the correlations between the indicators were statistically significant between all indicators for indoor workers, working with diesel vehicles. For all other groups, the correlations were lower, except for EC and TC, and without any consistent pattern.
A study of diesel forklift truck drivers in the UK reported no clear relationship between EC and OC, nor between respirable dust and EC or OC (Groves and Cain, 2000). In different occupations in a Canadian railway company, no correlations were found between respirable combustible dust and NO2 or between EC and NO2 (Verma et al., 1999). On the other hand, we have found one study reporting a good correlation between different indicators. In distribution depots in the UK, where diesel-powered forklift trucks were in use, EC/OC/TC, PAH, respirable dust and ultrafine particles were all correlated significantly to each other with correlation coefficients between 0.29 and 0.97 (Wheatley and Sadhra, 2004).
In occupational hygiene, particles generally are detected as inhalable or respirable dust, but since motor exhaust particles are small, most of them <1 µm, these methods are not relevant for detecting motor exhaust exposure. Instead we have detected particles as PM1 and PM2.5 (particles in size <1 and <2.5 µm, respectively). These particle sizes are commonly measured in environmental studies. The particles measured with the real-time monitoring instrument (DataRAM), detecting particles in size 0.1–10 µm, probably originate not only from motor exhaust but still we found the information about the fluctuation of the dust levels during the day important.
For EC/TC, unfortunately, the methods for analysis (German reference method BG, ZH 1/120.44-2) were not sensitive enough for some of the environments. Even though we measured during two working days, 20% of the measurements were below the detection limit. Then, the group means levels for EC/TC may be less reliable, since many values also were near the detection limit.
We did not give priority to measure CO in this study. In Sweden, with catalytic exhaust emission control, the levels of CO are low and equipment for personal monitoring that is sensitive enough is not available.
Of the six exposure indicators studied, NO2, PM1 and EC were judged a priori to be relatively specific indicators of motor exhaust. On the basis of the present results, none can be safely judged to be better than any other, but one observation may be noted. For indoor workers with diesel vehicles or machines as the primary source of exposure, there was a fairly good correlation between PM1, EC and NO2 and any of them could serve as an indicator for comparison of levels between workers or occupations.
Thus, for assessment of motor exhaust exposure in other situations, there is no obvious best indicator. However, NO2 is simpler to measure than the others. For PM1, at least two full-shift measurements with pump units are needed. For EC, and with the analytical method used in this study, even more than two full shifts must bee used. Consequently, the measurements are costly and time consuming. It should be kept in mind, however, that NO2 is a secondary constituent of the exhaust gases and that the transformation from NO to NO2 depends on the levels of ozone and other photochemical oxidants. In closed areas, as in the tunnel, the transformation to NO2 is slower due to low levels of ozone.
|
CONCLUSIONS |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
The group ‘tunnel construction workers’ had exposure levels of all indicator substances that were considerably and significantly higher than for the other groups. The differences between the six other groups of motor exhaust-exposed workers were smaller. However, the NO2 levels were higher for workers exposed to diesel exhaust than for those exposed to petrol exhaust and higher for indoor work than for outdoor work with exposure to diesel fumes.
For occupations with indoor exposure to diesel exhaust, PM1, EC and NO2 levels, as well as the other particle fractions, correlated well to each other and any of them could be used as an indicator for diesel exposure. For the other groups, the correlations between the indicators were low and no single indicator can be used alone to assess the exposure.
|
FUNDING |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
FAS (2001-2431, the Swedish Council for Working Life and Social Research).
|
ACKNOWLEDGEMENTS |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
The authors wish to thank Eva Lenell for her contribution with the measurements, Magnus Alderling for statistical support and all the study subjects for carrying the equipment for 3 days.
Received February 13, 2007; in final form June 15, 2007
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONAIMSSTUDY SUBJECTS AND METHODSRESULTSDISCUSSIONCONCLUSIONSFUNDINGACKNOWLEDGEMENTSREFERENCES |
|---|
Boffetta P, Cherrie J, Hughson G, et al. Cancer risk from diesel emissions exposure in central and eastern Europe: a feasibility study (2002) Institute HE. 59–78.
Boffetta P, Jourenkova N, Gustavsson P. Cancer risk from occupational and environmental exposure to polycyclic aromatic hydrocarbons. Cancer Causes Control (1997) 8:444–72.[CrossRef][Web of Science][Medline]
Ferm M, Rodhe H. Measurements of air concentrations of SO2, NO2 and NH3 at rural and remote sites in Asia. J Atmos Chem (1997) 27:17–29.[CrossRef]
Ferm M, Svanberg P-A. Cost-efficient techniques for urban and background measurements of SO2 and NO2. Atmos Environ (1998) 32:1377–81.
Gamble J, Jones W, Minshall S. Epidemiological-environmental study of diesel bus garage workers: acute effects of NO2 and respirable particulate on the respiratory system. Environ Res (1987) 42:201–14.[Medline]
Groves J, Cain JR. A survey of exposure to diesel engine exhaust emissions in the workplace. Ann Occup Hyg (2000) 44:435–47.
Guillemin MP, Herrera H, Huynh CK, et al. Occupational exposure of truck drivers to dust and polynuclear aromatic hydrocarbons: a pilot study in Geneva, Switzerland. Int Arch Occup Environ Health (1992) 63:439–47.[CrossRef][Web of Science][Medline]
Gustavsson P, Jakobsson R, Nyberg F, et al. Occupational exposure and lung cancer risk: a population-based case-referent study in Sweden. Am J Epidemiol (2000) 152:32–40.
Gustavsson P, Plato N, Hallqvist J, et al. A population-based case-referent study of myocardial infarction and occupational exposure to motor exhaust, other combustion products, organic solvents, lead, and dynamite. Stockholm Heart Epidemiology Program (SHEEP) Study Group. Epidemiology (2001) 12:222–8.[CrossRef][Web of Science][Medline]
Han X, Aguilar-Villalobos M, Allen J, et al. Traffic-related occupational exposures to PM2.5, CO, and VOCs in Trujillo, Peru. Int Arch Occup Environ Health (2005) 11:276–88.
IARC. Monographs on the evaluation of carcinogenic risk to humans. Diesel and gasoline engine exhausts and some nitroarenes (1989) Vol. 46. Lyon: International Agency for Research on Cancer, World Health Organisation.
Jo WK, Song KB. Exposure to volatile organic compounds for individuals with occupations associated with potential exposure to motor vehicle exhaust and/or gasoline vapor emissions. Sci Total Environ (2001) 269:25–37.[CrossRef][Medline]
Kauppinen T, Toikkanen J, Pedersen D, et al. Occupational exposure to carcinogens in the European Union. Occup Environ Med (2000) 57:10–8.
Kuusimaki L, Peltonen K, Mutanen P, et al. Analysis of particle and vapour phase PAHs from the personal air samples of bus garage workers exposed to diesel exhaust. Ann Occup Hyg (2003) 47:389–98.
Lewné M, Nise G, Lind ML, et al. Exposure to particles and nitrogen dioxide among taxi, bus and lorry drivers. Int Arch Occup Environ Health (2006) 79:220–6.[CrossRef][Web of Science][Medline]
Limasset JC, Diebold F, Hubert G. Exposure of urban bus drivers to traffic pollution. Sci Total Environ (1993) 134:39–49.[CrossRef][Medline]
Pope CA 3rd, Burnett RT, Thun MJ, et al. Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA (2002) 287:1132–41.
Riediker M, Williams R, Devlin R, et al. Exposure to particulate matter, volatile organic compounds, and other air pollutants inside patrol cars. Environ Sci Technol (2003) 37:2084–93.[Medline]
Sauvain JJ, Vu Duc T, Guillemin M. Exposure to carcinogenic polycyclic aromatic compounds and health risk assessment for diesel-exhaust exposed workers. Int Arch Occup Environ Health (2003) 76:443–55.[CrossRef][Web of Science][Medline]
Seshagiri B, Burton S. Occupational exposure to diesel exhaust in the Canadian federal jurisdiction. AIHA J (Fairfax, VA) (2003) 64:338–45.
Son B, Yang W, Breysse P, et al. Estimation of occupational and nonoccupational nitrogen dioxide exposure for Korean taxi drivers using a microenvironmental model. Environ Res (2004) 94:291–6.[Medline]
Verma DK, Finkelstein MM, Kurtz L, et al. Diesel exhaust exposure in the Canadian railroad work environment. Appl Occup Environ Hyg (2003) 18:25–34.[CrossRef][Medline]
Verma DK, Shaw L, Julian J, et al. A comparison of sampling and analytical methods for assessing occupational exposure to diesel exhaust in a railroad work environment. Appl Occup Environ Hyg (1999) 14:701–14.[CrossRef][Medline]
Westerholm R, Christensen A, Tornqvist M, et al. Comparison of exhaust emissions from Swedish environmental classified diesel fuel (MK1) and European Program on Emissions, Fuels and Engine Technologies (EPEFE) reference fuel: a chemical and biological characterization, with viewpoints on cancer risk. Environ Sci Technol (2001) 35:1748–54.[Medline]
Wheatley AD, Sadhra S. Occupational exposure to diesel exhaust fumes. Ann Occup Hyg (2004) 48:369–76.
Whittaker LS, MacIntosh DL, Williams PL. Employee exposure to diesel exhaust in the electric utility industry. Am Ind Hyg Assoc J (1999) 60:635–40.[Web of Science][Medline]
WHO. Diesel fuel and exhaust emissions. In: Environmental Health Criteria 171 (1996) Geneva: World Health Organization.
Woskie SR, Hammond SK, Smith TJ, et al. Current nitrogen dioxide exposures among railroad workers. Am Ind Hyg Assoc J (1989) 50:346–53.[Web of Science][Medline]
Zaebst DD, Clapp DE, Blade LM, et al. Quantitative determination of trucking industry workers' exposures to diesel exhaust particles. Am Ind Hyg Assoc J (1991) 52:529–41.[Web of Science][Medline]
Zagury E, Le Moullec Y, Momas I. Exposure of Paris taxi drivers to automobile air pollutants within their vehicles. Occup Environ Med (2000) 57:406–10.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||