BACKGROUND: An increased risk of lung cancers among asphalt workers has been suggested in epidemiological studies based on large scale statistical analyses. METHODS: In a multi-country study of 29,820 male workers employed in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers and 17,757 other workers from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality that was documented from 1953-2000. Exposures to bitumen fume, coal tar, 4-6 ring polycyclic aromatic hydrocarbons, organic vapor, diesel exhaust, asbestos, and silica dust were assessed via a job-exposure matrix. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates, as well as relative risks (RRs) based on Poisson regression models were calculated. RESULTS: The SMR of lung cancer among workers exposed to bitumen fume (1.08, 95% CI 0.99-1.18) was comparable to that of non-exposed workers (SMR 1.05, 95% CI 0.92-1.19). In a sub-cohort of bitumen-exposed workers without exposure to coal tar, the SMR of lung cancer was 1.23 (95% CI 1.02-1.48). The analysis based on the semi-quantitative, matrix-based exposures in the whole cohort did not suggest an increased lung cancer risk following exposure to bitumen fume. However, in an analysis restricted to road pavers, based on quantitative estimate of bitumen fume exposure, a dose-response was suggested for average level of exposure, applying a 15-year lag, which was marginally reduced after adjustment for co-exposure to coal tar. The results for cancer of the head and neck were similar to those of lung cancer, although they were based on a smaller number of deaths. There was no clear suggestion of an association with bitumen fume for any other neoplasm. CONCLUSIONS: The results of the analysis by bitumen fume exposure do not allow us to conclude on the presence or absence of a causal link between exposure to bitumen fume and risk of cancer of the lung and the head and neck.
BACKGROUND: Inhalation of bitumen fumes is potentially carcinogenic to humans. METHODS: We conducted a study of 29,820 male workers exposed to bitumen in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers unexposed to bitumen, and 17,757 workers not classifiable as bitumen workers, from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality follow-up during 1953-2000. We calculated standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates. Poisson regression analyses compared mortality of bitumen workers to that of building or ground construction workers. RESULTS: The overall mortality was below expectation in the total cohort (SMR 0.92, 95% CI 0.90-0.94) and in each group of workers. The SMR of lung cancer was higher among bitumen workers (1.17, 95% CI 1.04-1.30) than among workers in ground and building construction (SMR 1.01, 95% CI 0.89-1.15). In the internal comparison, the relative risk (RR) of lung cancer mortality among bitumen workers was 1.09 (95% CI 0.89-1.34). The results of cancer of the head and neck were similar to those of lung cancer, based on a smaller number of deaths. There was no suggestion of an association between employment in bitumen jobs and other cancers. CONCLUSIONS: European workers employed in road paving, asphalt mixing and other jobs entailing exposure to bitumen fume might have experienced a small increase in lung cancer mortality risk, compared to workers in ground and building construction. However, exposure assessment was limited and confounding from exposure to carcinogens in other industries, tobacco smoking, and other lifestyle factors cannot be ruled out.
SYNERGY is a large pooled analysis of case-control studies on the joint effects of occupational carcinogens and smoking in the development of lung cancer. A quantitative job-exposure matrix (JEM) will be developed to assign exposures to five major lung carcinogens [asbestos, chromium, nickel, polycyclic aromatic hydrocarbons (PAH), and respirable crystalline silica (RCS)]. We assembled an exposure database, called ExpoSYN, to enable such a quantitative exposure assessment.
Existing exposure databases were identified and European and Canadian research institutes were approached to identify pertinent exposure measurement data. Results of individual air measurements were entered anonymized according to a standardized protocol.
The ExpoSYN database currently includes 356?551 measurements from 19 countries. In total, 140 666 personal and 215?885 stationary data points were available. Measurements were distributed over the five agents as follows: RCS (42%), asbestos (20%), chromium (16%), nickel (15%), and PAH (7%). The measurement data cover the time period from 1951 to present. However, only a small portion of measurements (1.4%) were performed prior to 1975. The major contributing countries for personal measurements were Germany (32%), UK (22%), France (14%), and Norway and Canada (both 11%).
ExpoSYN is a unique occupational exposure database with measurements from 18 European countries and Canada covering a time period of >50 years. This database will be used to develop a country-, job-, and time period-specific quantitative JEM. This JEM will enable data-driven quantitative exposure assessment in a multinational pooled analysis of community-based lung cancer case-control studies.
BACKGROUND: An exposure matrix (EM) for known and suspected carcinogens was required for a multicenter international cohort study of cancer risk and bitumen among asphalt workers. METHODS: Production characteristics in companies enrolled in the study were ascertained through use of a company questionnaire (CQ). Exposures to coal tar, bitumen fume, organic vapor, polycyclic aromatic hydrocarbons, diesel fume, silica, and asbestos were assessed semi-quantitatively using information from CQs, expert judgment, and statistical models. Exposures of road paving workers to bitumen fume, organic vapor, and benzo(a)pyrene were estimated quantitatively by applying regression models, based on monitoring data, to exposure scenarios identified by the CQs. RESULTS: Exposures estimates were derived for 217 companies enrolled in the cohort, plus the Swedish asphalt paving industry in general. Most companies were engaged in road paving and asphalt mixing, but some also participated in general construction and roofing. Coal tar use was most common in Denmark and The Netherlands, but the practice is now obsolete. Quantitative estimates of exposure to bitumen fume, organic vapor, and benzo(a)pyrene for pavers, and semi-quantitative estimates of exposure to these agents among all subjects were strongly correlated. Semi-quantitative estimates of exposure to bitumen fume and coal tar exposures were only moderately correlated. EM assessed non-monotonic historical decrease in exposures to all agents assessed except silica and diesel exhaust. CONCLUSIONS: We produced a data-driven EM using methodology that can be adapted for other multicenter studies.
Diesel motor exhaust is classified by the International Agency for Research on Cancer as probably carcinogenic to humans. The epidemiologic evidence is evaluated as limited because most studies lack adequate control for potential confounders and only a few studies have reported on exposure-response relationships.
Investigate lung cancer risk associated with occupational exposure to diesel motor exhaust, while controlling for potential confounders.
The SYNERGY project pooled information on lifetime work histories and tobacco smoking from 13,304 cases and 16,282 controls from 11 case-control studies conducted in Europe and Canada. A general population job exposure matrix based on ISCO-68 occupational codes, assigning no, low, or high exposure to diesel motor exhaust, was applied to determine level of exposure.
Odds ratios of lung cancer and 95% confidence intervals were estimated by unconditional logistic regression, adjusted for age, sex, study, ever-employment in an occupation with established lung cancer risk, cigarette pack-years, and time-since-quitting smoking. Cumulative diesel exposure was associated with an increased lung cancer risk highest quartile versus unexposed (odds ratio 1.31; 95% confidence interval, 1.19-1.43), and a significant exposure-response relationship (P value
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Work in the asphalt industry has been associated with nonmalignant respiratory morbidity and mortality, but the evidence is not consistent. A historical cohort of asphalt workers included 58,862 men (911,209 person-years) first employed between 1913 and 1999 in companies applying and mixing asphalt in Denmark, Finland, France, Germany, Israel, the Netherlands, and Norway. The relations between mortality from nonmalignant respiratory diseases (including the obstructive lung diseases: chronic bronchitis, emphysema, and asthma) and specific chemical agents and mixtures were evaluated using a study-specific exposure matrix. Mortality from obstructive lung diseases was associated with the estimated cumulative and average exposures to polycyclic aromatic hydrocarbons and coal tar (p values of the test for linear trend = 0.06 and 0.01, respectively). The positive association between bitumen fume exposure and mortality from obstructive lung diseases was weak and not statistically significant; confounding by simultaneous exposure to coal tar could not be excluded. The authors lacked data on smoking and full occupational histories. In conclusion, exposures to polycyclic aromatic hydrocarbons, originating from coal tar and possibly from bitumen fume, may have contributed to mortality from obstructive lung diseases among asphalt workers, but confounding and bias cannot be ruled out as an explanation for the observed associations.
Organic dust is a complex mixture of particulate matter from microbial, plant or animal origin. Occupations with exposure to animal products have been associated with an increased lung cancer risk, while exposure to microbial components (eg, endotoxin) has been associated with a decreased risk. To date there has not been a comprehensive evaluation of the possible association between occupational organic dust exposure (and its specific constituents) and lung cancer risk in the general population.
The SYNERGY project has pooled information on lifetime working and smoking from 13 300 lung cancer cases and 16 273 controls from 11 case-control studies conducted in Europe and Canada. A newly developed general population job-exposure matrix (assigning no, low or high exposure to organic dust, endotoxin, and contact with animals or fresh animal products) was applied to determine level of exposure. ORs for lung cancer were estimated by logistic regression, adjusted for age, sex, study, cigarette pack-years, time since quitting smoking, and ever employment in occupations with established lung cancer risk.
Occupational organic dust exposure was associated with increased lung cancer risk. The second to the fourth quartile of cumulative exposure showed significant risk estimates ranging from 1.12 to 1.24 in a dose-dependent manner (p
We describe the elaboration and sensitivity analyses of a quantitative job-exposure matrix (SYN-JEM) for respirable crystalline silica (RCS). The aim was to gain insight into the robustness of the SYN-JEM RCS estimates based on critical decisions taken in the elaboration process.
SYN-JEM for RCS exposure consists of three axes (job, region, and year) based on estimates derived from a previously developed statistical model. To elaborate SYN-JEM, several decisions were taken: i.e. the application of (i) a single time trend; (ii) region-specific adjustments in RCS exposure; and (iii) a prior job-specific exposure level (by the semi-quantitative DOM-JEM), with an override of 0 mg/m(3) for jobs a priori defined as non-exposed. Furthermore, we assumed that exposure levels reached a ceiling in 1960 and remained constant prior to this date. We applied SYN-JEM to the occupational histories of subjects from a large international pooled community-based case-control study. Cumulative exposure levels derived with SYN-JEM were compared with those from alternative models, described by Pearson correlation ((Rp)) and differences in unit of exposure (mg/m(3)-year). Alternative models concerned changes in application of job- and region-specific estimates and exposure ceiling, and omitting the a priori exposure ranking.
Cumulative exposure levels for the study subjects ranged from 0.01 to 60 mg/m(3)-years, with a median of 1.76 mg/m(3)-years. Exposure levels derived from SYN-JEM and alternative models were overall highly correlated (R(p) > 0.90), although somewhat lower when omitting the region estimate ((Rp) = 0.80) or not taking into account the assigned semi-quantitative exposure level (R(p) = 0.65). Modification of the time trend (i.e. exposure ceiling at 1950 or 1970, or assuming a decline before 1960) caused the largest changes in absolute exposure levels (26-33% difference), but without changing the relative ranking ((Rp) = 0.99).
Exposure estimates derived from SYN-JEM appeared to be plausible compared with (historical) levels described in the literature. Decisions taken in the development of SYN-JEM did not critically change the cumulative exposure levels. The influence of region-specific estimates needs to be explored in future risk analyses.
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