Pooled exposure-response analyses and risk assessment for lung cancer in 10 cohorts of silica-exposed workers: an IARC multicentre study

OBJECTIVES

Silica is one of the most common occupational exposures worldwide. In 1997 the International Agency for Research on Cancer (IARC) classified inhaled crystalline silica as a human carcinogen (group 1), but acknowledged limitations in the epidemiologic data, including inconsistencies across studies and the lack of extensive exposure-response data. We have conducted a pooled exposure-response analysis of 10 silica-exposed cohorts to investigate lung cancer.

METHODS

The pooled cohort included 65,980 workers (44,160 miners, 21,820 nominees), and 1,072 lung cancer deaths (663 miners, 409 nonminers). Follow-up has been extended for five of these cohorts beyond published data. Quantitative exposure estimates by job and calendar time were adopted, modified, or developed to permit common analyses by respirable silica (mg/m3) across cohorts.

RESULTS

The log of cumulative exposure, with a 15-year lag, was a strong predictor of lung cancer (p = 0.0001), with consistency across studies (test for heterogeneity, p = 0.34). Results for the log of cumulative exposure were consistent between underground mines and other facilities. Categorical analyses by quintile of cumulative exposure resulted in a monotonic trend with odds ratios of 1.0. 1.0, 1.3, 1.5, 1.6. Analyses using a spline curve also showed a monotonic increase in risk with increasing exposure. The estimated excess lifetime risk (through age 75) of lung cancer for a worker exposed from age 20 to 65 at 0.1 mg/m3 respirable crystalline silica (the permissible level in many countries) was 1.1-1.7%, above background risks of 3-6%.

CONCLUSIONS

Our results support the decision by the IARC to classify inhaled silica in occupational settings as a carcinogen, and suggest that the current exposure limits in many countries may be inadequate. These data represent the first quantitative exposure-response analysis and risk assessment for silica using data from multiple studies.

Work-related symptoms in sewage treatment workers

The aim of this study was to investigate health symptoms in sewage treatment workers. A health questionnaire was distributed among 147 sewage treatment workers. Correlating symptoms were clustered using principal component analysis and the association with self-reported exposure was assessed by calculating prevalence odds ratios (OR). Endotoxin was measured in two treatment plants. Personal endotoxin exposure was low (<10 Endotoxin Units/m(3)). Factor analysis of 29 symptoms resulted in four clusters of highly correlating symptoms: 'flu-like symptoms'; 'higher airway symptoms'; 'lower airway symptoms'; and 'neurological symptoms'. These clusters were positively associated with working with sewage, but only significant for 'flu- like symptoms' (OR=5.0; 95%CI=1.4-17.6; p<0.05) and 'neurological symptoms' (OR=4.2; 95%CI=1.5-11.7; p<0.01). Chemical exposure was associated with 'neurological symptoms' (OR=8.4; 95%CI=1.1-65.7; p<0.05). The use of daily washed working clothes was negatively associated with 'flu-like symptoms' (OR=0.3; 95%CI=0.1-0.6; p<0.01). In conclusion, sewage treatment workers develop a large variety of work-related symptoms that are not likely caused by endotoxin exposure only. Good hygienic practice at the workplace may prevent some of these symptoms

Coffee consumption and bladder cancer in nonsmokers: a pooled analysis of case-control studies in European countries

BACKGROUND

Coffee consumption has been associated with an excess bladder cancer risk, but results from epidemiological studies are inconsistent. This association has been long debated, in part due to the potential confounding by smoking. We examined the risk associated with coffee consumption in nonsmokers in a pooled analysis of ten European bladder cancer case-control studies.

METHODS

The pooled data set comprises 564 cases and 2929 hospital or population controls who had never smoked. They were enrolled in ten studies conducted in Denmark, Germany, Greece, France, Italy and Spain. Information on coffee consumption and occupation was re-coded following standard criteria. Unconditional logistic regression was applied adjusting for age, study center, occupation and gender.

RESULTS

Seventy-nine percent of the study population reported having drunk coffee, and 2.4% were heavy drinkers, reporting having drunk on average ten or more cups per day. There was no excess risk in ever coffee drinkers (OR = 1.0, 95% CI 0.8-1.3) compared to never drinkers. The risk did not increase monotonically with dose but a statistically significant excess risk was seen for subjects having drunk ten or more cups per day (OR = 1.8, 95% CI 1.0-3.3). This excess was seen in both men and women. There was no evidence of an association of the risk with duration or type of coffee consumption. The pooled results were not dependent on the findings of any specific study, but they depended on the type of controls with an overall excess risk observed only for studies using hospital controls.

CONCLUSION

Nonsmokers who are heavy coffee drinkers may have a small excess risk of bladder cancer. Although these results cannot be attributed to confounding by smoking, the possibility of bias in control selection cannot be discarded. On the basis of these results, only a very small proportion of cancers of the bladder among nonsmokers could be attributed to coffee drinking.

Occupation and bladder cancer in European women

OBJECTIVES

We examined the importance of occupational exposures for bladder cancer in women.

METHODS

We combined data from 11 case-control studies conducted between 1976 and 1996 in six European countries. The pooled data comprised 700 incident female cases and 2425 population or hospital controls, aged 30-79 years. Lifetime occupational and smoking history were examined using common coding.

RESULTS

Excess risks were found in only a few of the occupations previously identified at high risk for bladder cancer. Statistically significant excess risks were observed for metal workers, particularly blacksmiths, toolmakers and machine tool operators (OR: 2.0, 95% CI: 1.1-3.6), tobacco workers (OR: 3.1, 95% CI: 1.1-9.3), field crop and vegetable farm workers (OR: 1.8, 95% CI: 1.0-3.1), tailors and dress makers (OR: 1.4, 95% CI: 1.0-2.1), saleswomen (OR: 2.6, 95% CI: 1.0-6.9), and mail sorting clerks (OR: 4.4, 95% CI: 1.0-19.5). About 8% (95% CI: 3.1 19.9) of all bladder cancers in women could be attributed to occupation after adjusting for smoking. The attributable risk was higher in women aged less than 65 years (12%), compared to older women (4%).

CONCLUSIONS

The calculation of the attributable risk on the basis of results from this analysis may have caused some overestimation of the proportion of occupational bladder cancer in women. A significant proportion, however, of bladder cancer cases among European women less than 65 years is likely to be attributed to occupation. This link between bladder cancer in women and occupational factors has received little recognition, probably because studies addressing these issues have predominantly been done in men.

Restaurant smoking restrictions and environmental tobacco smoke exposure

OBJECTIVES

This study evaluated the effectiveness of smoking restrictions.

METHODS

We measured particulate concentrations in restaurants with different levels of allowable smoking.

RESULTS

Mean particulate concentrations were 70% higher in establishments without smoking restrictions compared with those with partial smoking restrictions. Concentrations in nonsmoking restaurants were reduced by an additional 20% to 30%. Measurements of cadmium, an environmental tobacco smoke (ETS) marker, implicated ETS as the major source of particulate in restaurants that allowed smoking.

CONCLUSIONS

Partial smoking restrictions substantially reduce, but do not eliminate, ETS exposure in restaurants. Occupants of nonsmoking restaurants avoid ETS exposure but may experience substantial particulate exposures from cooking emissions.