Lung Cancer Mortality and Polynuclear Aromatic Hydrocarbons: A Case-Cohort Study of Aluminum Production Workers in Arvida, Quebec, Canada

Abstract

The authors report the results of a case-cohort study of 338 lung cancer deaths in 1950-1988 and a random sample (sub-cohort) of 1,138 from among 16,297 men who had worked at least one year between 1950 and 1979 in manual jobs at a large aluminum production plant. In the past, certain workers were exposed to substantial quantities of coal tar pitch volatiles, a mixture known to include polynuclear (polycyclic) aromatic hydrocarbons, and thus suspected to be capable of causing lung cancer. After they controlled for the effects of smoking, the authors found that rate ratios rose with cumulative exposure to coal tar pitch volatiles measured as benzene-soluble material to 2.25 (95% confidence interval (CI) 1.50-3.38) at 10-19 mg/m3-years benzene-soluble matter, but did not rise further at higher exposures. The data are compatible with a linear relation with benzene-soluble matter (rate ratio (RR) = 1 + 0.031 mg/m3-years benzene-soluble matter). This model predicts a rate ratio of 1.25, and lifelong excess risk of 2.2%, after 40 years exposure at the current hygiene standard (0.2 mg/m3). A curved relation (RR = 1 + 0.098 mg/m3-years benzene-soluble matter 0.7) fitted somewhat better. Under this model, the predicted risks after this exposure are higher: 1.42 and 3.8%. The data are compatible with both additive and multiplicative models for the combined effect of smoking and coal tar pitch volatiles.

Genotoxic exposures of potroom workers

“…Before that, the exposure levels have probably been considerably higher. In Canadian aluminum smelters, where epidemiologic studies have revealed increased risks for both lung and bladder cancer for the workers, the TWA levels for B[a]P in air have been estimated to have been 10-20 pg/m3 during the relevant time period (2,3). According to a risk assessment model derived from these data, a mean B [alp exposure of 1 pg/ m3 during a 40-year period would result in a slightly less than doubled relative risk for bladder cancer.…”

“…This process has previously caused high airborne exposure levels of coal tar pitch volatiles, containing polycyclic aromatic hydrocarbons (PAH) (1). Potroom workers have increased risks for both bladder and lung cancer (2)(3)(4), probably due to the PAH exposure. Due to technical improvements in the plants, the airborne exposure levels have, however, been reduced during recent years.…”

Cancer Risk Assessment, Indicators, and Guidelines for Polycyclic Aromatic Hydrocarbons in the Ambient Air

“…The exposure to PAHs in an aluminum production plant (Armstrong et al 1994) gave a quantitative risk estimate of 1 × 10 -5 per ng B[a]P/m 3 as workplace exposure for 40 years. If converted to lifetime continuous exposure, the corresponding lifetime unit risk for respiratory cancer would be approximately 9 × 10 -5 per ng/m 3 (70/40 years × 365/220 days × 24/8 hr).…”

“…Based on the similarity of the PAH profiles in urban air and in an aluminum smelter workplace (seven measured PAH compounds; see Special Report • Boström et al below, "United Kingdom"), the panel concluded that occupational studies on workers at aluminum smelters form a suitable basis for recommending an environmental standard. The study chosen was the Canadian study on aluminum workers by Armstrong et al (1994). In this study, a 50% increase in the risk of lung cancer was demonstrated, with a cumulative exposure to B[a]P as indicator substance at levels of 10-100 µg/m 3 × year (equivalent to an exposure to 0.25-2.5 µg/m 3 B[a]P for 40 years).…”

Benzo[b]fluoranthene, a Potential Alternative to Benzo[a]pyrene as an Indicator of Exposure to Airborne PAHs in the Vicinity of Söderberg Aluminum Smelters

“…1,2 Similar findings have been reported among workers in aluminum smelters. [3][4][5][6][7] Two important anthropogenic sources of PAHs are the Söderberg primary aluminum vertical stud smelters (VSSs) and horizontal stud smelters (HSSs). The carbon anodes used in the process contain coal tar pitch, which acts as a binder.…”