Adequacy of Benzo(A)Pyrene and Benzene Soluble Materials as Indicators of Exposure to Polycyclic Aromatic Hydrocarbons in a Söderberg Aluminum Smelter

Abstract

Occupational and environmental exposure to polycyclic aromatic hydrocarbons (PAHs) occurs as a complex mixture that is evaluated using specific components, such as benzo(a)pyrene (BaP) and benzene soluble materials (BSM). Factors that influence the relationship between BaP, BSM, and other PAHs within an aluminum smelter were investigated. Personal samples collected from 1978 to 2001 were used: 576 samples were analyzed for both BaP and BSM; 479 samples were analyzed for BaP and nine other particulate PAHs. Differences in the log-transformed ratios (PAH/BaP, BaP/BSM) due to anode paste composition, pot group, season, and job were examined using linear regression. Pot groups represented differences in technology, process conditions, and building properties. The models' predicted PAH/BaP ratios were multiplied by BaP relative potency factors to estimate the relative toxicity of the mixture. The correlation between BaP and BSM depended on the anode paste source (range 0.1–0.8). In linear regression, 27% of the variability in the log-transformed BaP/BSM ratio was explained by coal tar pitch, work area, and job; no seasonal or pot group differences were observed. Within the potrooms, BaP was very strongly correlated with other PAHs (majority > 0.9). Depending on the PAH, between 23% and 89% of the variability in the log-transformed PAH/BSM was explained by season, coal tar pitch, pot group, and job. The BaP toxic equivalency factors of the mixture varied more across job (2.1–3.5) than across coal tar pitch source (1.8–2.8) or pot group (2.3–2.5). Seasonal and work area differences in the relationship between BaP and other PAHs have not been reported previously. Until these relationships are better understood, BaP seems to be a reasonable, albeit imperfect, indicator due to the strong correlation between BaP and other PAHs for a given set of conditions and due to the relative abundance of BaP exposure measurements.

Keywords:

• aluminum smelter
• exposure misclassification
• occupational exposure
• polycyclic aromatic hydrocarbons

ACKNOWLEDGMENTS

The authors thank the joint ALCAN/Canadian Auto Workers advisory committee for their assistance. The authors also thank Barry Boudreault, Jim Thorne, Nela Walter, and Mary Lo for their assistance in abstracting historical information. This research was partially supported by grants from Alcan and the Workers' Compensation Board of BC. Trainee support for MF was provided by the Michael Smith Foundation for Health Research and the Canadian Institutes for Health Research.

Notes

^A p < 0.10 in Mann-Whitney two sample comparison compared with Potroom Operations “Far” jobs and Kosco/VFT (50/50) coal tar pitch mixture.

^A Pitch type not significant (p > 0.10).

^B No measurements to assess effect.

^A Source: Willes et al., Reference 13.

^B Sum of BEF × BaP RAR for selected PAHs.