Exposure to polycyclic aromatic hydrocarbons (PAH) and breast cancer incidence: Evaluating the state of the science

Abstract

Background:Exposure to mixtures of PAHs can occur in certain occupations, from tobacco smoke, specific foods, and contaminated air. Some PAHs exhibit estrogenic activity and links between female breast cancer (BC) and specific PAH exposure sources have been reported. We conducted a state of the science review of epidemiological studies assessing PAH exposure and BC.Methods:We searched PubMed for analytical epidemiology studies and BC incidence or mortality. We mapped, evaluated study quality issues, and summarized findings by type of exposure assessment. Three prospective and 10 case-control studies reported effect estimates specific for PAH exposure. PAH exposure was assessed either (1) across multiple exposures using biomarkers like PAH-DNA adducts in breast tissue (N=2) or blood (N=1), PAH-albumin adducts in blood (N=1), and urinary biomarkers (N=2); or from (2) specific sources, including occupations (N=2), air pollution (N=2), and diet (N=3).Results: Adduct studies showed positive associations with BC; adducts assess a combination of recent exposure (months) and susceptibility and may be subjected to reverse causality. Similarly, all occupational exposure and air pollution studies reported positive associations in overall or subset analyses with stronger associations for higher PAH exposure intensity, exposure from a specific occupational source, or during a specific exposure window. Most studies assessed exposure over long time periods although they suffer from imprecise assessments and potential confounding from co-exposure to other carcinogens. Conflicting findings were observed in urinary biomarkers, which assess very recent exposure, and food intake studies, which are prone to measurement error.Discussion:Most studies across this wide variety of exposure scenarios reported elevated risks in overall and/or in subgroup analyses. However, interpretation of the findings is complicated considering accuracy and specificity of exposure assessment methods, relevant exposure windows, and potential confounding. Studies capturing lifetime exposure, integrating multiple sources, and examining source apportionment will elucidate this evidence base.