Occupational exposure to combustion by-products and breast cancer risk in postmenopausal women

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OBJECTIVE: To estimate the association between lifetime occupational exposure to select combustion by-products and postmenopausal breast cancer (BC) risk. MATERIALS AND METHODS: Data from a population-based case-control study among postmenopausal women residing in Montréal, Quebec were used. Cases included 661 women aged between 47 and 75 yr, diagnosed with incident malignant BC between 2008 and 2011. Controls comprised 587 women randomly selected from the Quebec Electoral List, frequency-matched to cases by 5-year age groups. Information on risk factors and lifetime occupational histories was collected by interview. Two industrial hygienists used job histories to assign exposure to 293 agents, including 6 combustion by-products (cooking fumes, diesel engine emissions, leaded and unleaded engine emissions, natural gas combustion products, and polycyclic aromatic hydrocarbons [PAHs]). Unconditional logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for BC risk, both for all tumours and by tumour molecular subtypes, in relation to occupational exposure to the 6 selected combustion by-products. RESULTS: No association was observed between occupational exposure to the 6 selected combustion by-products and postmenopausal BC. However, when considering molecular subtypes, women ever occupationally exposed to PAHs had a suggestive higher risk of Luminal B tumours (ORmodel6 = 2.09, 95% CI: 0.87 to 4.60) compared with those never exposed. Additionally, women ever occupationally exposed to cooking fumes compared with those never exposed had a suggestive higher risk of HER2-enriched tumours (ORmodel6 = 2.63, 95% CI: 0.98 to 6.40). CONCLUSION: Occupational exposure to the 6 selected combustion by-products was not associated with postmenopausal BC. Suggestive higher risks of certain molecular subtypes of BC were observed with exposure to PAHs and cooking fumes. Future larger studies should consider the role of occupational exposures in the aetiology of BC across different molecular subtypes.

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