Hazardous air pollutants and breast cancer risk in California teachers: a cohort study

Abstract

BackgroundStudies suggest that higher breast cancer rates in urban areas persist after accounting for the prevalence of known risk factors, leading to speculation that urban environmental exposures, such as air pollution, may play a role in the etiology of breast cancer. Combining modeled ambient air concentrations with data from a large prospective cohort of California women with over 15 years of follow-up, we examined the relationship between breast cancer incidence and modeled concentrations of air pollutants shown to be mammary gland carcinogens (MGCs).MethodsThe study population of 112,378 California Teachers Study participants included 5,676 women diagnosed with invasive breast cancer. Modeled annual average ambient air concentrations of 24 MGCs from the U.S. Environmental Protection Agency were linked to participants’ addresses. Cox proportional hazards models were used to estimate hazard rate ratios and 95% confidence intervals associated with residential MGC levels. MGCs were examined individually and as a combined summary variable for all participants, in selected subsets, and by tumor hormone responsiveness.ResultsInitial models yielded some evidence for increased risk for several compounds, including acrylamide, carbon tetrachloride, chloroprene, 4,4'-methylene bis(2-chloroaniline), propylene oxide, and vinyl chloride, but after adjustment for multiple comparisons, only results for propylene oxide and vinyl chloride remained statistically significant. In subset analyses, estrogen-receptor positive or progesterone-receptor positive (ER+/PR+) tumors were associated with higher ambient levels of acrylamide, benzidine, carbon tetrachloride, ethylidene dichloride, and vinyl chloride, while ER-/PR- tumors were associated with higher ambient levels of benzene. Interesting results for different compounds were observed within certain subsets of the population.ConclusionWhile our initial models yielded several elevated risk estimates, after adjusting for multiple comparisons and breast cancer risk factors, most hazard ratios were no longer statistically significant. Our subset analyses, however, suggest that elevated risk may be associated with some compounds for certain subgroups of interest. A summary variable for all 24 MGCs did not offer any advantage over the models for individual compounds. Results must be interpreted cautiously, as estimated exposure was limited to modeled annual average ambient air concentrations, and could not account for other sources or routes other than inhalation.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-069X-14-14) contains supplementary material, which is available to authorized users.

Serum Levels of Selenium and Zinc in Patients with Breast Cancer: A Case-Control Study

“…Human and laboratory studies have been conducted on the role of these 2 elements in preventing carcinogenesis process and tumor cell growth (19)(20)(21)(22). On the other hand, epidemiological studies have shown that differences in dietary habits or diet (23,24) and air pollution (25) can effect on risk of BC, in line with genetics (26). In Ku's study, it was suggested that change the vital elements in serum and tissue might be beneficial and considerable biomarkers in BC (27).…”

Exposure to multiple sources of polycyclic aromatic hydrocarbons and breast cancer incidence

“…Research on the health effects of the air pollutant benzene has historically focused on occupationally-exposed men (IOM (Institute of Medicine) 2012). However, a study in New York did find an association among women who were likely to have moderate to high exposure based on job-exposure matrices (Petralia et al 1999) and an association was observed with ER-PR- tumors in the California Teacher’s Cohort study (Garcia et al 2015). …”

Environmental Determinants of Breast Cancer

“…The study found suggestive associations for NO 2 , and the US Sister Study found significantly higher risk of ER+/PR+ tumors with NO 2 exposure (112). The California Teachers Study found associations between ER+/PR+ tumors and some mammary gland carcinogens (44) and between ER−/PR− tumors and ambient benzene (44), cadmium, and arsenic (77). The Nurses' Health Study II did not find these associations (48), but the cohort was younger than that of the California Teachers Study.…”