Academic journal article Environmental Health Perspectives

Air Pollution, Clustering of Particulate Matter Components, and Breast Cancer in the Sister Study: A U.S.-Wide Cohort

Academic journal article Environmental Health Perspectives

Air Pollution, Clustering of Particulate Matter Components, and Breast Cancer in the Sister Study: A U.S.-Wide Cohort

Article excerpt

Introduction

Air pollution is classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen (Loomis et al. 2013), consistent with the epidemiologic evidence for the role of air pollution in lung cancer incidence (Hamra et al. 2015). However, less is known about the association between air pollution and breast cancer. Air pollution exposure is widespread and thus has the potential to have a substantial impact on the incidence of breast cancer, which is the most common cancer diagnosed among women in the United States (Siegel et al. 2019).

Air pollution contains many carcinogens and other compounds that may act as endocrine disruptors--including polycyclic aromatic hydrocarbons (PAHs), metals, and benzene--which may influence breast cancer risk. Ecologic studies suggest that breast cancer risk is elevated in urban areas with higher air pollution in comparison with rural areas (Chen and Bina 2012; Wei et al. 2012). Some population studies have reported associations between air pollution and breast cancer, as reviewed by White et al. 2018, especially in studies that consider markers of traffic-related pollution such as nitrogen dioxide (N[O.sub.2]), nitrogen oxides (N[O.sub.x]), and PAH exposure (Bonner et al. 2005; Hystad et al. 2015; Mordukhovich et al. 2016; Nie et al. 2007; Reding et al. 2015). In the Sister Study cohort, Reding et al. (2015) reported a modest association between residential N[O.sub.2] levels and risk of estrogen and progesterone receptor-positive ([ER.sup.+] [PR.sup.+]) breast cancer. However, associations with measures of particulate matter (PM) <2.5 [micro]m and <10 [micro]m in aerodynamic diameter ([PM.sub.2.5] and [PM.sub.10], respectively) have not been consistently observed (Andersen et al. 2017a, 2017b; Hart et al. 2016; Reding et al. 2015; Villeneuve et al. 2018).

Fine particulate matter ([PM.sub.2.5]) is a complex mixture that varies in composition geographically due to varying sources, differences in meteorology, and other factors (Bell et al. 2007). Regional differences in particulate matter have been shown to modify the association with breast density, an important predictor of breast cancer risk (DuPre et al. 2017). Associations between [PM.sub.2.5] and health effects such as blood pressure (Keller et al. 2017), cardiovascular disease (Brook et al. 2010), and mortality (Franklin et al. 2008) have been shown to vary significantly by [PM.sub.2.5] component profiles. In this report, we have extended our prior research on the relationship between air pollutants and breast cancer risk (Reding et al. 2015) with additional years of follow-up and case accrual and expanded this work to include consideration of effect measure modification by [PM.sub.2.5] components and breast cancer risk using predictive k-means clusters (Keller et al. 2017). We hypothesized that air pollution would be related to breast cancer risk and that associations for [PM.sub.2.5] would vary by [PM.sub.2.5] component cluster. Breast cancer is a heterogenous disease (Polyak 2011). Associations with established breast cancer risk factors have been shown to vary by hormone receptor status [often defined by the presence or absence of the estrogen receptor (ER) and progesterone receptor (PR)] (Anderson et al. 2014) as well as by menopausal status at diagnosis (White et al. 2015). In addition, risk factors may vary by whether the tumor is invasive or ductal carcinoma in situ (DCIS) (Barclay et al. 1997). Previous research on the association between air pollution and breast cancer has been inconclusive on whether associations vary by these different outcome classifications; therefore, we also evaluated the risk associated with air pollutant exposure considering these different outcome definitions.

Methods

Study Population

The Sister Study is a nationwide prospective cohort designed to investigate environmental and lifestyle risk factors for breast cancer (Sandler et al. …

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