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p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px 'Helvetica Neue'} Background: Emerging evidence suggests that environmental endocrine disrupting chemicals, such as polycyclic aromatic hydrocarbons (PAHs), increase breast cancer risk. Polycyclic organic matter (PAHPOM) is a USEPA Environmental Quality Index (EQI) air domain factor, which includes PAHs and PAH-derivatives present in the atmosphere in particulate form. Sources include tobacco smoke, vehicle exhaust, residential heating, coal and tar burning, and grilling meat. Methods: Herein, we investigated associations between polycyclic organic matter exposure and invasive breast cancer. Breast cancer diagnoses were obtained from the North Carolina Central Cancer Registry (2009-2014), and county of residence at diagnosis was linked with the quartiled PAHPOM variable. We first constructed generalized linear models to assess county-level breast cancer incidence by stage in counties of high versus low PAHPOM exposure, adjusted for mammography screening rates, %African American, and %Smokers. Next, we constructed generalized estimating equations to evaluate the odds of individual patients having localized, regional, or distant invasive breast cancer versus non-invasive carcinoma in situ in counties of high versus low PAHPOM exposure, adjusted for age, BMI, smoking status, and race. We further evaluated the odds of patients having hormone receptor positive versus hormone receptor negative invasive breast cancer. All models were stratified by urbanicity. Results: High PAHPOM exposure was associated with increased total and localized breast cancer incidence (total estimate 22.36, 95% CI 6.77-37.95, p=0.006; localized estimate 12.43, 95% CI 3.36-21.5, p=0.008), as well as increased odds of having hormone receptor positive versus hormone receptor negative invasive breast cancer (OR 1.04; 95% CI: 1.00, 1.08, p=0.0187) in urban counties. Conclusions: Our results suggest that high polycyclic aromatic compound exposure is associated not only with increased breast cancer incidence, but also increased odds of having hormone receptor positive invasive breast cancer, especially in urban areas.