摘要：Background: Particulate matter (PM) is a complex mixture. Geographic variations in PM may explain the lack of consistent associations with breast cancer. Objective: We aimed to evaluate the relationship between air pollution, PM components, and breast cancer risk in a United States-wide prospective cohort. Methods: We estimated annual average ambient residential levels of particulate matter < 2.5 μ m and < 10 μ m in aerodynamic diameter ( PM 2.5 and PM 10 , respectively) and nitrogen dioxide ( NO 2 ) using land-use regression for 47,433 Sister Study participants (breast cancer–free women with a sister with breast cancer) living in the contiguous United States. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk associated with an interquartile range (IQR) increase in pollutants. Predictive k -means were used to assign participants to clusters derived from PM 2.5 component profiles to evaluate the impact of heterogeneity in the PM 2.5 mixture. For PM 2.5 , we investigated effect measure modification by component cluster membership and by geographic region without regard to air pollution mixture. Results: During follow-up ( mean = 8.4 y ), 2,225 invasive and 623 ductal carcinoma in situ (DCIS) cases were identified. PM 2.5 and NO 2 were associated with breast cancer overall [ HR = 1.05 (95% CI:0.99, 1.11) and 1.06 (95% CI:1.02, 1.11), respectively] and with DCIS but not with invasive cancer. Invasive breast cancer was associated with PM 2.5 only in the Western United States [ HR = 1.14 (95% CI:1.02, 1.27)] and NO 2 only in the Southern United States [ HR = 1.16 (95% CI:1.01, 1.33)]. PM 2.5 was associated with a higher risk of invasive breast cancer among two of seven identified composition-based clusters. A higher risk was observed [ HR = 1.25 (95% CI: 0.97, 1.60)] in a California-based cluster characterized by low S and high Na and nitrate ( NO 3 − ) fractions and for another Western United States cluster [ HR = 1.60 (95% CI: 0.90, 2.85)], characterized by high fractions of Si, Ca, K, and Al. Conclusion: Air pollution measures were related to both invasive breast cancer and DCIS within certain geographic regions and PM component clusters.
