Adult air pollution exposure and risk of infertility in the nurses' health study II
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BACKGROUND: Exposures to air pollution has been associated with lower conception and fertility rates. However, the impact of pollution on infertility is unknown. OBJECTIVES: To examine the associations of roadway proximity (a measure of traffic exposure) and particulate matter (PM) air pollution and incidence of infertility. METHODS: Proximity to major roadways and ambient exposures to particulate matter less than 10 microns (PM10), between 2.5 and 10 microns (PM2.5-10), and less than 2.5 microns (PM2.5) were determined for all residential addresses for 36,294 members of the prospective Nurses' Health Study II cohort from 1993 to 2003. Infertility was defined by report of attempted conception for ≥12 months without success. Participants were able to report if evaluation was sought and if so, offer multiple clinical indications for infertility. Multivariable adjusted Cox proportional hazard models were used to estimate the relation between each exposure and infertility risk. RESULTS: Over 213,416 person-years, there were 2,508 incident reports of infertility. Results for overall infertility were inconsistent across exposure types. We observed a small increased risk in those living closer to compared to farther from a major road, multivariable adjusted hazard ratio (HR)=1.11(95% confidence interval (CI) = 1.02-1.20). Among those reporting primary infertility, risk was greater with closer distance to road and for all PM size fractions and exposure time windows. The multivariable adjusted HR (95%CI) for women living closer to compared to farther from a major road for primary infertility was 1.37 (1.22-1.52), while for secondary infertility HR=1.07 (0.95-1.21). In addition, the HR for every 10 mcg increase in cumulative PM2.5 among women with primary infertility was 1.61 (1.35-1.92), while it was 1.1 (0.91-1.33) for those with secondary infertility. CONCLUSIONS: This study suggests exposures to traffic and PM may be associated with a small increased risk of infertility, especially primary infertility.