Maternal Exposure to Surface Ozone and Reduced Fecundity in China: Evidence from a Nationwide Survey.

The influence of ground-level O, which possesses a higher oxidative concentration than other ambient pollutants, on reproductive health has received relatively limited scrutiny. In this study, we collected information on reproductive history, sociodemographic profiles, lifestyle, and residential details of 10,153 couples at risk of pregnancy. Each participant's 1-year, 3-year, and 5-year average O exposure levels were estimated using a previously developed randomized trees model. We used discrete-time Cox proportional hazards models to estimate the fecundability odds ratio (FOR) for each 10 μg/m change in the O, adjusting for a set of demographics, lifestyle, and environmental covariables. We observed that a 10 μg/m increase in the annual average level of exposure to O was associated with a 16% reduction in fecundity (FOR: 0.84; 95% CI: 0.82-0.85). We also observed a 40% increase in the odds of infertility (OR: 1.40; 95% CI: 1.34-1.46) for each 10 μg/m rise in the annual mean of O exposure. After adjustment for fine particulate matter, the strong association between O exposure of fecundity to O persisted. Given the increasing epidemic of infertility, we strongly advocate for heightened consideration of O's impact on reproductive health, as it may partially counterbalance the health benefits gained from improved PM levels in a middle-income setting.