Increment of ambient exposure to fine particles and the reduced human fertility rate in China, 2000-2010.

Epidemiological and toxicological studies suggest that exposure to ambient fine particles (PM) can reduce human reproductive capacity. We previously reported, based on spatial epidemiology, that higher levels of PM exposure were associated with a lower fertility rate (FR) in China. However, that study was limited by a lack of temporal variation. Using first-difference regression, we linked temporal changes in FR and PM with adjustment for ecological covariates across 2806 counties in China during 2000-2010. Next, we performed a sensitivity analysis of the variation in the PM-FR association according to (1) geographic region, (2) indicators of the level of development, and (3) PM concentrations. Also, we quantified the reduction in the FR attributable to ambient PM in China for the first time. The FR decreased by 3.3% (1.2%, 5.3%) for each 10 μg/m increment in PM. The association varied significantly among the geographic regions, but not with the level of development. Nonlinearity analysis suggested a linear exposure-response function with an effect threshold of ~8 μg/m. We also found that comparing to the 2000 scenario, increment of PM in 2010 might result in a reduction of 2.50 (2.44, 2.60) infants per 1000 women aged 15-44 years per year in China. Our results confirm the statistical association between ambient particles and FR and suggest that poor air quality may contribute to childlessness in China.