Prenatal exposure to ozone and bone mineral density in early childhood: Susceptible window identification.

Abstract

Background: The effect of prenatal ozone exposure on early childhood bone mineral density (BMD) remains to be explored.

Methods: This study was based on the pediatric subcohort of the Fujian Birth Cohort Study. The mean ozone exposure concentration was calculated for the entire pregnancy, as well as for each trimester (first, second, and third) and for every gestational week. BMD was assessed using quantitative ultrasonography (QUS). Low BMD was defined as a z-score of less than -1. Linear and logistic regression models were used to assess the effect of maternal ozone exposure. Distributed lag models (DLMs) were applied to identify the sensitive windows of ozone exposure.

Results: 1345 mother-offspring pairs were included in this study. We found that for every interquartile range (IQR) increase in ozone levels of different exposure durations (entire pregnancy, first, second, and third trimester), BMD z-scores decreased by 0.12 (95 % CI: 0.18, -0.07), 0.07 (95 % CI: 0.11, -0.02), 0.08 (95 % CI: 0.14, -0.02), and 0.07 (95 % CI: 0.13, -0.01), respectively. For low BMD, an IQR increase in ozone levels was associated with 1.47 times higher odds of low BMD (95 % CI: 1.09, 1.98) in the second trimester. The most pronounced negative association with BMD z-scores was observed between the 9th and 16th gestational weeks. For low BMD, the highest OR was observed between the 15th and 17th gestational weeks.

Conclusions: Prenatal exposure to ozone was inversely associated with BMD in early childhood, with early to mid-pregnancy identified as the susceptible window.