Independent and combined effects of PM2.5 and its constituents on preterm birth: a retrospective study in a seaside city.

Mounting studies explored associations between fine particulate matter (PM_2.5) and preterm birth (PTB); however, individual and combined impacts of PM_2.5 constituents on PTB were less known. PM_2.5 and its seven constituents were assessed by V4.CH.02 product of the Dalhousie University Atmospheric Composition Analysis Group, a dataset containing combined geophysical-statistical estimates of PM_2.5 across China. Effects of PM_2.5 and its constituents on PTB and gestational age were firstly explored. Furthermore, weighted quantile sum (WQS) regression was conducted to reveal the impacts of total PM_2.5 mass and identify contributing constituents. An interquartile range (IQR) increase in PM_2.5 was associated with increased odds ratio (OR) of PTB. PM_2.5 constituents were widely associated with PTB and reduced gestational age, with different time window. The total mass of PM_2.5 (per IQR increment) in the first and the second trimester was positively associated with PTB by WQS regression (Trimester 1: OR = 1.38, 95%CI: 1.15, 1.65; Trimester 2: OR = 1.47, 95%CI: 1.21, 1.79). The most contributing factors were black carbon in the first trimester and sulphate ion in the second trimester, respectively. Especially, sea salt was identified as contributing constituent during the first trimester. The study indicated that prenatal exposure to PM_2.5 and its constituents was individually and jointly associated with PTB and reduced gestational age. Sea salt was firstly identified as a risk factor of PTB in the seaside city, which needs further exploration. [ABSTRACT FROM AUTHOR]