Exposure-Lag-Response Association between Prenatal Ambient Air Pollution Exposure and Preterm Birth in Guangzhou, China

Abstract

Prenatal trimester-specific air pollution exposure has been associated with preterm birth (PTB), however, little is known about the effects of gestational week specific exposure on PTB and critical exposure windows are still unclear. Using data from the Guangzhou Birth Registry including 506,210 singleton live births between January 2015 and July 2017, we assessed the susceptible exposure windows during pregnancy at weekly level. Daily average concentrations of PM2.5, PM10, NO2, SO2, and O3 from 11 monitoring stations were used to estimate district-specific exposures for each participant based on residential addresses during pregnancy. Distributed lag models (DLMs) were applied to estimate the association between weekly-specific maternal air pollutant exposures and PTB, after controlling for temperature, seasonality, and individual covariates. Hazards ratios (HRs) and 95% confidential intervals (95%CIs) were calculated for an interquartile range (IQR) increase in air pollutants during the study period. Multi-pollutant models were also performed. PTB risk was significantly associated with PM2.5 exposure during the17th to 25th gestational week, with the strongest effect in the 22nd gestational week (IQR=27.0 ug/m3; HR=1.04, 95%CI:1.02-1.06). The significant exposure windows were 14th-30th gestational weeks for PM10, 9th-27th for NO2, and 19th-28th for O3, respectively. Corresponding peak associations were observed in the 25th gestational week for PM10 (IQR=37.0 ug/m3; HR=1.04, 95%CI:1.02-1.05), in the22nd for NO2 (IQR=29.0 ug/m3; HR=1.03, 95%CI:1.02-1.05), and in the 24th for O3 (IQR=90.0 ug/m3; HR=1.06, 95%CI:1.04-1.08). No significant association between pregnancy SO2 exposure and PTB was observed. In multi-pollutant models, effects of each pollutant retained but were slightly reduced. Our results suggest critical air pollution exposure windows for PTB risk vary slightly among air pollutants, while the mid-gestation was similarly observed as a susceptible period.