Exposure to low concentrations of PM and its constituents with preterm birth in Shenzhen, China: a retrospective cohort study.

BACKGROUND

Due to the Air Pollution Prevention and Control Measures issued by the Chinese government, air quality has significantly improved, particularly with respect to PM. However, studies on the relationship between low concentrations of PM and preterm birth (PTB) remain limited in China.

OBJECTIVE

To examine the associations between low concentrations of PM and its constituents and PTB.

METHODS

This retrospective cohort study was conducted from July 2021 to April 2023 in Shenzhen, China. Data on questionnaires and pregnancy outcomes were collected for each participant. Using the Tracking Air Pollution in China (TAP) dataset, we assessed the concentrations of PM and its chemical constituents, including sulfate (SO), nitrate (NO), organic matter (OM), black carbon (BC), and ammonium (NH). We applied a generalized additive model (GAM) to evaluate the relationship. The relationship between exposure to PM and its constituents and PTB was further examined using a method that combined dummy variable settings with trend tests. Stratified analysis was conducted to explore the potential factors.

RESULTS

Among 17,240 live-born infants, the rate of PTB was 6.0%, and the average exposure concentration of PM was 20.24 μg/m. There were positive associations between PM and its constituents and PTB. With each interquartile range (IQR) increase in PM during the third trimester, the risk of PTB increased by 2.23 times. The exposure effects of sulfate (SO) and organic matter (OM) were comparable to the total PM. The third trimester might be the critical susceptibility window. The risk was higher among women who conceived in the cold season and were exposed to higher temperatures during pregnancy.

CONCLUSION

Even at low levels, PM can still increase the risk of PTB, with varying health effects attributed to different constituents. This underscores the importance of further strengthening environmental management and characterizing the contributions of PM sources.