PM2.5 and its components and hospitalization for hypertensive disorders of pregnancy in Henan Province, China, 2015-2021: A case-crossover study.

Abstract

Introduction: The short-term effects of exposure to fine particulate matter (PM_2.5) and its five components (sulfate, nitrate, ammonium salt, organic matter [OM], and black carbon [BC]) on hospitalizations for hypertensive disorders of pregnancy (HDP) remains unclear.

Methods: This study enrolled mothers with HDP from January 1, 2015, to December 31, 2021, in five cities in Henan Province, China. Daily data on PM_2.5 were obtained from the Tracking Air Pollution in China, an online public dataset. Time-stratified case-crossover models were performed to assess the short-term single-day (lag0-1) and multi-day (lag01-07) lag effects of PM_2.5 on hospitalizations for HDP and further explored the modification effects of maternal age (<35 years and ≥35 years), season (cold and warm seasons), and the "Three-Year Action Plan to Win the Blue Sky Defense War (before and after June 27, 2018) on the short-term effects.

Results: A total of 8,007 mothers with HDP were recruited. An IQR in exposure to PM_2.5, OM, and BC, was associated with 5.7% (RR: 1.057, 95% CI: 1.002-1.112) (lag01), 6.4% (1.064,1.003-1.126) (lag01), and 6.8% (1.068, 1.001-1.135) (lag05) increases in the risk of HDP, respectively (all P<0.05). The effects of exposure to PM_2.5 and its components were stronger in mothers aged ≥35 years, in the cold season, and in the period before the Action Plan was implemented (P_modification<0.05).

Conclusion: Short-term exposure to PM_2.5 and its components was positively associated with hospitalizations for HDP, particularly among mothers aged ≥35 years, during the cold season and before the implementation of the Action Plan.