Impacts of changes in PM_2.5 concentrations and their major components on blood pressure during pregnancy

Sulfate, nitrate, ammonium, organic matter, and black carbon account for more than two-thirds of the total mass of PM_2.5 and have stronger cardiovascular toxicity than other components. However, evidence regarding the gestational cardiovascular toxicity of these PM_2.5 components is lacking. A prospective cohort study was conducted among 1913 pregnant women in Guangzhou, Pearl River Delta, China, from 2017 to 2020. Each participant underwent two office blood pressure (BP) measurements: baseline BP was assessed during the first and second trimesters (mean gestational age: 13.77 ± 2.76 weeks) and follow-up BP was measured during the third trimester (mean gestational age: 39.00 ± 1.46 weeks). The level of the five main PM_2.5 components were estimated using a tracking air pollution dataset. Changes in PM_2.5 component concentrations and BP levels were determined by calculating the differences between follow-up and baseline values. We found that changes in PM_2.5 mass and components significantly affected gestational BP variations (β = 1.88-3.42, P < 0.001). Most associations exhibited an inverted U-shaped non-linear relationship, initially increasing steeply before leveling off, without a clear threshold. Systolic blood pressure (SBP) was more sensitive to concentration changes in PM_2.5 components, with nitrate showing a particularly pronounced effect. Our findings suggest that changes in PM_2.5 mass and its specific components levels were associated with maternal BP, especially increased SBP, with nitrate being the major contributor. Stricter emission reduction measures are needed to mitigate urban pollution sources associated with particulate nitrate.