UC Irvine-led study connects exposure to air pollution and hypertensive disorders in pregnancy

Newswise — In a first-of-its-kind study led by the University of California, Irvine, researchers found that increased risks for a severe form of hypertensive disorders in pregnancy, preeclampsia and eclampsia, were associated with exposures to fine particulate matter known as PM_2.5, and its components including black carbon and organic matter.  

Corresponding author, Jun Wu professor of environmental and occupational health at the UC Irvine Program in Public Health, collaborated with researchers at Kaiser Permanente and other institutions to publish their findings in the Journal PLOS Medicine.   

Wu and team examined nearly 390,000 electronic health records, dated from 2008 to 2017, from Kaiser Permanente Southern California to examine the associations between gestational hypertension (GH) and preeclampsia and eclampsia (PE-E) in pregnancy and exposure to PM_2.5 and its components to identify windows of susceptibility during pregnancy.  

The study found that higher risks for PE-E were associated with exposure to PM_2.5 total mass, organic matter, and black carbon, but not for GH. The risks are less conclusive for the milder variant of hypertensive disorders in pregnancy (HDP), characterized by isolated elevated blood pressure without systemic involvement.  

The main effect of increased PE-E risk was driven by PM_2.5 black carbon (71%) and PM_2.5 organic matter (26%). The most influential time windows of PM_2.5 exposure associated with PE-E were the late first trimester and second trimester. Hispanic and African American mothers and mothers who live in low- to middle-income neighborhoods may be more vulnerable to air pollution-based PE-E risk.  

“As both health and economic burdens increase with severity of hypertensive disorders in pregnancy, more research on the associations between environmental exposure and reproductive health is needed to protect vulnerable communities,” Wu said. “Our study addressed the gap in the literature to examine the effect of air pollution mixture on different expressions of health complications during pregnancy and to understand corresponding pathophysiology.” 

Industries and vehicles pollute the ambient air with PM_2.5 particles, which are so tiny it can be easily inhaled deep into the lungs leading to a range of health problems. Certain groups are particularly vulnerable to the health effects of PM_2.5 pollution, including pregnant women, children, the elderly, and individuals with pre-existing health conditions. Health complications like hypertensive disorders in pregnancy are dangerous for pregnant women because high blood pressure can develop into convulsive seizures during pregnancy or shortly after giving birth, pre-term birth, and in worst cases cause the mother to go into a coma. 

“Although everyone is affected by air pollution, the risk may disproportionately be higher among women of certain socioeconomic backgrounds, such as women living in poverty and the minority populations in our study, subsequently increasing the burden of HDP,” said Yi Sun first author and former postdoctoral researcher at UCI Public Health. “Identifying the main sources of air pollution associated with HDP is also important to initiate actions targeting this highly modifiable risk factor to mitigate those adverse effects on reproductive health and future generations.”