Associations between wildland fire smoke PM_2.5 and maternal blood pressure

Wildland fires are a significant source of pollution that can cause sudden changes in ground-level ambient fine particulate matter (PM_2.5), an exposure that has been associated with gestational blood pressure increases. However, estimating the health risks specific to wildland fire smoke PM_2.5 is often encumbered by limitations to smoke plume modeling.

We utilized a novel approach to estimate and characterize wildland fire smoke PM_2.5 in Reno, Nevada, USA, an area prone to seasonal smoke from wildland fires. Daily, 24-h averaged, plume-specific wildland fire smoke PM_2.5 concentrations were estimated at two air quality monitoring stations, and each plume was categorized by both the intensity of the source fire (high vs. low intensity) and the primary fuel type (forest, shrub/scrub, grassland, and other). Using electronic medical records (2012-2019), we identified a set of healthcare encounters of pregnant individuals, assigned these encounters to the air quality monitor closest to the maternal residential address at the time of the encounter and estimated the acute effects (0 to 3 day lag periods) of wildland fire smoke PM_2.5 on maternal systolic and diastolic blood pressure measures across gestational periods using a multi-level linear regression model.

We evaluated 132,570 clinical encounters with a blood pressure measurement over 22,399 pregnancies (median 4.0 measures per pregnancy). Overall, we found null associations between wildland fire smoke PM_2.5 and maternal blood pressure, regardless of the lag period. However, there was evidence that suggested associations could differ between gestational exposure periods, as positive associations not meeting statistical significance criteria were observed for almost all first trimester exposures. Associations did not differ by fire intensity or fuel type.

We did not find evidence for short-term associations between wildland fire smoke PM_2.5 and maternal blood pressure. Similar to other studies in the field, challenges to modeling smoke plumes and subjects altering their behavior during smoke events may be impacting the analyses.