Wildfire smoke had become the dominant source of the worst air pollution days experienced during American pregnancies by the end of the last decade, according to a national analysis published in Frontiers in Environmental Health. By 2019, roughly 65% of days when prenatal fine particle exposure crossed into unhealthy territory were attributable to wildfire smoke.
The finding rests on an unusually large dataset. Researchers examined about 64.5 million pregnancies between 2003 and 2019 across 2,842 counties in 48 states, linking county-level pollution estimates to demographic data including maternal ethnicity, urban or rural residence, and county income level.
