As many as 7,000 babies were born prematurely because of exposure to wildfire smoke between 2007 and 2012, new research from Stanford discovered. The study, published in Environmental Research, found the more days a pregnant person was exposed to smoke the more likely they were to have a preterm birth. A Week of exposure increased risk of preterm births by 5% and a month caused a 20% increase. “The smoke exposure then was dramatically less back then,” study co-author Marshall Burke told the Guardian. “Four of the last five years have seen worse smoke than any year in our sample.”

Just this week, smoke from the Caldor Fire has made air quality in the Lake Tahoe region worse than some of the most polluted cities in the world. Some Nevada counties also experienced their worst air quality on record. The main culprit is fine particulate matter in the smoke (technically known as PM2.5). PM2.5 infiltrates the lungs and causes or worsens a wide range of severe health impacts, including COVID-19. Racist policies and practices disproportionately burden people of color with PM2.5 pollution, which is also produced by burning fossil fuels, which causes climate change and supercharges the wildfires. The study is consistent with others finding harm to children exposed to PM2.5 pollution, and wildfire smoke in particular, in utero. (The Guardian, New York Times $; NV air quality: The Hill; Climate Signals background: Wildfires)