Wildfire smoke caused unhealthy levels of air pollution across Washington, D.C., in mid-July as fires raged across Ontario, Canada. A new study examining years between 2003 and 2019 found that the primary pollutant affecting pregnancies was wildfire smoke. (Photo by Finn Gomez/Getty Images) A new study examining pollution levels across a 16-year span found that while general pollution levels from sources such as cars and industry have significantly declined, recent increases in wildfire smoke air pollution have offset those gains and could be contributing to negative outcomes for pregnant women and babies such as low birth weight and preterm births. Published by Frontiers in Environmental Health, the study included data from about 64.5 million pregnancies between 2003 and 2019, covering more than 2,800 counties in 48 states. Even in regions that are not strongly associated with wildfire, such as the southeast region of the U.S., wildfire pollution rates grew substantially during ...