E&E News | Sean Reilly Small children were much more likely to develop asthma if their mothers were exposed during pregnancy to high levels of exceptionally tiny specks of pollution, researchers found in a newly released study. The study, published online today in the American Journal of Respiratory and Critical Care Medicine, followed about 375 mostly Black and Latino women in the Boston metro area during pregnancy and after they gave birth in tandem with their estimated exposure to ultrafine particle pollution. Overall, researchers found that more than 18% of children born to those women developed asthma as preschoolers, or more than double the 7% rate for the United States as a whole, according to the paper and an accompanying summary. The summary also noted many of the subjects were more likely to live near busy roads, where exposure to ultrafine particles tended to be higher. “This research is an important early step in building the evidence base that can lead to better monitoring of exposure to ultrafine particles in the United States and ultimately to regulation,” Dr. Rosalind Wright, the lead author and a professor at the Mount Sinai Health System’s Icahn School of Medicine in New York City, said in an accompanying statement. Ultrafine particulate matter, produced by vehicle tailpipe exhaust and other sources, is no bigger than 0.1 micron in diameter, or approximately one-thousandth the width of a human hair. Those particles are not explicitly regulated or monitored by EPA, whose ambient air quality standards set a cutoff of 2.5 microns in diameter. What’s technically known as PM2.5 is already associated with worsened asthma symptoms in children and other respiratory effects.