Summer Ozone Tied to Risks for Unborn Children

Ozone pollution during pregnancy significantly increases the risk of intellectual disability in children, according to a new U study. The research, published in the Journal of Exposure Science & Environmental Epidemiology, found that exposure during the second trimester—when fetal brains produce 250,000 neurons per minute—was most critical.

Ground-level ozone, a highly reactive oxygen molecule, is a growing summertime pollution hazard in Utah, particularly as the climate warms. It forms when emissions from vehicles, industry, and other sources interact with sunlight, creating harmful air quality conditions. Long linked to respiratory issues, ozone is now also being examined for its impact on brain development. The federal standard for ozone is 70 parts per billion, a limit often exceeded on the Wasatch Front during summer.

“The body of evidence suggests that it is important that we never take our foot off the gas in terms of working to reduce the levels of air pollution that Utahns are breathing,” says sociology professor Sara Grineski, who led the research.

The findings are especially relevant for Utah, where summer ozone levels frequently spike. A 10-parts-per-billion increase in average second-trimester exposure was linked to a 55.3 percent higher chance of intellectual disability compared to siblings and a 22.8 percent increase compared to population controls.

The research team, which included experts from sociology, psychiatry, and environmental science, analyzed birth data from 2003-14 using the U’s Utah Population Database. They tracked where mothers lived and linked ozone exposure to each trimester, offering new insight into the risks posed by air pollution.