Even healthy young adults may suffer ill effects from air pollution.

For three consecutive winters, researchers traced levels of air pollution at three monitoring sites in and near Provo, Utah, where air pollution varies predictably with the weather and snow cover. They took blood samples from 72 healthy young volunteers, average age 23, all of them nonsmokers unexposed to secondhand smoke at home, work or school.

The study, in Circulation Research, found consistent relationships between levels of air pollution and damage to cells in the endothelium, the inner lining of the blood vessels. Increasing pollution also suppressed factors that led to growth of blood vessels. And as pollution levels rose, so did blood levels of cytokines, chemical messengers that are another indicator of inflammation. All of these factors contribute to cardiovascular disease.

“This provides very important mechanistic evidence regarding how air pollution affects cardiovascular disease,” said the lead author, C. Arden Pope III, a professor of economics at Brigham Young University. “These are healthy nonsmokers, and yet you see this subclinical injury even in these very young people. The initial vascular injury is likely to be minor, but prolonged exposure can contribute to the risk of life-threatening events like stroke and heart attack.”