This week, weather forecasters in Washington, D.C., issued their first ozone alerts of the year. Announcing the arrival of "code orange" weather, an unhealthy confluence of heat and pollution, they advised people with respiratory problems to stay indoors and avoid exercise.
However, even robust individuals may suffer temporary, subtle damage—leaky lungs—by breathing ozone concentrations below those needed to trigger such alerts, according to a European study reported this week in Toronto at the American Thoracic Society meeting.
The study indicates that even in regions meeting the U.S. air-quality standard for ozone, "there's a potential risk to human health," contends study leader Alfred Bernard of the Catholic University of Louvain in Brussels, Belgium. As such, he told Science News, the current U.S. ozone limits appear to offer "no margin of safety."