Ozone also reacts with a slew of plastics and other reactive surface molecules, ranging from carpet fibers to the skin's natural oil, to produce toxic chemicals like formaldehyde and other irritants. "Reaction chemistry suggests that the stuff being created is worse than ozone itself," Apte says. "It's like atmospheric chemistry but it's going on in building atmospheres rather than out in the sunlight." In other words, ozone seeping into buildings combines with other chemicals to produce more noxious air.
Researchers estimate that exposure to unhealthy ozone is cumulatively greater from such indoor air pollution than from concentrations that are as much as 10 times higher outside, because people spend the majority of their day indoors. As a result, sick building syndrome costs the U.S. economy as much as $60 billion annually in lost productivity. Installing filters designed to catch ozone before it gets into office air—as well as cutting back on the ozone-forming tailpipe pollution of all those commuters—would help, Apte says. And the problem could be reduced by 75 percent, the study finds, simply by switching from polyester to fiberglass filters in the smoggiest areas.
After all, the ventilation system turned out to be the culprit in the first sick building affliction: Legionnaire's disease, named for a mysterious pneumonia outbreak at an American Legion convention in 1976. The illness was found to come from Legionella bacteria thriving in the hotel's cooling tower and spread through its air conditioning system.
Outdoor ozone air pollution interacting with indoor filters and environments may prove a root cause of at least some of the otherwise unexplained sick building symptoms, Apte says. "I'm hoping that this ozone finding continues to provide an explanation of at least some of the variance in the distribution of symptoms people experience in buildings, though I don't believe this can explain all of them," he notes. "Some day it will no longer be called sick building syndrome."