The leading hypothesis about how the particulates do harm relates to their ability to burrow deep into the lungs, says Edelman, spurring the release of inflammatory cytokines. Chronically, this can lead to low-level systemic inflammation, an underlying factor in many common diseases from diabetes to cardiovascular disease and cancer. Pollutants also appear to trigger changes in the part of the nervous system that regulates blood pressure and blood vessel constriction. Some evidence suggests that the smallest particulates might even pass into the bloodstream—just like oxygen—and damage other organs directly.
While there is little an individual can do to affect air quality in the short term, grander measures would carry a public health benefit, experts say. "Reduction in ozone [and other pollutants] will likely lead to improvements in rates of lung and heart disease," says Robert Brook, a University of Michigan cardiologist who researches the health effects of air pollution.
Even seemingly small local measures can be meaningful, says Edelman—pushing for a no-idling policy on school yard premises, say. "School bus drivers often don't like to turn off their engines" when waiting for students in the school yard, he says. Kids often run around blowing off steam after the school day—which draws air, and pollutants, deeper into their lungs. And school buses' "diesel engines spew huge amounts of particulate matter," he adds.