Cities like Houston are dotted with air-sniffing monitors that measure levels of benzene and other potentially unhealthy air pollutants. But those monitors can't answer the question we care about most: Is the air safe?
That's because there's no simple relationship between toxic air pollutants and health risks. Researchers at the University of North Carolina in Chapel Hill are trying to get a leg up on that problem. They are building an instrument that uses human lung cells to measure health hazards in the air more directly.
If you stand in front of Almena and Sidney Poray's house in Baton Rouge, La., and look straight down the street, past the other houses and the shade trees, you see more than a dozen plumes of exhaust in various hues of gray and white.
"That's something you see every day, the same thing if not more," says Almena Poray. "Sometimes it's a darker gray; sometimes it's a black smoke coming out."
Denise Mauzerall arrived in Beijing this year at a time that was both horrifying and illuminating. The capital was facing some of its worst pollution in recent memory, and Mauzerall, a Princeton environmental engineering professor, was passing through on her way to a university forum on the future of cities.
"I took the fast train from Beijing to Shanghai, and looking out the window for large sections of that trip, you couldn't see more than 20 feet," Mauzerall recalled.
To Mauzerall, the lesson was surprising and inescapable.
If you're driving down the road someday and you come across a camper with a 50-foot periscope sticking up into the sky, you just might have crossed paths with Ira Leifer. His quirky vehicle is on a serious mission. It's sniffing the air for methane, a gas that contributes to global warming.
Leifer is an atmospheric scientist at the University of California, Santa Barbara. But you'll more often find him off campus, in a garage, next to a string of auto body shops near the airport.