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."