Ozone in Smog Linked to Cancer in Tests

Researchers said Thursday that animal experiments suggest the ozone in air pollution, already recognized as a cause of headaches and breathing difficulties, may also trigger cancer.

Scientists at Columbia and Rutgers universities found that high doses of ozone, which makes up a large proportion of the smog over many cities, can cause a transformation in animal cells similar to cancer.

“Humans are exposed all over the place” to ozone, said Carmia Borek, a professor of pathology at Columbia University College of Physicians and Surgeons. “The question is, how much is too much?”

Borek, lead author of a report in the journal Carcinogenesis, said the experiment was conducted on hamster and mouse cells, the same technique used in other carcinogen studies where results later were extended to humans.

Ozone is the gas that forms a layer 10 to 20 miles high in the stratosphere, where it has the protective effect of blocking much of the sun’s ultraviolet radiation. But close to the ground it can cause breathing difficulties, chest pains, eye irritation and headaches.