Pollution Alters DNA in Mice, Study Finds



ASHINGTON - Breathing soot from factories or highways may cause genetic damage that can be passed to offspring, scientists have found in an experiment on mice.

It is unclear whether the pollution-damaged DNA harms health. But the discovery comes as scientists already are calling for more research into the dangers of particulates, microscopic soot particles linked to asthma, heart disease and other health problems.

"At the moment, we are grappling with the fact that even though the air is visibly cleaner, we're still finding adverse health effects," said Dr. Jonathan Samet of Johns Hopkins University, who led a recent National Academy of Sciences study of the issue. "The new work now adds another area of potential concern."

Until 2002, there was little evidence that any air pollutant might cause genetic damage that can be inherited.

That year, Canadian scientists placed mice downwind from steel mills and tested their offspring. The males passed on twice as many DNA mutations as did mice living in the cleaner countryside. Those same researchers, who are from McMaster University in Ontario, reported in the journal Science last week that the cause of the mutations was airborne particulate matter, or soot. It is emitted from factories, power plants and diesel-powered vehicles.

In the latest experiments, the scientists housed two groups of mice near the steel mills for 10 weeks. One group breathed outside air; the other was housed in a chamber equipped with high-efficiency air filters to catch microscopic particles.

Then, the mice were bred and scientists checked their offspring for specific DNA mutations that are passed through the father's sperm. The mice breathing filtered air had mutation rates 52 percent lower than those exposed to full-strength pollution, the scientists found.

The mutations measured are not linked to disease, but they are similar to a type of DNA damage that is. Dr. James Quinn, a McMaster biologist and the report's lead author, said more research was needed to determine whether these changes were a marker for potential health problems and whether the mutations could be inherited, too.

Dr. Quinn said the study's practical value might lie in what it showed about the effectiveness of air filtration. Because particulates adhere to tree leaves just as they do to filters, he said, the study may have implications for policy-makers who must decide on road-building and tree-cutting projects.

The Environmental Protection Agency already has ordered tougher limits on ultrafine particulate pollution because of concern about how it affects the elderly, children and people with respiratory illnesses. In December, the agency plans to announce which parts of the country are not in compliance with these rules.

Dr. Quinn said he did not know whether the particulates themselves or toxic chemicals that attach to them damaged the sperm. But one suspect is a group of particulate-clinging chemicals, polycyclic aromatic hydrocarbons, or P.A.H.'s, some of which are known to be cancer-causing. Air samples showed daily P.A.H. exposure near the steel mills was 33 times as high as in the countryside. But HEPA filtering of the urban air blocked most of those chemicals, the study concluded.

Informant: Teresa Binstock


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