Study: Bad Air May Alter Your DNA
Breathing soot from factories or highways may cause genetic damage that can be passed to the next generation, scientists found in an experiment performed on mice.
No one yet knows if people could inherit pollution-damaged DNA that harms their 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" from particulates, said Dr. Jonathan Samet of Johns Hopkins University, who headed a recent National Academy of Sciences probe of the pollutant.
"The new work now adds another area of potential concern" because of the implications for future generations, he said Thursday.
There had been little evidence that any air pollutant might cause the kind of genetic damage that can be inherited - until Canadian scientists in 2002 housed mice downwind from steel mills and tested their offspring. The males passed on double the DNA mutations as mice living in the cleaner countryside.
Those same researchers from Ontario's McMaster University are reporting in the journal Science that they've found the culprit: airborne particulate matter, better known as soot. It is commonly emitted from factories, power plants and diesel-powered vehicles.
In the latest experiments, biologist James Quinn and colleagues 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 HEPA filters - high-efficiency air filters designed 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 experiment showed mice that breathed filtered air had mutation rates 52 percent lower than the mice exposed to full-strength steel mill pollution.
The specific sperm changes measured aren't linked to disease, but they're similar to a type of DNA damage that is. Quinn said more study is needed to see if they're a marker for potential health problems and whether pollution-spurred mutations in disease-causing genes could be inherited, too.
Regardless, Quinn said the study's practical value may be that it demonstrates the effectiveness of air filtration. The HEPA filters blocked particulates, and nature does the same thing - particulates adhere to tree leaves - which has implications for policy-makers who must decide on road-building and tree-cutting projects, he said.
Tiny enough to be inhaled deeply into the lungs, these particulates enter the bloodstream and move through the body. If they can make it all the way downstream to sperm-forming cells, "that would be quite a remarkable sequence" - one that needs confirmation, cautioned Hopkins' Samet.
And the potential for affecting future generations makes it "both a public health issue and an issue for the ecosystem," he said.
The Environmental Protection Agency already has ordered tougher curbs on ultra-fine 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 areas of the country aren't in compliance.
Quinn couldn't say if the particulates themselves or toxic chemicals that attach to them damaged the sperm. But one suspect is a group of particulate-clinging chemicals called polycyclic aromatic hydrocarbons, or PAHs, some of which are known to be cancer-causing.
Air samples showed daily PAH exposure near the steel mills was 33 times as high as in the nearby cleaner countryside, but HEPA filtering of the urban air blocked most of those chemicals as well, the study concluded.
By Lauran Neergaard