Bad Air Damages Mouse DNA

Jan. 15, 2008 -- Mice exposed to polluted air have dramatically higher rates of genetic mutations in their sperm than mice that breathe filtered air, according to a study released Monday that suggests airborne pollutants may be linked to inheritable DNA damage.

The study found that mice breathing unfiltered air downwind of two steel mills and a major highway had 60 percent more mutations in their sperm than mice whose air was cleaned with high-efficiency HEPA filters.

For the experiment, the researchers placed two sets of mice downwind of the steel mills and highway in the Canadian city of Hamilton, in Ontario province. One was exposed to the ambient air while the other group of mice had filtered ambient air.

The researchers evaluated them at three weeks and 10 weeks, and while the DNA damage was high in the sperm of the exposed mice, it was largely repaired after six weeks recovery in the lab.

However, when the researchers evaluated a DNA test location known for its high rate of a specific type of DNA damage, known as "tandem repeat" mutations, they found an accelerated rate of mutations in the sperm.

Since the sampled sperm existed as stem cells during the exposure period, and because sperm are known to be well protected from this type of mutation, the researchers conclude that mouse sperm stem cells are vulnerable to particulate air pollution.

"These findings show that chemical pollutants may cause heritable mutation. Further research is required to confirm these results, and to evaluate the potential risk to humans exposed to particulate air pollution," the researchers wrote.

The paper appears in the Proceedings of the National Academy of Sciences (PNAS).

Related Links:

Jen Viegas' blog: Born Animal

How Stuff Works: DNA

Air Quality and Health