Filtered air cuts down mutations.

Here's another possible reason to be concerned about airborne particulates: The microscopic particles cause heritable mutations by damaging the DNA of cells that give rise to sperm, according to a study of mice exposed to air pollution near an industrial site.

Soot and other particulates of various sizes have previously been linked to an array of health problems, including asthma and heart attacks (SN: 8/2/03, p. 72). One sign of possible genetic damage showed up about a decade ago, when James S. Quinn of McMaster University in Hamilton, Ontario, found an abnormally large number of mutations in herring gulls nesting near steel mills. In 2002, he and his colleagues reported that laboratory mice raised near the same mills also had more mutations in their eggs and sperm, or germ cells, than ones raised in rural areas did. The researchers didn't discern whether gases, such as sulfur dioxide, or particulates were to blame.

In its latest mouse study, Quinn's group performed the same comparison of germ cell-mutation rates but added groups of mice breathing the local air filtered of particulates but not gases.

In the May 14 Science, Quinn and his colleagues report more germ-cell mutations in the mice raised in an industrial setting than in those raised in a rural environment. However, the mutation rate for animals getting filtered air near the mills was comparable to that of the groups raised at the rural site.

This indicates that it's particulates in the air, not gases, that are doing the DNA damage, the researchers conclude.

The mutations observed occur in so-called marker-DNA sequences, which have no apparent biological role, so it's not clear that the particulates are also damaging genes related to the animals' health, cautions Quinn.--J.T.