From fleas to brain tumors.

Hints that certain types of pesticides may play a role in triggering brain cancers--the most common solid tumors in children--have popped up in a number of recent studies. New research now strengthens that association and ties it most closely to sprays and foggers used to treat homes for fleas and ticks.

Janice M. Pogoda of Statology in Truckee, Calif., and Susan Preston-Martin of the University of Southern California in Los Angeles reestablished contact with almost 450 mothers who had taken part in an earlier study of pediatric brain tumors. More than half of them had a child with a brain tumor.

This time, the researchers examined the use of pesticides in the home during pregnancy. Although they asked about a host of pesticides, including those used to exterminate snails, lice, and termites, only flea-and-tick foggers and sprays showed a strong statistical link to children's brain cancer, they report in the just-published November Environmental Health Perspectives.

Among the women who used such products, the likelihood that a child would develop brain cancer increased with the number of pets treated. Risks proved highest among children of women who prepared, applied, or cleaned up these products themselves while pregnant--especially if they had ignored some application instructions.

Overall, prenatal exposures to these products were twice as likely to have occurred in children who developed a brain tumor--and five times as likely in those whose tumor showed up before the age of 5.