Researchers at the National Institute of Environmental Health Sciences assessed pesticide and other occupational exposures as risk factors for adult-onset asthma in more than 25,000 farm women in North Carolina and Iowa. They found an average increase of 50 percent in the prevalence of allergic asthma in all farm women who applied or mixed pesticides.

Some rarely used compounds such as parathion were associated with almost a three-fold increase in allergic asthma. But even some commonly used pesticides, such as Malathion, were associated with a marked increase in allergic asthma prevalence, the American Thoracic Society said Friday in a release.

Permethrin, used in consumer items such as insect-resistant clothing and anti-malaria bed-nets, was associated with both allergic and non-allergic asthma, the report said.

The study was published in the American Journal of Respiratory and Critical Care Medicine.