The study looked at 25,814 farm women in North Carolina and Iowa, more than half of whom applied pesticides. It "found an average increase of 50 percent in the prevalence of allergic asthma in all farm women who applied or mixed pesticides," says Newswise, a research-reporting service.
About 40 percent of the women in the study did not grow up on a farm. Their greater risk of developing asthma from pesticide application is "due to a protective effect that remains poorly understood," Newswise says. "Growing up on a farm is such a huge protective effect it's pretty hard to overwhelm it," said Dr. Jane Hoppin of the National Institute of Environmental Health Sciences and lead author of the study.
The study "found that most pesticides were associated only with allergic asthma, even though non-allergic asthma is generally more common in adults," Newswise reports. "Even some commonly used pesticides were associated with a marked increase in allergic asthma prevalence. Malathion, for example, a widely used insecticide, was associated with a 60 percent increased prevalence of allergic asthma."
Because the study was a cross-section of data collected from physicians' reports in the 1990s, the researchers cannot definitively say that using pesticides causes asthma. They are planning a large-scale study that will better evaluate the linkage. To read or download the current study, click here.