“Farm women are an understudied occupational group,” said Jane Hoppin, Sc.D., of the National Institute of Environmental Health Sciences and lead author of the study. “More than half the women in our study applied pesticides, but there is very little known about the risks.” The researchers assessed pesticide and other occupational exposures as risk factors for adult-onset asthma in more than 25,000 farmwomen in North Carolina and Iowa. They used self-reports of doctor-diagnosed adult asthma, and divided the women into groups of allergic (atopic) or non-allergic (non-atopic) asthma based on a history of eczema and/or hay fever.

They found an average increase of 50 percent in the prevalence of allergic asthma in all farm women who applied or mixed pesticides. Remarkably, although the association with pesticides was higher among women who grew up on farms, these women still had a lower overall risk of having allergic asthma compared to than those who did not grow up on farms, due to a protective effect that remains poorly understood. "Growing up on a farm is such a huge protective effect it's pretty hard to overwhelm it," said Hoppin. "But about 40 percent of women who work on farms don't report spending their childhoods there. It is likely that the association with pesticides is masked in the general population due to a higher baseline rate of asthma."

Some legal but rarely used compounds, such as parathion, were associated with almost a three-fold increase in allergic asthma. But 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. “There is a difference in asthma prevalence between women who did and did not use pesticides but whether it is causal or not remains to be seen,” cautions Hoppin.

MEDICA.de; Source: American Thoracic Society (ATS)