Last Updated: 2009-12-28 12:31:04 -0400 (Reuters Health)
By Joene Hendry
NEW YORK (Reuters Health) - Farmers might breathe a little easier after learning that pesticide use does not appear to increase their risk for developing asthma - as long as they wear protective equipment and don't have periods of unusually high exposure.
Farmers need to "handle chemicals carefully and cautiously," Dr. Jane Hoppin, at the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina, cautioned in an email to Reuters Health.
She and her team found that overall pesticide use - that is, the number of years the farmers had worked with pesticides - had no effect on their risk for developing asthma as adults. But what did affect farmers' risk was what the researchers called "high pesticide exposure events."
Farmers who inhaled pesticides during periods of particularly high exposure were nearly twice as likely to develop adult-onset asthma as farmers who never had high-exposure periods, Hoppin and colleagues report in the European Respiratory Journal.
But, because the study assessed pesticide exposure and asthma at the same time, "we can't know which came first," Hoppin said.
Hoppin and her team studied 19,704 men -- mostly farmers and all licensed pesticide appliers -- who reported how often and how long they had used 48 different farm pesticides by the time they enrolled in the Agricultural Health Study (between 1993 and 1997).
About 2 percent of the men had been diagnosed with asthma for the first time when they were 20 years of age or older, including 127 with allergic asthma and another 314 with non-allergic asthma.
Twelve pesticides were linked with a higher risk for adult-onset allergic asthma, and four were linked with non-allergic asthma.
And while the total duration of exposure to all the pesticides overall was not linked with adult-onset asthma, for some of the pesticides there did seem to be an association between lifetime days of use and asthma risk.
Hoppin and colleagues are continuing to observe this same group of farmers to better assess whether their chemical exposures preceded the disease.
SOURCE: European Respiratory Journal, December 2009.