Magazine article Science News

Bt-Treated Crops May Induce Allergies

Magazine article Science News

Bt-Treated Crops May Induce Allergies

Article excerpt

Bacillus thuringiensis (Bt), a moth-killing bacterium that farmers use as an insecticide, has been considered nontoxic to all but a few types of insect larvae. It may pose some health risk for people, however. A new study of Ohio crop pickers and handlers finds that Bt can provoke immunological changes indicative of a developing allergy.

With long-term exposure, affected individuals might develop asthma or other serious allergic reactions, notes study leader I. Leonard Bernstein of the University of Cincinnati College of Medicine.

During more than 30 years of use, Bt has exhibited little human toxicity. However, "its potential allergenicity had never been carefully addressed," Bernstein says. So, he studied farm workers before and after fields were sprayed.

In the July ENVIRONMENTAL HEALTH PERSPECTIVES, his team demonstrates Bt's allergenicity. Before the pesticide's application, 4 of 48 crop pickers, about 8 percent, had a positive skin test to Bt, indicating a sensitivity that can lead to an allergy. One month after harvesting Bt-sprayed celery, parsley, cabbage, kale, spinach, and strawberries, half the pickers tested positive. That share climbed to 70 percent within another 3 months.

Workers with less direct exposure proved less likely to develop Bt sensitivity. Of 34 packers who washed and crated Bt-treated crops, just 5, or 15 percent, had positive skin tests after the spraying. Among 44 field hands working 3 miles away from Bt-sprayed fields, only 5, or 11 percent, tested positive. …

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