From February 19, 2001
Natural Factors
Increase Pesticide Toxicity in Frogs
According to a new study, "Predator-induced stress makes the pesticide carbaryl more deadly to gray treefrog tadpoles (Hyla versicolor)," published in the Proceedings of the National Academy of Sciences indicates that frog tadpoles are likely to be far more sensitive to pesticides than traditional tests have suggested. The study was carried out with very low pesticide contamination levels compared to doses normally required to kill tadpoles.
The authors believe their experiment was more accurate for two reasons. First, traditional tests are too short. Second, they are not representative of the natural environment. To make the experimental set-up more realistic, the authors added a natural predator, the spotted salamander, to the experimental, in such a way that the tadpoles could detect its predator, but could not actually be harmed.
The study, conducted
at the University of Pittsburgh by Rick Relyea, PhD, and Nathan Mills,
PhD, revealed that the combination of the predator stress and the carbamate
insecticide carbaryl made the pesticide 2-4 times more lethal than the
pesticide alone. As the writers of www.ourstolenfuture.org point out,
virtually all toxicity testing for regulatory purposes ignores these realities.
It is highly likely, therefore, that current regulatory science even in
its simplest form (does a pesticide kill) has dramatically underestimated
the impacts of many pesticides.