"When a pesticide's toxic effect takes more than four days to appear, it raises serious concerns about making regulatory decisions based on standard four-day tests for any organism," Relyea said. "For most pesticides, we assume that animals will die during the period of exposure, but we do not expect substantial death after the exposure has ended. Even if EPA regulations required testing on amphibians, our research demonstrates that the standard four-day toxicity test would have dramatically underestimated the lethal impact of endosulfan on even this notably sensitive species."
Andrew Blaustein, a professor in Oregon State University's nationally ranked Department of Zoology, who is familiar with the Pitt study, said the results raise concerns about standards for other chemicals and the delayed dangers that might be overlooked. Some of the frog eggs the Pitt team used had been collected by Blaustein's students for an earlier unrelated experiment, but he had no direct role in the current research.
"The results are somewhat alarming because standards for assessing the impacts of contaminants are usually based on short-term studies that may be insufficient in revealing the true impact," Blaustein said. "The implications of this study go beyond a single pesticide and its effect on amphibians. Many other animals and humans may indeed be affected similarly."
Tadpoles in the Pitt project spent four days in 0.5 liters of water containing endosulfan concentrations of 2, 6, 7, 35, 60, and 296 parts-per-billion (ppb), levels consistent with those found in nature. The team cites estimates from Australiawhere endosulfan is widely usedthat the pesticide can reach 700 ppb when sprayed as close as 10 meters from the ponds amphibians typically call home and 4 ppb when sprayed
|Contact: Morgan Kelly|
University of Pittsburgh