Concentrations of the 10 most popular pesticides that fall within EPA safe-exposure levels, when combined, cause 99 percent mortality in Leopard Frog tadpoles.
PITTSBURGH—Ten of the world’s most popular pesticides can decimate amphibian populations when mixed together even if the concentration of the individual chemicals are within limits considered safe, according to University of Pittsburgh research published Nov. 11 in the online edition of Oecologia. Such “cocktails of contaminants” are frequently detected in nature, the paper notes, and the Pitt findings offer the first illustration of how a large mixture of pesticides can adversely affect the environment.
Study author Rick Relyea, an associate professor of biological sciences in Pitt’s School of Arts and Sciences, exposed Gray Treefrog and Leopard Frog tadpoles to small amounts of the 10 pesticides that are widely used throughout the world. Relyea selected five insecticides—carbaryl, chlorpyrifos, diazinon, endosulfan, and malathion—and five herbicides—acetochlor, atrazine, glyphosate, metolachlor, and 2,4-D. He administered the following doses: each of the pesticides alone, the insecticides combined, a mix of the five herbicides, or all 10 of the poisons.