August 18, 2009

Study: EPA pesticide test too short

Scientists say the four-day testing period the U.S. Environmental Protection Agency uses to determine safe levels of pesticide exposure is too short.

The University of Pittsburgh researchers said they found the highly toxic pesticide endosulfan -- a neurotoxin banned in several nations, but still used extensively in U.S. agriculture -- can exhibit a lag effect with the fallout from exposure not occurring until after direct contact has ended.

The team that included lead author Devin Jones, post-doctoral researcher John Hammond and Associate Professor Rick Relyea exposed nine species of frog and toad tadpoles to endosulfan levels expected and found in nature for the EPA's required four-day period, then moved the tadpoles to clean water for an additional four days, Jones said.

Although endosulfan was ultimately toxic to all species, three species of tadpole showed no significant sensitivity to the chemical until after they were transferred to fresh water. Within four days of being moved, up to 97 percent of leopard frog tadpoles perished, along with up to 50 percent of spring peeper and American toad tadpoles.

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.

The study appears in the September edition of the journal Environmental Toxicology and Chemistry.