Early exposure to common weed killer impairs amphibian d...( MEDFORD/SOMERVILLE Mass. - Tadpoles ...)

MEDFORD/SOMERVILLE, Mass. - Tadpoles develop deformed hearts and impaired kidneys and digestive systems when exposed to the widely used herbicide atrazine in their early stages of life, according to research by Tufts University biologists.

The results present a more comprehensive picture of how this common weed killer once thought to be harmless to animals -- disrupts growth of vital organs in amphibians during multiple growth periods.

In recent years, worldwide amphibian population declines have fueled concerns over the potentially harmful effects of pesticides on "sentinel" organisms. Previous research had revealed negative effects of atrazine on amphibians extremely early and late in development. The Tufts study, published in the February 2008 edition of "Environmental Health Perspectives," examined tadpoles during an often overlooked period of development, organ morphogenesis.

Organ morphogenesis is a brief, extremely sensitive phase in the tadpoles' growth cycle when they are starting to develop organs, noted Kelly A. McLaughlin, Associate Professor of Biology and lead researcher in the study. She explained that experiments were designed to broaden the understanding of how chemicals affect biological growth in amphibians over multiple stages of development. A $5,000 Tufts University Faculty Research Marshall Grant helped fund the study.

"Amphibians are very vulnerable to contamination since atrazine is used in the same environs where they live and breed," McLaughlin said.

Atrazine is used to control broadleaf and grassy weeds on golf courses and residential lawns, according to the Federal Environmental Protection Agency. Farmers use it to treat corn and soybeans. Atrazine blocks photosynthesis once it is absorbed by plants. Chronic exposure to the herbicide during metamorphosis altered amphibian gonadal deve
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