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Pesticide risk to amphibians and reptiles examined

Amphibians and reptiles are the two vertebrate taxa with the highest numbers of endangered species. Environmental pollution from human activities is one of the main threats to these organisms, but they are not considered in risk assessments of pollutants such as pesticides.
Pesticide risk to amphibians and reptiles examined
The aim of the HERPESTI (Characterizing the risk of pesticide use on amphibian and reptile populations based on multiple, ecologically relevant responses) project was to test the degree of protection that European legislation confers to amphibians and reptiles, known collectively as ′herps′.

This was achieved by identifying the impact of pesticides on herp population status and viability, such as reproductive behaviour, immune response and pathogen resistance. The project also determined whether risk assessment protocols are effective in protecting amphibians and reptiles from pesticides.

Researchers studied the risk of exposure of amphibians and reptiles to pesticides using palmate newts (Lissotriton helveticus) and wall lizards (Podarcis muralis). Results indicated a high potential for exposure, both by direct spraying or by uptake through the skin or by feeding. Compared to birds and mammals, herps would stay exposed during long periods of time because of their low chances of moving away from treated areas.

The different ways amphibians and reptiles are exposed to pesticides in the aquatic and terrestrial environments were compared in common frogs (Rana temporaria), palmate newts and wall lizards. It was found that toxicity can depend on the exposure route to certain pesticides, for example the herbicide glufosinate ammonium was more toxic to larval newts when in sediments rather than water. This showed that for aquatic amphibians the ingestion of contaminated food and/or sediments may be a relevant way of pesticide uptake.

Toxicity data based on fish, birds or mammals was assessed for its effectiveness to protect herps from the impact of pesticides. Neglecting amphibians and reptiles in risk assessment is worrying because both groups exhibit particular mechanisms that make them especially vulnerable to the impact of pesticides.

For example assimilation of pesticides through the skin in the terrestrial environment is ignored in tests using mammals and birds. However, the permeable nature of the amphibians skin or the link between reptiles and soil, especially during egg-laying, where the pesticides are applied make this route a significant way of exposure for these creatures.

HERPESTI showed a clear need for reconsidering the way pesticide risk assessments are conducted for vertebrates. It provided evidence that indicated that exposure pathways currently used for fish, birds and mammals are not appropriate for covering the risks to amphibians and reptiles in a significant way.

Related information

Keywords

Amphibians, reptiles, herps, risk assessment, pesticides, HERPESTI, toxicity, sediments, glufosinate ammonium
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