Using Mutations for Pesticide Resistance to Identify the Cause of Toxicity in Environmental Samples

Area of Science:

• Environmental toxicology
• Ecotoxicology
• Aquatic toxicology

Background:

• Traditional Toxicity Identification Evaluations (TIE) rely on physical or chemical sample manipulation.
• Pesticide resistance mutations in aquatic organisms offer a novel, biologically based TIE approach.
• Hyalella azteca populations from pesticide-affected areas exhibit significant resistance to common pesticides.

Purpose of the Study:

• To develop and validate a biologically based TIE using pesticide-resistant Hyalella azteca.
• To identify specific toxicants in environmental runoff samples.
• To demonstrate the specificity of resistance mutations for causal agent identification.

Main Methods:

• Collected Hyalella azteca populations from pesticide-affected waterways and laboratory-cultured strains.
• Exposed both resistant and nonresistant H. azteca to urban and agricultural runoff samples.
• Utilized differential toxicity responses between resistant and nonresistant individuals to infer toxicant identity.

Main Results:

• Pyrethroid-resistant H. azteca showed no adverse effects from runoff samples that were lethal or paralyzing to nonresistant individuals.
• This differential response strongly implicated a pyrethroid as the causative agent in the tested runoff.
• Lack of toxicity to pyrethroid-resistant, but chlorpyrifos-sensitive, individuals ruled out chlorpyrifos as a primary toxicant.

Conclusions:

• Biologically based TIE using pesticide-resistant organisms is a powerful tool for identifying specific environmental toxicants.
• Pesticide resistance mutations provide a highly specific biomarker for pinpointing causal agents.
• This method holds potential for broader application with strains resistant to various toxicants.