Carboxylesterase activity is a potential tool for detecting the presence of insecticides and monitoring of organism exposure to insecticides. Carboxylesterases are a/b-hydrolase fold enzymes that hydrolyze esters to the corresponding acid and alcohol, a process that generally results in products of decreased toxicity and increased polarity (i.e., water solubility). One of the major routes of pyrethroid, organophosphate (OP) and carbamate detoxification is via carboxylesterase-mediated metabolism. Accordingly, the use of carboxylesterase activity has been proposed in a range of environmental monitoring applications. We are interested in two main applications of carboxylesterase activity in environmental monitoring: 1) the use of carboxylesterase activity as a biomarker of insecticide exposure and 2) the use of carboxylesterase addition in Toxicity Identification Evaluations (TIEs) to detect pyrethroid-associated toxicity.

TIEs are standardized methods designed to characterize, identify and confirm the cause of toxicity in water and sediment. One of the challenges in TIEs and environmental monitoring methods is the selective detection of pyrethroids. Current TIE techniques have been adapted for pyrethroid identification, but there are a number of issues related to method selectivity. Carboxylesterase addition removes pyrethroid-associated toxicity in a dose-dependent manner and does not compromise the toxicity of other insecticides, such as OPs, suggesting that carboxylesterase treatment will not interfere with standard OP identification protocols. Carboxylesterase activity has been successfully employed in TIEs for detecting pyrethroid-associated toxicity.

Carboxylesterase activity has also been proposed as an endpoint measurement for organism exposure to OPs and/or carbamates, with some data suggesting that it is a more sensitive endpoint then acetylcholinesterase activity. Accordingly, we are interested in the application of carboxylesterase activity as a biomarker of insecticide exposure in a range of organisms.