Predicting the bioavailability and toxicity of hydrophobic pesticides using bioassays and a solid phase microextraction approach.

摘要

Pesticides are unique chemical stressors in that they are designed to have biological activity and are intentionally released into the environment in large quantities. Although the use of pesticides has resulted in effective pest control and increased crop production, pesticide use has caused unintended adverse effects on non-target species. Assessing the risk of pesticides is challenging in part due to the complications created by bioavailability issues. Bioavailability is an important factor in risk assessment. Solid phase microextraction (SPME) is an equilibrium partitioning technique that has been successfully used to estimate body residues by measuring the freely dissolved chemical concentration and assessing chemical bioavailability in exposure media. The objectives of this dissertation were to: (1) Investigate if legacy and emerging sediment-associated pesticides are widely distributed in agricultural and urban areas of Illinois, and to evaluate if the pesticides cause acute toxicity to benthic organisms; (2) Evaluate the potential use of SPME fiber to estimate pesticide toxicity and organism body residue in water-only tests; (3) Expand the application of matrix-SPME to estimate bioavailability and toxicity of legacy and emerging pesticides in sediment. The statewide investigation showed that legacy and current-use pesticides in sediment were widely distributed in urban and agricultural waterways from Illinois, USA. There were more toxic urban sites than agricultural sites. The SPME fiber was an effective dose metric to evaluate the toxicity of hydrophobic pesticides to the midge Chironomus dilutus and the amphipod Hyalella azteca, in water and sediment exposures. Equilibrium/equilibrium-equivalent SPME fiber concentrations were related to tissue residues, and significant linear relationships were found between the parent compound in the biota and the SPME fiber concentrations. This result occurred regardless of which chemical was tested, whether biotransformation occurred, or if the chemical reached steady state in the organisms. The equilibrium fiber concentrations of permethrin and sum dichlorodiphenyltrichloroethane equivalents were reduced with an increase in sediment aging time, and this was suggestive of a decrease in freely dissolved pore water concentration and subsequently a decrease in bioavailability. Given the results from this dissertation and other previous work, the SPME fiber could be potentially used as a surrogate for assessing bioavailability and toxicological risk of hydrophobic pesticides to benthic organisms. It may provide an additional line of evidence in weight-of-evidence approaches for assessing the effects of hydrophobic pesticides in environmental risk assessments.