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Pacific steelhead ( Oncorhynchus mykiss ) exposed to chlorpyrifos: Benchmark concentration estimates for acetylcholinesterase inhibition
Author(s) -
Sandahl Jason F.,
Jenkins Jeffrey J.
Publication year - 2002
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620211126
Subject(s) - chlorpyrifos , acetylcholinesterase , organophosphate , rainbow trout , toxicology , aché , environmental science , detection limit , zoology , pesticide , chemistry , biology , fishery , ecology , fish <actinopterygii> , enzyme , chromatography , biochemistry
Steelhead trout ( Oncorhynchus mykiss ) were exposed for 96 h to the organophosphate chlorpyrifos to establish benchmark concentration (BMC) values in the low‐effect range of brain acetylcholinesterase (AChE) inhibition. The U.S. Environmental Protection Agency (U.S. EPA) benchmark dose software was used to model the data. Benchmark concentrations were determined for a range of inhibition levels at 5, 10, and 20%, at 1 and 2 control standard deviations (SD), and at an experimental limit‐of‐detection level of 2.5%. One contributing difficulty in establishing precise inhibition BMCs in the lower effect region is the variability associated with the AChE analytical method. To minimize this variability, the Ellman method was modified specifically for analysis of O. mykiss brain tissue. Laboratory‐established BMCs for chlorpyrifos were then compared with the U.S. EPA 96‐h water quality criteria and with the concentration levels detected in Northwest surface waters that are home to threatened steelhead trout. The U.S. EPA 96‐h water quality criteria of 0.083 μg/L is below the BMC 02.5 , the limit‐of‐detection value for this study. The average chlorpyrifos concentration detected during a two‐week period in one monitored stream was 0.127 μg/L, which approaches the BMC 02.5. The peak chlorpyrifos concentration detected at 0.482 μg/L is near the BMC 1SD estimate.