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Toxicant- and response-specific comparisons of statistical methods for estimating effective concentrations
M R Hughes1, A J Bailer, D L Denton
1Center for Environmental Toxicology and Statistics, Miami University, Oxford, Ohio 45056, USA. hughesmr@muohio.edu
Environmental Toxicology and Chemistry
|June 8, 2001
Summary
A new statistical method, the relative inhibition concentration estimator (RIp), offers improved toxicity estimation in environmental assessments compared to standard U.S. EPA methods. RIp can estimate toxicity when traditional methods fail, particularly with hormesis effects.
Area of Science:
- Environmental Science
- Ecotoxicology
- Statistical Modeling
Background:
- Standard U.S. Environmental Protection Agency (U.S. EPA) methods for whole effluent toxicity tests estimate concentrations causing specific inhibition levels.
- Current U.S. EPA methods include linear interpolation and probit-based approaches.
Purpose of the Study:
- To compare the performance of standard U.S. EPA toxicity estimation methods with a new parametric regression-based estimator, the relative inhibition concentration estimator (RIp).
- To evaluate the RIp estimator's applicability to chronic toxicity data from U.S. EPA Region 9 reference toxicity tests.
Main Methods:
- The relative inhibition concentration estimator (RIp) was applied with a 25% inhibition level to chronic toxicity data.
- Data included marine species (red abalone) and freshwater species (fathead minnow) exposed to various reference toxicants.
- Statistical correlations and estimability of RIp versus U.S. EPA estimators were analyzed.
Main Results:
- RIp and U.S. EPA estimators showed high correlation for red abalone but variable correlation (0.67-0.99) for fathead minnow, depending on the toxicant.
- RIp was estimable in cases where standard U.S. EPA methods failed, often due to enhanced responses like hormesis.
- Lab-to-lab variability was low for red abalone but high for fathead minnow.
Conclusions:
- The RIp method provides a robust alternative to standard U.S. EPA estimators, especially when dealing with complex biological responses.
- RIp's ability to account for hormesis and other enhanced responses enhances its utility in toxicity testing.
- The RIp method improves the reliability of toxicity estimations in environmental monitoring.