Technical Bulletin No. 0972: Using Monte Carlo Analysis to Characterize the Uncertainty in Final Acute Values Derived from Aquatic Toxicity Data

Many ambient water quality criteria established to protect aquatic life from acute toxicity are calculated using a procedure described in the U.S. Environmental Protection Agency's 1985 guidelines. The procedure yields a final acute value (FAV) from acceptable LC50 or EC50 concentrations that is a single point, deterministic estimate of the concentration of a chemical substance that will protect 95% of aquatic species from > 50% mortality or other acute toxic effects. However, because of variation and uncertainty associated with toxicity test results, uncertainty in the estimated FAV exists that is not accounted for by the 1985 guidelines procedure. Here, Monte Carlo analysis is used to characterize this uncertainty.