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(P378) ACE, Acute-to-Chronic Estimation Software for Windows.
Ellersieck, M*,1, Asfaw, A1, Mayer, F2, Krause, G1, Sun, K1, Lee, G1, 1 University of Missouri, Columbia, Columbia, MO2 U.S. EPA, Gulf Breeze, FL
ABSTRACT- Chronic No-Observed Effect Concentrations (NOEC) are commonly determined by either using acute-to-chronic ratios or by performing an ANOVA on chronic test data; both require lengthy and expensive chronic test results. Acute-to-Chronic Estimation (ACE) software was developed to predict chronic toxicity from raw, acute toxicity test data; it utilizes three different approaches (Accelerated Life Testing, ALT; Multifactor Probit Analysis, MPA; and two-stage Least Square Regression, LSR). All three methods use all time periods (time-to-event) in acute tests to forecast Lethal Concentration (LC) percents. ALT is based on a population-response distribution; time-to-failure (death) of each experimental unit is independent. MPA is a two-dimensional probit analysis using both time and concentration to produce a multiple regression equation. LSR calculates LC values for each time period, regressing LC values as Y and the reciprocal of time as X; Y intercept is interpreted as the chronic value. LSR functions with no partial responses, while ALT and MPA require 3 and 5, respectively. All methods produce confidence intervals for the LC estimates, and the estimates have been shown to be accurate a high percentage of time (LSR = 85-89%, ALT = 74-81%, MPA = 59-74%) when compared to actual chronic test results. The software is written on a Windows platform, providing a user-friendly point and click format. Statistical and software details will be discussed.
Key words: chronic estimation, NOEC, models
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