Fish subchronic toxicity prediction model for industrial organic chemicals that produce narcosis

Abstract

Abstract A model based on partition coefficient was developed for predicting subchronic toxicities of selected chemicals to fish. Early life stage tests were conducted under flow-through conditions using fathead minnows (Pimephales promelas) as test organisms. Embryos, larvae and juveniles were continuously exposed to chemicals for a total of 31 to 33 d. Test endpoints included egg hatchability, incidence of developmental abnormalities, survival and growth. The “chronic value” for each test was a point estimate of the maximum acceptable toxicant concentration (MATC), and was determined as the geometric mean of the highest test concentration producing no effect and the lowest concentration significantly (p ≤ 0.05) affecting one or more endpoints. Ten industrial organic compounds from four chemical classes (ketones, benzenes, ethers and alkyl halides) were used in model development. All chemicals were considered to induce narcosis in fish in acute toxicity tests. The relationship between estimated MATC n-octanol/water partition coefficient (log P) was expressed by the equation log estimated MATC (mol L−1) = -0.886 log P - 2.18 (r2 = 0.925). This model was used to predict subchronic toxicities for eight other alkyl halides and chlorinated benzenes that had been tested with fathead minnows and reported in the literature. The mean ratio for observed chronic toxicity value to predicted chronic toxicity value was 2.00 ± 2.03. Observed values ranged from 0.29 to 6.02 times the predicted values. For the 10 chemicals used in the model, the mean acute/chronic toxicity ratio (96-h LC50/chronic value) was 12.2 ± 8.5.