title: A comparative study of an accelerated life-test model and a toxicokinetics-based model for the analysis of Porcellio scaber survival data.
abstract: Statistical models have long been used for reliability analysis and risk assessment. In the present study, an accelerated life-test model was used to analyze a set of dose-time-response data obtained with the terrestrial isopod Porcellio scaber. Survival data were experimentally obtained by exposing P. scaber to diazinon (a nonpersistent insecticide) at six concentrations between 2 and 11.31 microg/g (toxicant/soil). Survival data are presented on a weekly basis. The accelerated life-test model assumed a log-normal distribution and constant variance across all diazinon concentrations. Model parameters were obtained by maximum likelihood estimation. The accelerated life-test model was compared to a toxicokinetics-based model reported in the literature. Survival predictions made by both models were compared with the observed data. Both the accelerated life-test model and the toxicokinetics-based model underestimated toxicity at a diazinon concentration of 8 microg/g. Overall, however, the accelerated life-test model outperformed the toxicokinetics-based model, with survival predictions closer to the observed data in most cases and a stronger correlation between predicted and observed survivals. However, as a statistical model, the accelerated life-test model did not reveal mechanistic information, and only statistical and distributional interpretations of its model parameters could be made.
authors.affiliation: Center for Environmental Biotechnology, Department of Statistics, University of Tennessee, 419 Dougherty Engineering Building, Knoxville, Tennessee 37996-2200, USA. sjren@utk.edu
authors.forename: Shijin
authors.initials: S
authors.lastname: Ren
mesh_terms: D000818:Animals; D003976:Diazinon / Q000493:pharmacokinetics* / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005544:Forecasting; D007306:Insecticides / Q000493:pharmacokinetics* / Q000633:toxicity*; D033321:Isopoda / Q000502:physiology*; D015233:Models, Statistical; D018570:Risk Assessment; D012989:Soil Pollutants / Q000493:pharmacokinetics* / Q000633:toxicity*; D016019:Survival Analysis
chemical_list: D007306:Insecticides; D012989:Soil Pollutants; D003976:Diazinon