title: An assessment of two-step linear regression and a multifactor probit analysis as alternatives to acute to chronic ratios in the estimation of chronic response from acute toxicity data to derive water quality guidelines.
abstract: In aquatic ecotoxicology, acute to chronic ratios (ACRs) are often used to predict chronic responses from available acute data to derive water quality guidelines, despite many problems associated with this method. This paper explores the comparative protectiveness and accuracy of predicted guideline values derived from the ACR, linear regression analysis (LRA), and multifactor probit analysis (MPA) extrapolation methods applied to acute toxicity data for aquatic macroinvertebrates. Although the authors of the LRA and MPA methods advocate the use of extrapolated lethal effects in the 0.01% to 10% lethal concentration (LC0.01-LC10) range to predict safe chronic exposure levels to toxicants, the use of an extrapolated LC50 value divided by a safety factor of 5 was in addition explored here because of higher statistical confidence surrounding the LC50 value. The LRA LC50/5 method was found to compare most favorably with available experimental chronic toxicity data and was therefore most likely to be sufficiently protective, although further validation with the use of additional species is needed. Values derived by the ACR method were the least protective. It is suggested that there is an argument for the replacement of ACRs in developing water quality guidelines by the LRA LC50/5 method.
authors.affiliation: Unilever Centre for Environmental Water Quality (UCEWQ), Institute for Water Research, Rhodes University, PA Box 94, Grahamstown 6140, South Africa.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Slaughter
authors.forename: Carolyn G
authors.initials: CG
authors.lastname: Palmer
authors.forename: Wilhelmine J
authors.initials: WJ
authors.lastname: Muller
mesh_terms: D000818:Animals; D003247:Conservation of Natural Resources; D017753:Ecosystem; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis / Q000706:statistics & numerical data; D005399:Fishes; D017408:Guidelines as Topic; D007928:Lethal Dose 50; D016014:Linear Models; D011786:Quality Control; D018570:Risk Assessment; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*; D014881:Water Supply / Q000331:legislation & jurisprudence / Q000592:standards
chemical_list: D014874:Water Pollutants, Chemical