A Review of Inter- and Intralaboratory Effluent Toxicity Test Method Variability

Abstract

Due to the increased emphasis on the use of aquatic toxicity tests to evaluate the quality of complex effluents, there is a need to objectively evaluate the precision of effluent toxicity test methods. Based upon an extensive search of the published and unpublished literature (available through April 1985), the intralaboratory and interlaboratory precision of effluent toxicity test methods was evaluated. Most of the inter- and intralaboratory studies obtained address the acute toxicity of effluents to three standard test organisms: Daphnia spp. (water fleas); Salmo gairdneri (rainbow trout); and the marine bacterium Photobacterium phosphoreum (Microtox). Only limited data exist for Pimephales promelas (fathead minnows); Mysidopsis bahia (opposum shrimp); and Cyprinodon variegatus (sheepshead minnows). Based on LC50 or EC50 values for 141 effluents for which interlaboratory data were available, 81.6% had coefficients of variation ≤40%, and 74.5% had coefficients of variation ≤30%. For 46 effluents for which intralaboratory data were available, 89.2% had coefficients of variation ≤40%, and 89.2% also had coefficients of variation ≤30%. To put this variability in perspective, coefficients of variation for these replicated toxicity tests with effluents are compared to published precision estimates for analytical chemistry methods.

Review on the acuteDaphnia magnatoxicity test – Evaluation of the sensitivity and the precision of assays performed with organisms from laboratory cultures or hatched from dormant eggs

“…Characteristics and major data on the intra-and inter-laboratory studies dealing specifically with acute D. magna tests compiled by Parkhurst et al (1992) have been taken from the compilation review and are presented in Tables I and II respectively. Although according to Parkhurst et al (1992) the most extensive data set available for the test variability of acute tests is for assays with Daphnias (D. magna, D. pulex and Ceriodaphnia dubia), Tables I and II show that the number of intra-and inter-laboratory studies dealing specifically with acute D. magna assays is in fact limited. The data indeed originate from only five studies (Broderius, 1983;Buikema, 1983;Grothe and Kimerle, 1985;Lewis and Weber, 1985;Rue et al, 1988), in which only a limited number of laboratories participated with a limited number of chemicals or effluents. One of the most striking facts of this data compilation is that although all the assays were carried out according to the "standard" prescriptions of the US EPA manuals for toxicity testing, both tables indicate that there is a very broad range between the lowest and the highest variation coefficients for the LC50s or EC50s; the minimum CVs are indeed as low as 0-3% and the maxima are up to 72-143%.…”

Inter- and Intra-Laboratory Testing of the Daphnia magna IQ Toxicity Test™

“…The intra-laboratory variation typically observed for Daphnia spp. tests is less than 20% (Rue et al, 1988). 1 100* * n = 2 for one lab ** n = 2 for two labs These data indicate that the Daphnia magna IQ Toxicity Test™ has an interlaboratory precision in the range of that of the standard 48-hour D. magna bioassay.…”

“…In a review of inter-laboratory data for aquatic toxicity tests, 85% of the CVs for Dahnia spp tests ranged from 050%, with 50% of the tests being within 0 and 20% (Rue et al, 1988). The USEPA (1991) reported CVs of 166% for 12 laboratories exposing D. magna to silver chloride, 51% for 11 laboratories exposing D. magna to endosulfan, and 50% for 11 laboratories exposing Ceriodaphnia dubia to potassium chloride.…”

“…Although during test development, problems with intra-laboratory variation were not observed (unpublished data), inter-laboratory tests have not been reported. Factors which may contribute to inter-and intra-laboratory test precision include organism health, age, test temperature, variations in culture and handling, and feeding (Rue et al 1988). Although controlling these factors would likely increase the precision of any toxicity test, the Daphnia magna IQ Toxicity Test™ was intended to be used in a variety of conditions, with cultured or shipped organisms, and with little or no training.…”

Aquatic toxicity tests for the control of effluent discharges in the UK ? the influence of test precision

“…In addition, an extensive inter and intralaboratory comparison using potassium dichromate and three organic compounds (ISO, 1989; Rue et al (1988) concluded that 90% of tests yielded intralaboratory CVs of less than 30% compared with 79% of interlaboratory comparisons producing this level of precision. With 47 different studies on repeatability and 18 interlaboratory studies, they provide the only real opportunity to compare variability when tests are performed on different occasions within a laboratory, or in different laboratories.…”