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Multigeneration tests are very useful for the assessment of long term toxicity of pollutants such as endocrine disruptor compounds. In this study, multigeneration reproduction tests adapted from the ISO standard 11267 were conducted with the Collembola Folsomia candida. Springtails were exposed to artificial soil contaminated with four insect growth regulators (methoprene, fenoxycarb, teflubenzuron, and precocene II) according to two different experimental set-ups. In the first set-up, the parental generation (F0) of Collembola was exposed to a pollutant for 28 days. Juveniles from the F1 generation were transferred to uncontaminated soil for another 28-day period to generate the F2 generation. In the second set-up, the F0 generation was exposed to a pollutant for 10 days before being transferred to uncontaminated soil to reproduce. After 18–28 days, juveniles from the F1 were transferred to clean soil to generate the F2 generation. An effect on the number of hatched juveniles of the F2 generation was observed for methoprene after exposure of the F0 for 28 days and hatching of F1 in contaminated soil. For methoprene and teflubenzuron, significant effects were even observed on the F2 generation with the second experimental set-up, when only the F0 generation was exposed for 10 days. This shows that the impact of these substances is transgenerational, which can have important consequences for the population of these or other organisms. No effect on the F2 generation was observed with fenoxycarb and precocene II with the 10-day exposure experiment. Our results show that the developed experimental procedures are appropriate to assess the long term effects of endocrine disrupting compounds on the reproduction of the non-target species F. candida. Another important finding is that two substances with the same predicted mode of action (i.e., the two juvenile hormone analogues fenoxycarb and methoprene) do not necessarily affect the same endpoints in F. candida. [Copyright &y& Elsevier]

Abstract: Models describing dose–response relationships are becoming increasingly popular in ecotoxicology. They allow simple and thorough evaluations of toxicity test results, including inter- and extrapolations to concentrations or exposure times other than those tested. Simple parametric regression models are of particular interest because their parameters may be attributed mechanistic meanings and they can be applied without sophisticated mathematical and computational support. We recently proposed a four-parameter logistic regression model to fit the survival data of Daphnia magna under dinoseb stress. The model parameters are the maximum survival time, the minimum time required for an individual to die, effect concentration, EC50, and a curve shape parameter. This model has now been applied to compare the lethality and reproduction toxicity of D. magna and the growth inhibition of Pseudokirchneriella subcapitata under dinoseb stress. It can be fitted adequately to all the measured data and the parameters can be attributed biological meanings in any of the three endpoints. A comparison of the modeled concentration–response functions of all three endpoints for dinoseb toxicity shows that the range of ECs with respect to both D. magna and algae is steep (a decrease of between 0.1 and 0.6mg/L). The survival and reproduction of D. magna exhibit similar characteristic concentration–response functions and toxicities. The statistical no-effect concentration (SNEC) is 0.14 (survival) and 0.11 (reproduction)mg/L, respectively. On the other hand, algae seem to be less sensitive to dinoseb than D. magna (SNEC: 0.48mg/L). However, further investigations of individual algae may lead to a more suitable comparison. We speculate that the four parameters of the model function can be related to specific properties of chemicals and organisms. Characterization of these properties would allow simple and appropriate estimation of the toxic effects of these chemicals. [Copyright &y& Elsevier]

Toxicity of sediment from waterways of Ho Chi Minh City (HCMC), VietNam, was assessed in aqueous and organic extracts using the organisms Daphnia magna and Vibrio fischeri. Sediment samples were taken along the main canals of HCMC and in the Saigon river. The results indicate a relatively high potential toxicity of the extracts, especially concerning the aqueous extracts. V. fischeri shows a higher sensitivity than D. magna for both types of extracts. Sediments from the canalsin the urban areas, where the industrial and domestic activities areconcentrated, indicate a higher potential toxicity than sediments from the river. Organic extracts of deep sediments (about 1.3 m) are less toxic than surface sediment. The toxicity of the organic sediment extracts was higher in 1999 than in 1996, except for one site, where dredging operations have been carried out since 1997. The dredging operations thus have a positive local effect on the sediment quality, but further consequences on water and sediment quality of HCMC canals and rivers still have to be evaluated. [ABSTRACT FROM AUTHOR]