Estrogenic endpoints in fish early life-stage tests: luciferase and vitellogenin induction in estrogen-responsive transgenic zebrafish.

This study incorporated specific endpoints for estrogenic activity in the early life-stage (ELS) test, as described in Guideline 210 of the Organization for Economic Cooperation and Development and traditionally used for toxicity screening of chemicals. A transgenic zebrafish model expressing an estrogen receptor-mediated luciferase reporter gene was exposed to ethinylestradiol (EE2), and luciferase activity as well as vitellogenin (VTG) was measured. Concentrations of EE2 were tested at 1, 3, or 10 ng/L for 30 d from fertilization or during only the last 4 d with dimethylsulfoxide (DMSO) as presolvent (0.01%). Exposure to EE2 induced no toxic effects. Mean body weights were significantly higher in groups exposed for 30 d in the presence of DMSO, but condition factors were not affected. Significant luciferase and VTG induction occurred following 30-d exposure (3 and 10 ng EE2/L), while only VTG levels were affected in the 4-d exposure (10 ng EE2/L). This study demonstrated the usefulness of incorporating estrogenic endpoints in the OECD ELS test, fitting the requirements for screening estrogenic activity of chemicals. Quantitative measurement of both VTG and luciferase activity proved to be rapid and sensitive. Additional value of using transgenic zebrafish lies in combining VTG measurement with the more mechanistic approach of luciferase induction in one experiment.

Responses in sediment bioassays used in the Netherlands: can observed toxicity be explained by routinely monitored priority pollutants?

In order to identify the cause of toxicity in sediments and suspended matter, a large number of samples with different degrees of contamination was taken at various locations in The Netherlands. Standard acute bioassays were carried out with the bacterium Vibrio fischeri, the rotifer Brachionus calyciflorus and the anostracan Thamnocephalus platyurus. Chronic standard tests were performed using the water flea Daphnia magna and larvae of the midge Chironomus riparius. Some novel bioassays were performed as well. Most toxic effects observed in standard bioassays with sediments from polluted sediments (class 3 and 4 on a scale of 0-4 according to the Dutch criteria) could be partly explained by toxic concentrations of known persistent priority pollutants, mainly heavy metals and occasionally polycyclic aromatic hydrocarbons. In some of the samples, ammonia toxicity was a confounding factor during testing. Suspended matter from the Meuse river at Eijsden, which may be considered as 'new' sediment (pollution class 2), was moderately to highly toxic in almost all bioassays. This could have been associated with a combination of heavy metals, PAHs and ammonia. At two locations from the Lake IJssel area with no apparent persistent pollution, moderate and strong effects were nonetheless observed in invertebrate tests. This might have been due to agricultural run-off of pesticides, which are not routinely measured in sediments. A few effects on V. fischeri in canals and a small stream could not be explained with standard chemical analysis, but seemed associated with the outlets of sewage water treatment plants and industrial effluents. Additional chemical analysis of pore water samples from five selected sediments yielded more identified substances such as phtalates, decanes, cosanes and fragrances, but it was estimated that their contribution to the effects observed on V. fischeri, D. magna and C. riparius was negligible.