Effects of aged TiO2 nanomaterial from sunscreen on Daphnia magna exposed by dietary route.

The toxicity of dietary exposure to artificially aged TiO(2) nanomaterial (T-Lite™) used in sunscreen cream was studied on D. magna. Pseudokirchneriella subcapitata cultures were contaminated with TiO(2)-residues, obtained by artificial aging. Significant association of TiO(2)-residues on algae was detected by X-ray fluorescence spectromicroscopy. A D. magna dietary chronic exposure of these contaminated algae with TiO(2)-residues was performed. X-ray chemical imaging revealed that Ti was localized only in the digestive tract of the daphnia. Chronic exposure of daphnia to by-product of aged TiO(2) nanoparticles brought by food induced low mortality but decreased growth and reproduction which can be partly related to the modification of the digestive physiology of daphnia. This study demonstrated that the assessment of the ecotoxicological impact of nanomaterials in aquatic environment should take into account the aging of these materials which can further influence their bioavailability for aquatic organisms.

In vivo proton HR-MAS NMR metabolic profile of the freshwater cladoceran Daphnia magna.

The method concerning in vivo proton HR-MAS NMR metabolic profiling of the freshwater cladoceran Daphnia magna is presented. Viability tests of D. magna under different spinning rates were performed. All surviving daphnids after analysis have developed eggs and embryos like control animals. Better survival rate at the slowest rotation speed were observed. The maximum length of analysis during which the integrity of the daphnid is maintained was assessed. The recorded proton spectra of in vivo daphnia were attributed to lipids from the triglycerol category. Saturated and unsaturated omega-3 like fatty acid moieties of triacylglycerol were well identified. The relationship between physiological state of daphnids and lipid profile are discussed.

Toxicity of ivermectin on cladocerans: comparison of toxic effects on Daphnia and Ceriodaphnia species.

Interspecies differences in contaminant sensitivity are measured to assess environmental risk based on species sensitivity distribution. The present study was intended to demonstrate the importance of studying the effects of contaminants on the life-history traits of various species. To do this, we compared the effects of ivermectin on the survival, growth, and reproduction of two cladoceran species (Daphnia magna and Ceriodaphnia dubia) and two strains of D. magna (one Japanese and one European). Ivermectin is widely used against endo- and ectoparasites in livestock and pets and is known for its high toxicity. Local aquatic ecosystems can be contaminated due to direct excretion into surface waters, but few data are available about the chronic effects of ivermectin on aquatic organisms. Adult daphnids were exposed to concentrations from 0 to 1 ng/L. Our results show a significant effect on all the life-history traits measured and reveal inter- and intraspecies differences. The no-observed-effect concentration found for growth and reproduction is 0.0003 ng/L for D. magna versus 0.001 ng/L for C. dubia, and the lowest-observed-effect concentration is 0.001 ng/L for D. magna versus 0.01 ng/L for C. dubia. C. dubia is smaller than D. magna and appeared to be less sensitive to ivermectin. The European strain of D. magna exhibited less resistance than the Japanese strain. A bias in the sex ratio was observed for all strains tested.

Effects of chronic dietary and waterborne cadmium exposures on the contamination level and reproduction of Daphnia magna.

Regulatory assessments of metal toxicity on freshwater organisms assume that toxic effects are caused by dissolved metals. In aquatic systems, organisms are exposed to both dissolved and particulate-bound metals. In this study, the chronic toxicity of dietary cadmium (Cd) on the reproduction and Cd body burden of Daphnia magna was investigated. Daphnids (<24 h) were successively exposed to dissolved Cd (8 h) and then to uncontaminated or contaminated algae (16 h) for 21 d. The results show a higher Cd burden in daphnids because of the addition of contaminated food and reveal that Cd uptake by D. magna from water and food was additive for the lowest Cd concentrations tested. Similar Cd distributions (cytosolic and insoluble fractions) were observed in the two groups of organisms, showing similar potential toxicity of Cd accumulated from the two exposure routes. Dietary Cd induces deleterious effects on D. magna reproduction. On the basis of Cd body burden of daphnids, the results support the claim that waterborne and dietary Cd exposures were additive in causing toxicity for Cd concentrations lower than 25 microg/L. At the highest Cd concentrations, the importance of dietary Cd on the daphnid contamination level decreases and confounding factors such as feeding rate reduction seem to appear, which induce an effect on neonate reproduction. In this study, we illustrate the need to take the dietary pathway into account in regulatory assessments and to establish effective concentrations with particulate-bound metals.

Effects of the parasiticide ivermectin on the cladoceran Daphnia magna and the green alga Pseudokirchneriella subcapitata.

Although widely used for the treatment of endo- and ectoparasites in livestock and pets, very few data on chronic effects on aquatic organisms are available for the parasiticide ivermectin. In the present study, toxicity of ivermectin to two freshwater organisms, the cladoceran Daphnia magna and the green alga Pseudokirchneriella subcapitata was investigated. For D. magna, a mean LC(50) 48 h of 5.7 ngl(-1) was derived from 10 acute tests. Chronic toxicity of ivermectin to D. magna was extremely high: with 0.001 and 0.0003 ngl(-1), respectively, nominal LOEC and NOEC based on growth and reproduction were far below the analytical limit of detection for this compound. P. subcapitata was considerably less sensitive to ivermectin than D. magna. For both growth rate and yield, EC(50) was >4,000 microgl(-1), LOEC was 1,250 microgl(-1) and NOEC 391microgl(-1). In view of the high toxicity to D. magna, the use of ivermectin might pose a risk to local aquatic ecosystems. Further studies should be carried out to investigate the effects of ivermectin and its degradation products on pelagic and benthic freshwater invertebrates.

Environmental risk assessment of six human pharmaceuticals: are the current environmental risk assessment procedures sufficient for the protection of the aquatic environment?

In this study, exposure and ecotoxicity data of six human pharmaceuticals (carbamazepine, clofibric acid, diclofenac, ofloxacin, propranolol, and sulfamethoxazole) were collected, including our own experimental data and literature data. From this data collection, the two-tiered European draft guideline on the environmental risk assessment of human pharmaceuticals was tested. Measured environmental concentrations in effluents from France and in effluents and surface waters from Germany were compared to the predicted environmental concentrations (PECs) in both countries. In a similar manner, predicted no-effect concentrations (PNECs) derived from acute data and PNECs derived from chronic data were estimated for each pharmaceutical and corresponding PEC/PNEC ratios then were compared in both countries. Globally, results demonstrated that all environmental concentrations (predicted or measured) for each considered pharmaceutical exceeded the 10-ng/L cutoff value, which requires the implementation of the second-tier assessment based on ecotoxicity data. Moreover, the six pharmaceuticals showed a relatively limited acute toxicity, and carbamazepine and propranolol were inaccurately identified as having negligible risks under the current European draft procedure. Such results lead to discussion of the actual procedure on pharmaceuticals, especially on the need of appropriate ecotoxicity tests.

Using a biology-based model (DEBtox) to analyze bioassays in ecotoxicology: opportunities and recommendations.

The conventional analysis of bioassays does not account for biological significance. However, mathematical models do exist that are realistic from a biological point of view and describe toxicokinetics and effects on test organisms of chemical compounds. Here we studied a biology-based model (DEBtox) that provides an estimate of a no-effect concentration, and we demonstrated the ability of such a model to adapt to different situations. We showed that the basic model can be extended to deal with problems usually faced during bioassays like time-varying concentrations or unsuitable choices of initial concentrations. To reach this goal, we report experimental data from Daphnia magna exposed to zinc. These data also showed the potential benefit of the model in understanding the influence of food on toxicity. We finally make some recommendations about the choice of initial concentrations, and we propose a test with a depuration period to check the relevance and the predictive capacity of the DEBtox model. In our experiments, the model performed well and proved its usefulness as a tool in risk assessment.