Eric Thybaud

Fate and biological effects of lindane and deltamethrin in freshwater mesocosms

Abstract Two freshwater mesocosms (10 and 20 m 3 ) were sprayed with lindane and deltamethrin, respectively. We determined the time-dependent changes in pesticide concentration in water, sediment, macrophyte and gastropod samples and the effects on phytoplanktonic, periphytic and insect communities. Lindane residues persisted 19 weeks in water, 18 weeks in sediment, 14 weeks in macrophytes and 13 weeks in gastropods. Lindane had only transitory effects on periphytic and insect communities, resulting in a slight increase in periphyton ash-free dry weight and a moderate reduction of the number of captured insects. Deltamethrin residues persisted in water for only 96 h. Residues were detected in the macrophyte samples for 5 weeks after treatment but never in the sediment and only 24 h after treatment in the gastropod samples. The phytoplanktonic and periphytic communities were positively affected by the treatment whereas emerging insect abundance was strongly reduced. The presence of the control mesocosms as a source of fauna significantly enhanced the re-establishment of the insect community in the treated mesocosms.

Evaluation of an in vitro hsp70 induction test for toxicity assessment of complex mixtures: comparison with chemical analyses and ecotoxicity tests

The aim of this study was to assess the potential of a human cell line containing the hsp70 promoter linked to the chloramphenicol acetyltransferase reporter gene in evaluating the toxic potential of complex mixtures. Cells were exposed to eluates of industrial wastes and the cellular responses were compared with the metal contents of the samples and with standardized aquatic (microalgal growth inhibition, daphnia Immobilization, bacterial luminescence inhibition, Ceriodaphnia dubia reproduction inhibition) and terrestrial (earthworm lethality, plant growth inhibition) tests. The hsp70 promoter was significantly induced by 11 of 14 samples, with different dose-response patterns. Significant correlations of in vitro induction potency with aquatic ecotoxicity, especially with chronic tests, and with the metal contents of the samples were observed. Our study provides new information on the relevance of hsp70 gene induction as a criterion of toxicity and suggests its usefulness for the detection of toxicity associated with metallic pollution in complex mixtures.

Environmental risk assessment : a critical approach of the European TGD in an in situ application

The aim of this study was to test field relevance of the prospective methodology for the assessment of environmental risk described in the EU technical guidance document (TGD) [European Commission 2003. Technical guidance document in support of Commission Directive 93/67/EEC on Risk assessment for new notified substances and Commission Regulation (EC) No 1488/94 on Risk assessment for existing substances and Commission Directive (EC) 98/8 on biocides, second ed. European Commission, Luxembourg, Part 1, 2 and 3, 760 pp.]. To achieve this goal, an environmental risk assessment was performed according to the TGD for two major contaminants, atrazine and diuron, that are present in the Seine River estuary (France) and listed in the EU Water Framework Directive (Directive 2000/60/CE). Results showed that atrazine presented a source of risk in the upper- and mid-estuary throughout the 1993 and 1996 spring seasons. Diuron introduced a risk into the same areas throughout spring periods of 1993-2005. Results are discussed and some suggestions for a more realistic in situ risk assessment are given. For the computation of a more relevant PNEC for pesticides, their specific mode of action should be taken into consideration as well as ecotoxicological data on species endemic to the considered area.

Uptake and elimination of lindane by Lymnaea palustris (mollusca: Gastropoda): A pharmacokinetic approach

The uptake and elimination of lindane by adult Lymnaea palustris (Müller) were studied using a static contamination system. First-order one- and two-compartment models were used to quantitatively describe these phenomena. The accumulation of residues was triphasic and the observed steady-state bioconcentration factor lay between 36.8 and 56.4 but did not significantly depend on the initial lindane concentration (6, 60, and 600 micrograms liter-1). Accumulation was inferior to that observed for other aquatic organisms and this was attributed to the relatively low lipid content of L. palustris tissues (mean of 0.81 +/- 0.17% of fresh weight). The transfer of snails to lindane-free water after 72 hr of exposure was followed by a biphasic elimination of residues with a half-life of 0.7 hr in the central compartment and of 130.2 hr in the peripheral compartment. Additional experiments showed that the residues enter the snails through the foot and are afterward stocked within the visceral mass which contains approximately three times more lipids than the foot (1.03 +/- 0.13% of fresh weight vs 0.37 +/- 0.03%).

Interspecies Correlations for Predicting the Acute Toxicity of Xenobiotics

LD50 tests on rat and mouse are commonly used to express the relative hazard associated with the acute toxicity of new and existing substances. These tests are expensive, time consuming, and actively fought by Animal Rightists. Consequently, there is a need to find alternative methods. If the design of QSAR models can be used as surrogate, the search for interspecies correlations also represents a valuable alternative to the classical mammalian laboratory tests. In this chapter, the different toxicity​ = ​ f(ecotoxicity) models available in the literature were first critically analyzed. In a second step, a strong bibliographical investigation was performed to collect oral, intraperitoneal, and intravenous rat and mouse LD50 data for a large collection of structurally diverse chemicals. In the meantime, EC50 data on Vibrio fischeri (MicrotoxTM test) and Daphnia magna were also retrieved from literature. Numerous oral, intraperitoneal, and intravenous rat and mouse toxicity models were derived using Vibrio fischeri and Daphnia magna as independent variables alone or together through a stepwise regression analysis. Most of the models on Daphnia magna were totally new and some of them presented acceptable quality. They outperformed the MicrotoxTM models. The usefulness of the 1-octanol/water partition coefficient (log P) as additional independent variable was also tested. The interest of nonlinear statistical tools for deriving toxicity​ = ​ f (ecotoxicity) models was also experienced.

Toxicological Models Part B: Environmental Models

Assessment of ecotoxicological risks due to chemical substances is based in part on establishing concentration–response relationships for different organisms, including plants, invertebrates, and vertebrates living on land, fresh water, or sea water. European regulations for assessing the risks due to chemical products thus recommend the measurement of toxic effects on at least three taxons (algae, crustacea, fish) [1]. The assessment becomes more relevant when based upon a variety of different organisms, with a range of different biological and ecological features (autotrophic or heterotrophic, benthic or pelagic habitat, and different modes of reproduction, growth, respiration, or feeding, etc.), but also when it describes the effects of contaminants on sensitive physiological functions such as growth and reproduction, which determine the balance of populations of terrestrial and aquatic species in their environment.