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Pesticides are toxic substances that are deliberately released into our environment to kill organisms which, from the point of view of man, are undesirable. The perfect pesticide would eliminate the target organism and be otherwise harmless. Unfortunately, as Dr Wurster and others have shown, some pesticides become environmental contaminants and have harmful effects that are often distant in time and space from the place where they were applied. These are calculated risks which have to be taken when the pesticide is used; the user believes that the advantages of application outweigh the disadvantages when, or perhaps more particularly if, he himself will not suffer from the side-effects of his actions. My present purpose is to deal with some of the other chemicals which man may introduce into his environment—usually accidentally, but sometimes deliberately, as in the cases of wastes discharged into the air or the sea as a method of disposal— which can also be the cause of environmental degradation.

World opinion has been awakening to a variety of man-made environmental problems during the past few years, and few of these have received more public debate than ‘the pesticide problem’. Strong emotions are evoked in people when they get the idea that they or other animals are being poisoned, regardless of whether the threat is real or imagined. ‘The pesticide problem5 is by no means a single problem, but instead consists of a host of individual and highly diverse problems depending on the pesticide and circumstances involved. In considering the effects of pesticides on nontarget organisms, I propose to organize my remarks into several categories, touching only on those aspects of pesticides that seem more important, and omitting much that in my view appears less critical.

International audience; Female infertility has a multifactorial origin, and exposure to contaminants, including pesticides, with endocrine-disrupting properties is considered to be involved in this reproductive disorder, especially when it occurs during early life. Pesticides are present in various facets of the environment, and consumers are exposed to a combination of multiple pesticide residues through food intake. The consequences of such exposure with respect to female fertility are not well known. Therefore, we aimed to assess the impact of pre- and postnatal dietary exposure to a pesticide mixture on folliculogenesis, a crucial process in female reproduction. Mice were exposed to the acceptable daily intake levels of six pesticides in a mixture (boscalid, captan, chlorpyrifos, thiacloprid, thiophanate and ziram) from foetal development until 8 weeks old. Female offspring presented with decreased body weight at weaning, which was maintained at 8 weeks old. This was accompanied by an abnormal ovarian ultrastructure, a drastic decrease in the number of corpora lutea and progesterone levels and an increase in ovary cell proliferation. In conclusion, this study shows that this pesticide mixture that can be commonly found in fruits in Europe, causing endocrine disruption in female mice with pre- and postnatal exposure by disturbing folliculogenesis, mainly in the luteinisation process.

International audience; Natural plankton communities from a tropical freshwater reservoir (Combani Reservoir, Mayotte Island, Mozambique Channel) were exposed, in 20-l nutrient-enriched microcosms, to two nominal concentrations of three pesticides: the herbicides diuron (2.2 and 11 mu g/l) and paraquat (10 and 40.5 mu g/l) and the insecticide fenitrothion (10 and 100 mu g/l), commonly used in the tropics for agriculture and disease vector control. Bacterioplankton, phytoplankton, and zooplankton communities were monitored for 5 days after exposure, and the concentrations of toxicant and major nutrients were measured. Bacterioplankton growth was noticeable in all systems and was slightly affected by pesticide at any concentration. A transitory increase in thymidine-based bacterial production was observed in diuron- and fenitrothion-treated microcosms, followed by a marked decrease in all microcosms after 5 days. The functional diversity of bacterioplankton, evaluated using BIOLOG ECO (R) microplates, was reduced by exposure to the highest pesticide concentrations. Phytoplankton was affected by pesticides in different ways. Chlorophyll biomass and biovolumes were increased by diuron addition and decreased by paraquat, whereas fenitrothion-treated microcosms remained unaffected relative to controls. Phytoplankton taxonomic diversity was decreased by paraquat and high doses of fenitrothion but was unaffected by addition of diuron. The decrease in diversity was due to a reduction in the number of species, whereas the density of small cells increased, especially after addition of paraquat. Heterotrophic flagellates were sensitive to paraquat and to the highest diuron concentration; a reduction in biomass of up to 90% was observed for 40.5 mu g/l paraquat. Zooplankton, dominated by Thermocyclops decipiens and Diaphanosoma excisum, was slightly sensitive to diuron, and very sensitive to paraquat. High concentrations of the insecticide fenitrothion were effective only on young stages. The potential direct and indirect effects of pesticide contamination on such a simplified plankton food web, typical of newly constructed reservoirs, appear to differ significantly depending on the biological compartment considered. The overall sensitivity of tropical plankton is comparable to the sensitivity for temperate systems, and direct and indirect effects appeared rapidly, within 5 days of exposure.