Generalities on pesticides in a continental environment
The fact that there is pesticides or remnants of pesticides in water environments of the whole world has been a fact universally acknowledged for years. All water environments are concerned, be it ground water or surface water, including coastal water. The variety of the substances that can be found in the water mirrors the uses of the great groups of substances in agriculture, at home or in industry (mostly weedkillers and also fungicides and insecticides), which sometimes come along with degradation products (aslo called metabolites).
In France, the severity of this contamination is known thanks to the work of the "IFEN" (French Institute for Environment) which regularly publishes a compilation of information provided by various follow-up networks. Those follow-ups tell about the variety of substances and their concentration in the water (more than 400 substances are currently searched in surface water). The information is synthesizes in maps depicting the quality of the rivers according to 5 levels of quality (very good, good, average, tolerable, poor) defined by the "SEQ Eau".
However the variety of the sampling and analysis methods (including the frequency of the samples) makes us cautious in the global interpretation of the results. Nevertheless, the contamination by the phytosanitary products truly exists, its intensity is variable depending on the regions or the areas. Faced with the risks linked to this products and other chemical substances, the Outline Directive on Water, published in 2000, focuses on general objectives aiming at improving the quality of the water, especially for phytosanitary products. We can't estimate the real effects of the presence of phytosanitary products in the water with mere concentration data. According to the various uses of water (making it suitable for drinking, irrigation, recreation or ecological value), the standard threshold values are different and not always detailed molecule by molecule. The threshold values for biological effects are based on the results of toxicity tests (biotests) carried out in laboratories on isolated species (seaweed, daphnidae, fish... [see § 3]) as part of legal procedures for accrediting phytosanitary substances.
Incidentally, we must remind you that before being able to be commercialized, phytosanitary products go trough a very detailed evaluation, which implies an evaluation of the ecotoxicological risks for environment. To be sold in Europe, the actives substances (i.e. the substances which have pesticide features) have to be registered on a positive list, common to all EU countries. The commercial products, which contain one or more active substances as well as other products (additives) aimed at optimizing the action of the active substances are accredited on a national scale, that is to say, they are given an "AMM" (Marketing Authorization). The translation of the results of the toxicity tests into standard values includes security ratios, protective towards environment, which allows to consider the various kinds of uncertainty, linked to the fact that the laboratory tests do not mirror the complexity of the environmental situations. Along with laboratory tests, in situ approaches have been developing these last few years, which allow a better acknowledgment of environmental reality. Biological approaches are interesting for they are including (more than the chemical measure only) and they translate the reality of the facts, but the in situ establishment of causality links between the presence of phytosanitary and the effects are always tricky and sometimes dubious.
(translation: Alice Gautreau)
