On Wednesday 11 April 2001, Mr Gérard MIQUEL, Senator, presented the conclusions of a study by the Parliamentary Office for Evaluation of Scientific and Technological Options on the environmental and health effects of heavy metals (mercury, lead and cadmium). This report was a sequel to a debate in the National Assembly on the dangers of mercury in dental amalgam. The rapporteur was supported by a steering committee of scientists. This report had three objectives: to contribute to the public debate, to involve the scientists therein, and to assist decision-making by the political authorities. I. Dental amalgam Two materials are used quite legitimately for treating dental caries: dental amalgam (which contains mercury) and composites. Practically no international scientific studies have found any risks related to the release of the mercury. The Tübingen study, well known to those who oppose the use of amalgam, suffers from too many methodological weaknesses to threaten this virtual unanimity. Notwithstanding this, the complaints and fears of patients must be taken into account. There is no ideal material for treating dental caries. Dental amalgam has therapeutic drawbacks that are too frequently concealed and its use is not always medically justified. Contrary to their training, most dentists do not practice polishing. Finally, any release of mercury, even if it presents no hazard to health, is still a cause of exposure to mercury. Composites evolve too often for their long-term behaviour to be satisfactorily analysed, are unsuitable for all fillings and, above all, depend upon the skill of the practitioner. In any event the replacement of old amalgams by composites is strongly discouraged since it is during application and removal that the risk of mercury release is highest. In medical terms, the amalgam-composite argument is a non-event. On the other hand the disadvantages of dental amalgam to the community are undeniable: a situation involving the presence of 100 tonnes of mercury in French mouths, 10 tonnes of mercury discharged every year and 20 tonnes of mercury sediment in pipes, call for precautions. Such precautions, taking the form of amalgam separators, are either inadequate or ineffective. The question remains as to what should be done with the mercury waste collected. The initial conclusions suggest that a major part is sent for incineration … II. Heavy metals and the environment Heavy metals are already in the environment. All man can do is modify their concentrations and the ways in which they spread. The trend towards reduced use of heavy metals should be encouraged. However two points deserve special attention. Recycling. Recycling is in competition with disposal. The rapporteur, who conducted a study on this topic in 1999, prefers the former solution. Eliminating the use of heavy metals is often extremely expensive, and the outcome uncertain. In the absence of appropriate controls, they are often present in imported products; heavy metal wastes persist in old stocks. Finally, products are replaced by new substances that are not always controlled. The rapporteur is in favour of an active waste management policy encompassing two particular points: controlling traffic in batteries to Spain, and improving the collection and recycling of batteries, cadmium accumulators and fluorescent tubes containing mercury. The spreading of sludge on the land. This issue goes far beyond the single question of heavy metals. The technique of the "slurry spray" and the recurrent food crises demonstrate considerable reticence on the part of farmers. There is no simple conclusion as regards the transfer of heavy metals into plants. The concentrations of cadmium in a given species of wheat vary by factors of 1 to 7 according to variety and 1 to 4 according to the soil. Spreading sludge on land poses a dilemma: either heavy metals migrate into plants and the contamination is a short-term matter, or they remain in the soil in which case the contamination is there for the long term. The continuation of sludge spreading calls for more stringent controls and continued research into transfers. III. Heavy metals and health All of us ingest and inhale heavy metals daily. They are present in nature and their common feature is their toxicity. They are not yet known to have any biological function useful to man. Indeed the less of them one has, the better one’s health. This does not mean that there is any danger in ingesting a single microgramme. It is all a question of dose. Two points deserve special attention. The thresholds. Working out how to calculate thresholds means placing their importance in relative terms since there is considerable uncertainty. Particular care needs to be taken when transposing standards drawn up in one country. When a country does not produce, it obviously wants its imports to contain the least possible amounts of contaminants. If a country does produce, this involves its soil and subsoil meaning that both may contribute doses of contaminants to the products, although without this being hazardous. The French approach is to evaluate risks. In the case of thiomersal for example, a preservative containing mercury, the panic stems from the calculation of mercury in vaccines for babies in the United States. Such a calculation is meaningless here for the simple reason that there is no mercury in baby vaccines in France. The targets to be given special attention. France is in the initial stage of understanding heavy metals, with a wide and reassuring panorama, but attention should now be focused on the populations and sites exposed to risk: estuaries, the region of Provence-Alpes-Côte d’Azur and, primarily, the overseas territories. The unduly high ingestion of the populations of the overseas territories – between +15% and +50% according to the metal concerned – is the result of there being no waste management policy. Actions targeted on a few groups at risk will always be more effective and less costly than the global standards-based approach. Eliminating lead pipes will cost 70 billion French francs for a practically negligible result, while there are much more serious instances of poisoning that also exist. Instead of chaotic actions on a step-by-step basis, sometimes going along with the exposure of problems in the media, the rapporteur calls for priorities to be defined: for example the lead in paint in old buildings, or the poisoning of the public by mercury. The report concludes with a whole series of recommendations including the polishing of amalgam, the replacement of lead shot by non-toxic ammunition for hunting, an audit of the ways in which health checks are carried out on imports, the archiving of soil specimens, and so on.