[Lead in drinking water, determination of its concentration and effects of new recommendations of the World Health Organization (WHO) on public and private networks management].

In 1993, the World Health Organization (WHO) has given a guideline value of 10 microgram/l for lead in drinking water, a phased approach should lead to a temporary parametric value of 25 micrograms/l within 5 years the final concentration value of 10 micrograms/l being achieved after 15 years. So far the current European Community Directive 80/778 and the French decree 89/3 stipulate a Maximum Admissible Concentration (MAC) for lead of 50 micrograms/l. In a first step we studied the mechanisms of plumbosolvency in corrosive and scaling water. In the first case we have shown that simple oxidative corrosion of lead pipes forms a coating of lead carbonate and hydroxicarbonate on the inside wall of the pipe but "plumbosolvent" waters can dissolve those products, although at a lower level, resulting in a rather high lead concentration. In the case of scaling waters there is a co-precipitation of insoluble calcium carbonate but only on the microcathodics zones of the lead pipe. As this precipitate is poorly cohesive and does not cover the entire surface of the pipe its oxidative corrosion can proceed. In a second step we have shown the major importance of sampling for the determination of lead concentration in drinking water. We therefore compared random day time sampling, first draw and flushed samplings and composite proportional sampling. Only this last method gave a reasonably accurate idea of lead's amounts ingested by drinking water's consumers. The control of corrosion in lead-containing materials involves two successive steps: the reduction of lead concentration to 25 micrograms/l within five years and the compliance with the final 10 micrograms/l concentration 15 years later. The first step consists in water treatments such as pH increase, adjustment of alkalinity and addition of orthophospates. But available data suggest that it is unlikely that lead concentration could be reduced consistently to below 10 micrograms/l by avalable water treatment methods alone but it would enable to match the parametric 25 micrograms/l value in the great majority of cases. Therefore, to unable compliance with the 10 micrograms/l parametric value, it will be necessary to replace all the internal plumbing and supply lead pipes (70,000 buildings for Paris only). Data for materials able to replace lead such as plastic pipes are not yet complete and an currently under investigations. Although the United States Environmental Protection Agency have suggested in its 1988 report on air quality criteria for lead report (EPA 600/8-33-028 aF-dF) that each 1 microgram/l of lead in water can lead to an increase of blood lead levels of approximately 0.2 micrograms/l for a child, the data are still uncertain. The considerable cost of these works (143 billion of french francs for France and 347 billions of french francs for Europe), unrelated to any important Public Health problems, arises an ethical problem which has to be considered in view of many others letal illnesses such as heart and circulatory diseases, cancer and AIDS.