LEAD IN DRINKING-WATER, DETERMINATION OF ITS CONCENTRATION AND REPERCUSSION OF THE NEW WHO GUIDELINES ON PUBLIC AND PRIVATE NETWORKS MANAGEMENT

In 1993, the World Health Organization (WHO) has given a guideline val ue of 10 mu g/l for lead in drinking water, a phased approach should l ead to a temporary parametric value of 25 mu g/l within 5 years the fi nal concentration value of 10 mu g/l being achieved after 15 years. So far the current European Community Directive 80/778 and the French de cree 89/3 stipulate a Maximum Admissible Concentration (MAC) for lead of 50 mu g/l. In a first step we studied the mechanisms of plumbosolve ncy in corrosive and scaling water. In the first case we have shown th at simple oxidative corrosion of lead pipes forms a coating of lead ca rbonate and hydroxicarbonate on the inside wall of the pipe but ''plum bosolvent'' waters can dissolve those products, although at lower leve l, resulting in a rather high lead concentration. In the case of scali ng waters there is a co-precipitaiton of insoluble calcium carbonate b ut only on the microcathodics zones of the lead pipe. As this precipit ate is poorly cohesive and does not cover the entire surface of the pi pe its oxidative corrosion can proceed.' In a second step we have show n the major importance of sampling for the determination of lead conce ntration in drinking water. We therefore compared random day time samp ling, first draw and flushed samplings and composite proportional samp ling. Only this last method gave a reasonably accurate idea of lead's amounts ingested by drinking water's consumers. The control of corrosi on in lead-containing materials involves two successive steps : the re duction of lead concentration to 25 mu g/l within five years and the c ompliance with the final 10 mu g/l concentration 15 years later. The f irst step consists in water treatments such as pH increase, adjustemen t of alkalinity and addition of orthophospates. But avalaible data sug gest that it is unlikely that lead concentration could be reduced cons istently to below 10 mu g/l by avalaible water treatment methods alone but it would enable to match the parametric 25 mu g/l value in the gr eat majority of cases. Therefore, to unable compliance with the 10 mu g/l parametric value, it will be necessary to replace all the internal plumbing and supply lead pipes (70 000 buildings for Paris only). Dat a for materials able to replace lead such as plastic pipes are not yet complete and an currently under investigations. Although the United S tates Environmental Protection Agency have suggested in its 1988 repor t on air quality criteria for lead report (EPA 600/8-33-028 aF-dF) tha t each 1 mu g/l of lead in water can lead to an increase of blood lead levels of approximately 0.2 mu g/l for a child, the data are still un certain. The considerable cost of these works (143 billion of french f rancs for France and 347 billions of french francs for Europe), unrela ted to any important Public Health problems, arises an ethical problem which has to be considered in view of many others letal illnesses suc h as heart and circulatory diseases, cancer and AIDS.