Drinking water, lead concentrations

Fluoride in drinking water appears to be most effective in preventing dental caries if consumed before the eruption of the permanent teeth. The optimum concentration in drinking water supplies is 0.5-1 ppm. Topical application is most effective if done just as the teeth erupt. There is little further benefit to giving fluoride after the permanent teeth are fully formed. Excess fluoride in drinking water leads to mottling of the enamel proportionate to the concentration above 1 ppm. 

Since 1989, as regulatory upper limits for lead in drinking water have fallen, e.g. to 50 pg (EC) and now to 10 pg (WHO), orthophosphate has been added to the water supply in Glasgow to precipitate insoluble lead compounds such as Pb3(P04)2 and Pb5(P04)30H. This has resulted in a fall in the proportion of households with water lead > 10 pg from 49% in 1981 to 17% in 1993. Despite this improvement, an estimated 13% of infants were still exposed via bottle feeds to tap water lead concentrations in excess of 10 pg and it seems very unlikely that further treatment of the water supply will be able to guarantee water lead concentrations <10 pg L . ... 

Lead in water is invisible at the concentrations found in drinking water. Lead-contaminated water does not look dirty or cloudy. 

Moore, M.R., Goldberg, A., Meredith, P.A., Lees, R., Low, R.A. and Pocock, S.J. (1979). The contribution of drinking water lead to maternal blood lead concentrations, Clinica et Chimica Acta, 95, 129-133. 

Moore, M. R., Meredith, P. A., Campbell, B. C., Goldberg, A. and Pocock, S. J. (1977) Contribution of lead in drinking water to blood lead. Lancet, 2, 661-662 Moore, M. R, Campbell, B. C., Meredith, P. A., Beattie, A. D., Goldberg, A. and Campbell, D. (1978) The association between lead concentrations in teeth and domestic water lead concentrations. Clin. Chim. Acta, 87, 77-83... 

Suppose you are asked to develop a way to determine the concentration of lead in drinking water. How would you approach this problem To answer this question it helps to distinguish among four levels of analytical methodology techniques, methods, procedures, and protocols. ... 

The water supply authorities normally insist that (for uses other than drinking-water taps) their main should discharge into a break-pressure vessel, after which the water quality becomes the consumers responsibility. The water tank should be covered against tramp dirt and access by birds, etc., and it must be shielded from sunlight to avoid the growth of algae. Nevertheless, access must be maintained for easy inspection. The distribution pipework is preferably all plastic and lead must be avoided altogether. The use of copper is doubtful with some corrosive waters, and soldered joints in it can lead to unacceptable concentrations of lead in the water. 

G.24 The concentration of toxic chemicals in the environment is often measured in parts per million (ppm) or even parts per billion (ppb). A solution in which the concentration of the solute is. 1 ppb by mass has. 3 g of the solute for every billion grams (1000 t) of the solution. The World Health Organization has set the acceptable standard for lead in drinking water at... 

Mains drinking water is not sterile. Water regulations state that it must contain less than one faecal coliform bacterium per 100 cm3 but concentrations of 103/cm3 of Pseudomonads, one of the main causative organism in industrial product spoilage, are quite common and can lead to infection. 

For each category of land or water body use, one may envision a simplified scenario. In each scenario, only those activities most likely to lead to toxic exposures are considered. For example, In the Industrial scenario, Indoor workers would not be exposed to levels of dust bearing high concentrations of soli contaminants outdoor workers who stir up dry soli with heavy machinery, however, could expect to Inhale contaminant-laden dust. A scenario could Involve more than one exposure pathway. Thus, the Industrial worker might drink water from a contaminated well, In addition to breathing contaminated dust these exposures might represent not only different pathways but different sources. 

The limitations of ELISA methods include the specificity of antibodies, the concentrations of primary antibody and antigen, and the type of reaction solution. Nonspecific binding of either of the antibodies to related antigens, unrelated proteins of other bacteria, or even the microtiter plate may lead to false positive reactions.49,52 57 Use of a monoclonal antibody may decrease crossreactivity with other antigens. For detection of low numbers of bacteria, as in drinking water, the sample may be filtered to concentrate the cells or cultured in a selective broth until it reaches the minimum detection limit for ELISA.49,58 Commercial test kits using dipsticks, immunoblots, and sandwich ELISA methods have been developed for the identification of pathogenic bacteria.58,59... 

Renal Effects. Ingestion of drinking water containing lead was found to be associated with evidence of renal insufficiency in humans (Campbell et al. 1977). Lead concentrations in drinking water were compared to PbB concentrations in 283 residents who ingested this water for a mean of 21.5 years. A highly significant correlation was found for these two parameters. In addition, elevated PbB concentrations were associated with renal insufficiency, reflected as raised serum urea concentrations and hyperuricemia. No renal biopsies were performed. 

Other investigators have been unable to demonstrate lead-induced effects on various components of the immune system in laboratory animals. The effects of lead exposure of varying duration on natural killer cell and T-lymphocytc function were investigated in rats. Male Alderly Park rats received lead as lead acetate in the drinking water at lead concentrations equivalent to 14.3 and 143 mg lead/kg/day for... 

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