Drinking water effects

Screening smokes, by their intended use, are deliberately released into the environment, albeit in localized and very small amounts. Thus, the possibility for environmental problems, including ecotoxicological issues, needs consideration. Particular aspects that may need to be taken into account include local decontamination, phytotoxicity, effects on domestic and wild animals, avian and aquatic toxicity, contamination of food and drinking water, effects on plant sewage organisms. 

Dietary Magnesium and Drinking Water Effects on Human Health Status... 

The primary non-carcinogenic toxic effect of uranium is on the kidneys. Published studies in rats, rabbits, and humans show effects of chronic uranium exposure at low levels in drinking water. Effects seen in rats, at the lowest average dose of 0.06mgUkg day including histopatho-logical lesions of the kidney tubules, glomeruli and interstitium are considered clearly adverse effects albeit not severe (OEHHA, 2001). 

Rats showed no adverse effects from 5.0% dipropylene glycol in their drinking water for 77 days, but at a dose of 10.0% in the drinking water, kidney and Hver injury and some deaths occurred (35). A sufficient number of studies have not been carried out on tripropylene glycol to permit conclusions to be drawn regarding its chronic oral toxicity. 

Avitrol [504-24-5] (4-anHnopyridine) (24), mp 155—158°C, bp 273°C, has repeUent—toxicant properties for birds and is classed as a severe poison and irritant. This secondary bird repeUent can be used as a broadcast bait, causing uncoordinated flight and distress caUs and escape responses in nearby birds (57). A reevaluation shows lack of effectiveness of 1% baits but better control of blackbirds with 3% baits (58). Suspected contamination of drinking water with 4-aminopyridine has been reported in toxicosis of Brahman catde and horses (59). 

In 1980, the EPA pubHshed ambient water quaHty criteria for silver. An upper limit of 50 f-lg/L in natural waters was set to provide adequate protection against adverse health effects (38). In 1992, EPA deleted the human health criteria for silver from the ambient water quaHty criteria to be consistent with the drinking water standards (39). 

Administration of 5 ppm barium, the acetate, to mice in the drinking water in a life-time study had no observable effects on longevity, mortality, and body weights, or on the incidence of tumors (53). Long-term studies in rats exposed to Ba " in drinking water containing 5 mg/L, as acetate, or 10—250 mg/L, as chloride, resulted in no measurable toxic effects (47). 

Other Uses. As a biocide, chlorine dioxide is more effective than chlorine over a wider pH range. Chlorine dioxide is also less corrosive and more compatible with some materials of constmction. Chlorine dioxide has a wide variety of small appHcations in drinking water, food processing (qv), cooling towers, and oil recovery. In these areas, chlorite is the preferred source of chlorine dioxide. 

Sodium chlorite is not Hsted by the USEPA or any regulatory authority as a carcinogen. Studies conducted ia mice and rats did not show an increase in tumors in animals exposed to sodium chlorite in thek drinking water. Sodium chlorite has been found to have mutagenic activity in some in vitro test systems such as the Ames Salmonella reverse mutation assay without the presence of metaboHc activators. The significance of these test results in regard to human health is not clear because of the oxidizing effects of the chlorite ion (149). 

Fluorides. Most woddwide reductions in dental decay can be ascribed to fluoride incorporation into drinking water, dentifrices, and mouth rinses. Numerous mechanisms have been described by which fluoride exerts a beneficial effect. Fluoride either reacts with tooth enamel to reduce its susceptibihty to dissolution in bacterial acids or interferes with the production of acid by bacterial within dental plaque. The multiple modes of action with fluoride may account for its remarkable effectiveness at concentrations far below those necessary with most therapeutic materials. Fluoride release from restorative dental materials foUow the same basic pattern. Fluoride is released in an initial short burst after placement of the material, and decreases rapidly to a low level of constant release. The constant low level release has been postulated to provide tooth protection by incorporation into tooth mineral. 

Chlorine Dioxide. Like ozone, chlorine dioxide [10049-04-4] is a powerflil oxidant. It is usually generated as used. It has been used for disinfecting drinking water and bleaching paper pulp. Its effectiveness in killing microorganisms is well documented (305,306), and it has received recent study as a gas to sterilize medical devices. It requites 50% rh or higher to be effective. Bacterial cells had a D-value of 2.6 min and spores of 24 min (307). 

Seawater Distillation. The principal thermal processes used to recover drinking water from seawater include multistage flash distillation, multi-effect distillation, and vapor compression distillation. In these processes, seawater is heated, and the relatively pure distillate is collected. Scale deposits, usually calcium carbonate, magnesium hydroxide, or calcium sulfate, lessen efficiency of these units. Dispersants such as poly(maleic acid) (39,40) inhibit scale formation, or at least modify it to form an easily removed powder, thus maintaining cleaner, more efficient heat-transfer surfaces. 

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