Lead, drinking water contamination

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

The principal routes of industrial exposure are dermal and inhalation. Occasionally toxic agents may be ingested, if food or drinking water is contaminated. Exposure to the skin often leads to localized effects known as occupation dermatosis caused by either irritating chemicals or allergenic chemicals. Such effects include scaling,... 

It is important to recognize that an NPDWR is not necessarily the same as an MCL, in that protective and adequate regulation of a toxic substance may require technical modalities beyond reductions below an MCL. The amendments implicitly acknowledged this in 1412, allowing the EPA Administrator to regulate lead or other contaminants by means other than an MCL. This part of the Act provided the statutory means for U.S. EPA to regulate drinking water lead via the 1991 Lead and Copper Rule (LCR). 

Hair and bone analyses have revealed that lead contamination of humans in preindustrialized times was apparently higher than today. This might be due to the use in those days of lead pipes for drinking water, lead-containing tinware, and excessive use of lead salts for heavily glazed pottery used as kitchenware. 

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. 

EPA regulations also limit lead in drinking water to 0.015 milligrams per liter (mg/L). The 1988 Lead Contamination Control Act requires the Consumer Product Safety Commission (CPSC), EPA, and the states to recall or repair water coolers containing lead. This law also requires new coolers to be lead-free. In addition, drinking water in schools must be tested for lead, and the sources of lead in this water must be removed. 

Two intermediate-duration studies in rats in which lead was administered mixed in the food as acetate, oxide, sulfide, and lead contaminated soil identified NOAELS of 5 mg lead/kg/day (Dieter et al. 1993) and 6.4 mg lead/kg/day (Freeman et al. 1996) for food intake for all lead forms tested. These doses were the highest doses tested. A 90-day study in rats reported no effects of lead exposure on water intake in rats administered doses of approximately 38 mg lead/kg/day as acetate via drinking water (Kala and Jadhav 1995a). In contrast, rats given a much higher dose of lead acetate in the water (0.6% corresponding to approximately 502 mg lead/kg/day) for 14-50 days showed a 17-20% decrease in water intake (Ronis et al. 1996). 

EPA. 1991d. Maximum contaminant level goals and national primary drinking water regulations for lead and copper. Federal Register 56 26461-26564. 

In the supply of drinking water, it could lead to harmful contaminants being undetected. 

The reaction front reaches the end of the aquifer in the simulation after somewhat less than three pore volumes have been displaced. At this point, the contaminant begins to pass out of the domain. Remediation of the aquifer, however, proceeds slowly, as shown in Figure 32.2. Even after 30 pore volumes have been flushed, some lead remains sorbed to weak sites in the aquifer sediments, and the Pb++ concentration in the groundwater remains above the limits sets as drinking water... 

During elution by clean water, in contrast, a well-defined desorption front fails to develop. Instead, the metal desorbs gradually across a broad area. To clear enough lead from the aquifer to meet drinking water standards, the pore fluid in the simulation must be replaced dozens of times, much more often than was required initially to contaminate the aquifer. 

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