Copper in Drinking Water (2000) / Chapter Skim
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6 Risk Characterization
6 Risk Characterization
Pages 127-147
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From page 127... ...
On the other hand, drinking corrosive waters held in copper plumbing can result in copper excess, and the potential for copper toxicity is a concern in that case. This chapter considers copper concentrations in drinking water that might produce copper excess and provides guidance on the establishment of the maximum contaminant level goal (MCLG)
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From page 128... ...
. Large numbers of the elderly appear to have dietary copper intakes below the recommended copper intake.
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From page 130... ...
However, it is recognized that application of the standard regulatory approach for selection of safety factors for essential nutrients can result in levels below essential requirements.
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From page 131... ...
Although additional work is needed to establish the relationship between concentration, volume consumed, and emetic response, the committee considers drinking-water concentration to be an appropriate dose metric for evaluating the MCLG with respect to the acute GI effects of copper. In selecting adjustment uncertainty factors for setting the MCLG, issues to consider are the observations that (1)
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From page 132... ...
COPPER TOXICITY FROM CHRONIC EXPOSURE The primary systemic effect of concern associated with chronic excess copper is liver toxicity (Chapter 5~. In animal models, liver toxicity has been demonstrated in several species and there are case reports of liver disease in humans ingesting excessive concentrations of copper over a long period of time.
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From page 133... ...
These groups should be considered in establishing the MCLG. Carriers of the Wilson-Disease Gene and Other Genetically Sensitive Groups It is likely that a copper sensitivity gene contributes to the hepatic copper toxicity observed in infants and young children ingesting increased amounts of copper in mild and water.
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From page 134... ...
Thus, at least 1% of the population might be susceptible for increased copper retention on the basis of genetic susceptibility. Provided that increased copper retention confers increased risk of liver toxicity, the committee concludes that groups of this size should be taken into account in establishing the MCLG for chronic exposures.
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From page 135... ...
Human case reports and series suggest a range of copper intakes associated with liver toxicity in sensitive individuals. Table 6-3 lists reports in the literature of increased copper exposure in cases of ICT, ICC, and TIC
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From page 136... ...
Those reports are subject to imprecision in exposure ascertainment, but overall suggest that when formulas are made from drinking water containing 3 mg/L and above, genetically sensitive infants might be at increased risk of liver toxicity. It is difficult to ascertain copper concentrations in water and intake associated with toxicity because of varying copper concentrations due in large part to the flushing of the household system as water is used throughout the day.
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From page 138... ...
Nonetheless, it is important to evaluate the potential for liver toxicity from chronic exposure to copper in drinking water when considering changes to the MCLG. CHRONIC COPPER EXPOSURE THROUGH TAP WATER Comprehensive nationwide survey data for copper in drinking water are not available, and therefore estimates of copper intake via water cannot be estimated accurately.
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From page 139... ...
Virtually all fluid of young infants on a powdered formula diet can come from tap water, and the powder formulation is designed to provide the copper requirement. Using information on energy requirements, copper intake via powder formula can be estimated.
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From page 140... ...
WHO (1996) , after considering copper concentrations not associated with detrimental effects in adult humans, set a value of 150 ~g/kg-day as the upper limit of the safe range for mean copper intake for infants.)
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From page 141... ...
Formula-fed infants consuming water contaminated at 6 mg/L would approach doses of 1 mg/kg per day, a dose associated with cases of liver toxicity in genetically sensitive infants by some researchers (Table 63) and approximately a factor of 10 of doses with observed effects in chronic exposure animal studies.
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From page 142... ...
In the case of sensitive populations, a substantial increase in copper intake from water increases the risk for hepatotoxicity. Therefore, in considering changes in the MCLG, the extent to which the copper in water can contribute to the overall dietary copper intake of an individual must be considered.
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From page 143... ...
MCLG - - - - - - 3 mg/L 6 mg/L FIGURE 6~ Total copper intake from water, diet and dietary supplements. Estimates are given for copper concentrations in drinking water at the current MCLG (1.3 mg/L; solid fine)
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From page 144... ...
Given the potential risk for liver toxicity in individuals with polymorphisms, it is recommended that the MCLG for copper should not be increased at this time. Additional information on total copper doses received from drinking water is necessary before the importance of systemic chronic toxicity can be fully evaluated in susceptible populations.
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From page 145... ...
1994. Drinking water maximum contaminant level goals and national primary drinking water regulations for lead and copper.
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From page 146... ...
1988. Copper storage disease of the liver and chronic dietary copper intoxication in two further German infants mimicking Indian childhood cirrhosis.
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From page 147... ...
1996. Wilson's disease and hepatic copper toxicity.
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