Lead-contaminated drinking water also contributes to the overall level of exposure – from as little as 5 percent to more than 50 percent of a child’s total lead exposure. Infants who are fed formula may receive as much as 85 percent of their lead exposure from drinking water. The percentage of exposure to lead attributable to drinking water varies with the levels of lead in the water and with the amount of other lead exposures.
The main cause of lead contamination in drinking water is corrosion of lead-containing materials in household plumbing. In particular, poorly soldered joints where the solder contains lead and a lot of brass fittings may produce high lead levels in the water.
Potential sources of lead in drinking water may include:
· Lead plumbing goosenecks or pigtails;
· Lead service lines and interior household plumbing, especially where lead solder was used;
· Lead-containing alloys, such as faucets or valves made of brass or bronze;
· Private water wells and/or plumbing equipment;
· Water service mains (rarely).
The amount of lead in drinking water attributable to corrosion depends on a number of factors, including:
· The amount and age of lead-containing materials susceptible to corrosion;
· The amount of time the water is in contact with these materials;
· The corrosiveness of the water.
All naturally occurring water contains dissolved gases (oxygen and carbon dioxide) and dissolved solids (silicates, carbonates, sulfates, chlorides, and others) which can attack lead and cause it to corrode. Water’s corrosiveness is determined by the water’s acidity, temperature, and total dissolved solids. Hot, acidic, “soft” (low in dissolved solids) water is the most corrosive towards lead; cold, alkaline, “hard” water is least corrosive.
New solder and brass fittings will release more lead into the water than older ones. However, as time passes, mineral deposits form a coating on the surface of materials in contact with the water that insulates the water from the lead and decreases the rate of corrosion.
Long contact time between the water and the lead-containing materials results in more dissolved lead in the water. Thus, water that remains in the plumbing overnight typically has higher lead levels than flushed water.
In 1986 Congress banned the use of lead-containing materials above specific percentages in public water supply systems and in any plumbing providing drinking water connected to public water systems. Therefore, the level of lead in drinking water should be decreasing.
In order to avoid duplication of effort, Title X does not define lead contamination in water as a lead-based paint hazard. Also, in many cases, it is beyond the control of the owner to effect any corrective measures.
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