It appears that some of these effects, particularly changes in the levels of certain blood enzymes and in aspects of children's neurobehavioral development, may occur at blood lead levels so low as to be essentially without a threshold. Chronic exposure to lead has been linked to cerebrovascular and kidney disease in humans. Lead has the potential to cause cancer from a lifetime exposure at levels above the action level. Usage Patterns Lead is the fifth most important metal in the USA economy in terms of consumption. Three of the six USA lead smelters are from this region, the others are located in Idaho, Montana, and Texas.
Most lead contamination is from corrosion by-products.
Occurrence in Source Water and Distributed Water. From 1987 to 1993, according to the Toxics Release Inventory lead compound releases to land and water totalled nearly 144 million lbs., almost all of which was to land. These releases were primarily from lead and copper smelting industries. The largest releases occurred in Missouri, Arizona and Montana. The largest direct releases to water occurred in Ohio.