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Domestic groundwater wells in the eastern and southeastern U.S. at risk of lead contamination

  • Domestic groundwater wells in the eastern and southeastern U.S. at risk of lead contamination

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About one-third of more than 8,300 wells tested across the U.S. had groundwater with chemical characteristics that could cause lead, if present in plumbing, to leach into tap water at levels above the EPA Action Level, according to a new study by the U.S. Geological Survey National Water Quality Program. These characteristics are most common in groundwater in the East and Southeast.

Lead can dissolve into water if the water corrodes a lead-containing material such as lead pipes, lead solder, or brass fittings. The USGS study used measured chemical characteristics of groundwater from more than 8,300 wells tapping groundwater to estimate the potential solubility of lead for each sample. Groundwater with low pH, low alkalinity, and/or low phosphate concentrations had the greatest lead solubility potentials.

Lead can dissolve into water if the water corrodes a lead-containing material such as lead pipes, lead solder, or brass fittings. Groundwater chemistry gives an indication of where that is most likely to happen at high concentrations.

Nationwide, about 33% of untreated groundwater samples had the potential to dissolve 15 micrograms per liter or more of lead, the U.S. Environmental Protection Agency Action Level for lead in treated water from public drinking water supplies, and 5% had the potential to dissolve 300 micrograms per liter or more of lead. The states with the greatest percentage of wells producing untreated groundwater with a high lead solubility potential (300 micrograms per liter or greater) were Maryland, New Jersey, Delaware, Tennessee, and Arkansas. Lead is a toxic metal that can be harmful to human health even at low exposure levels.

In the U.S., groundwater at the wellhead is rarely a source of high lead concentrations in drinking water; rather, the source of the lead typically is somewhere in the plumbing system. Less than 1% of the more than 8,300 untreated groundwater samples evaluated contained dissolved lead at a concentration greater than the U.S. EPA action level of 15 micrograms per liter.

Potentially corrosive groundwater can be treated to minimize the leaching of lead into drinking water, and such treatment is required for public-water supplies to prevent corrosion of lead-bearing materials if the water at customer taps contains lead. However, lead testing and corrosion treatment for domestic wells are not required by federal law or by most states. Households that drink self-supplied (domestic well) water therefore can be at greater risk of consuming water that contains lead than households that rely on public-water supplies.

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