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Lead Corrosion

Key Points

  • Lead is a metal that can cause short- and long-term health effects upon exposure to it. Infants and young children are most at risk from exposure.
  • On average, EPA estimates that drinking water contributes to about 10 to 20 percent of lead exposure in young children.
  • The EPA action limit for lead is 15 ppb (parts per billion).
  • An action level is not the same as an MCL. An action level means the concentration of a contaminant which, if exceeded, triggers a treatment or other requirement that a water system must follow.
    If more than 10 percent of tap water samples exceed the action level, water systems must take additional steps to educate the public and reduce the level.
  • Lead solder is a major contributor to lead in drinking water and was used in home plumbing up to 1986. Since the majority of homes in our service area were built after 1986, the amount of lead solder in our service area is low. However, new brass faucets and fittings can also leach lead. In fact, until mineral deposits have a chance to accumulate on interior plumbing, a process which typically takes about five years, new homes could leach small amounts of lead at higher concentrations than older homes.
  • Our analysis of lead in our service area has typically shown levels that are below the action level. In 2005, 90 percent of samples were below the detection level of 2 ppb.
  • To reduce lead in drinking water, consumers can flush their water prior to drinking or cooking. A practical recommendation is to run the water until it gets as cold as it will get. Equally important, use only cold water for drinking or cooking, as hot water is more likely to contain higher contaminant levels for many chemicals including lead.
  • Lead corrosion is caused by high levels of dissolved oxygen, low pH (acidity), and low mineral content (soft water).
  • Water provided to Loudoun Water from the City of Fairfax and Fairfax Water is considered moderately aggressive. Fairfax Water adds a corrosion inhibitor called zinc orthophosphate, to the water, which combines with lead to form several compounds that do not have a strong tendency to dissolve in water.

Lead is a metal which, if it reaches significant levels in the blood, can have short- and long-term effects on people. Infants and young children, including unborn children, are most at risk. Effects of lead exposure on children include delays in normal physical and mental development as well as slight deficits in attention span, hearing and learning abilities. Adults could see a slight increase in blood pressure. Long-term, lifetime exposure could lead to stroke, kidney disease or cancer (EPA 2002b). EPA estimates drinking water contributes about 10 to 20 percent of lead exposure in young children. Other sources include lead paint chips, air, soil, dust and food (EPA 2004a).

The EPA action limit for lead is 15 ppb (parts per billion). That means that if more than ten percent of tap water samples exceed the action level, water systems must take additional steps to educate the public and reduce the level (EPA 2004b). Plumbing installed prior to 1930 is most likely to contain lead. However, lead solder was used in home plumbing up to 1986 (EPA 2002a). New brass faucets and fittings can leach lead. In fact, until mineral deposits build up on the insides of house interior plumbing, a process which typically takes about five years, new homes could leach lead at higher concentrations than older homes (EPA 2004a).

To reduce lead in drinking water, it is important for consumers in new homes or older homes that could contain lead solder or pipe to flush their water prior to drinking or cooking. On different web pages, EPA makes different recommendations as to the length of flushing. A practical recommendation is to run the water until is gets as cold as it will get (EPA 2004c). Equally importantly, use only cold water for drinking or cooking, as hot water is more likely to contain higher contaminant levels for many levels including lead.

Lead corrosion of plumbing pipes and fixtures is caused by high levels of dissolved oxygen, low pH (acidity) and low mineral content (soft water) (EPA 2004a). Water provided to Loudoun Water from the City of Fairfax and Fairfax Water has neutral pH and moderately hard, thereby reducing corrosion potential. Furthermore, Fairfax Water adds a corrosion inhibitor to their water, zinc orthophosphate, which combines with lead to form several compounds that do not have a strong tendency to dissolve in water.

References:

EPA, Actions You Can Take To Reduce Lead In Drinking Water, http://www.epa.gov/safewater/lead/leadfactsheet.html, February 27, 2004a.

EPA, Commonly Asked Questions: Section 1417 of the Safe Drinking Water Act and the NSF Standard, http://epa.gov/safewater/standard/plumbing.html, November 26, 2002a.

EPA, Consumer Factsheet on: LEAD,http://www.epa.gov/safewater/dwh/c-ioc/lead.html, November 26, 2002b.

EPA, Lead in Drinking Water, http://www.epa.gov/safewater/lead/index.html, February 27, 2004c.

EPA, List of Drinking Water Contaminants and MCLs, http://www.epa.gov/safewater/mcl.html#lead1, February 27, 2004b.

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