Lead: From Water Technology Magazine Volume 31, Issue 8 - August 2008

Chemical symbol: Pb

Atomic number: 82

What it is:

• Lead is a toxic metallic element that was regularly used in industrial capacities for most of the 20th century.


• Lead constitutes only 0.00013 percent of the Earth’s crust, but easy mining and refinement keep it from being considered rare.


• Lead is usually found in these ores/compounds:


• Lead sulfide (galena): PbS


• Lead sulfate (anglesite): PbSO4


• Lead carbonate (cerussite): PbCO3

Where found:

• Lead rarely occurs naturally in water. Source waters that contain lead have usually been affected by industrial, smelting or mining wastes.


• Lead can enter water by leaching from pipes by way of corrosion, a reaction of water with metal caused by low pH, low mineral content in water, and dissolved O2.


• Plumbing installed before 1930 is most likely to contain lead.


• Lead can also leach from copper and brass.

Health effects:
The risk of lead poisoning is highest in children and pregnant women. Children absorb 30-75 percent of the lead they ingest; adults absorb only 11 percent. Effects of lead poisoning include:

• Damage to the brain, kidneys and red blood cells


• Coma and convulsions


• High blood pressure


• Slowed physical growth, hearing problems and reduced intelligence in children.

Regulation:

• US Environmental Protection Agency (EPA) maximum contaminant level (MCL) in drinking water for lead is 15 parts per billion.


• US EPA MCL goal: zero


• Amendments to the Safe Drinking Water Act in 1986 set the maximum allowable lead limit at 0.2 percent for solder and flux and at 8.0 percent for pipes.

Water treatment:

• Removal of lead source


• Corrosion control methods in pipes, including: pH and alkalinity adjustment; calcium adjustment; silica or phosphate-based corrosion inhibition


• Ion exchange softeners operated at no more than 2.0 to 3.0 gallons per minute flow rate per cubic foot


• Reverse osmosis removes 90-95 percent of the soluble lead impurities and also acts as a barrier to lead.

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Sources: Water Quality Association, US EPA, NYS Department of Health, American Water Works Association, Minnesota Department of Health, industry sources.