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