Exposure to lead causes a variety of health effects, and affects children in particular. Water is rarely an important source of lead exposure except where lead pipes, for instance in old buildings, are common. Removal of old pipes is costly but the most effective measure to reduce lead exposure from water.
The disease and how it affects people
Lead is a metal with no known biological benefit to humans. Too much lead can damage various systems of the body including the nervous and reproductive systems and the kidneys, and it can cause high blood pressure and anemia. Lead accumulates in the bones and lead poisoning may be diagnosed from a blue line around the gums. Lead is especially harmful to the developing brains of fetuses and young children and to pregnant women. Lead interferes with the metabolism of calcium and Vitamin D. High blood lead levels in children can cause consequences which may be irreversible including learning disabilities, behavioral problems, and mental retardation. At very high levels, lead can cause convulsions, coma and death.
People are exposed to lead through the air they breathe, through water and through food/ingestion. Toxic effects are usually due to long term exposure. The population groups at greatest risk of exposure are young children and workers. A recent report suggests that even a blood level of 10 micrograms per decilitre can have harmful effects on children's learning and behavior (CDC, 2000). People can be exposed to lead contamination from the motor vehicle exhaust of leaded gasoline, as well as from industrial sources such as smelters and lead manufacturing and recycling industries, from cottage industry uses and waste sites (e.g. contaminated landfills).
Exposure to lead through water is generally low in comparison with exposure through air or food. Lead from natural sources is present in tap water to some extent, but analysis of both surface and ground water suggests that lead concentration is fairly low. The main source of lead in drinking water is (old) lead piping and lead-combining solders. Removing old piping is costly and lead continues to dissolve even from old pipes. The amount of lead that may dissolve in water depends on acidity (pH), temperature, water hardness and standing time of the water. Secondary pollution from industry can contaminate water through the effluents produced.
Other sources include use of lead-containing ceramics for cooking, eating or drinking. In some countries, people are exposed to lead after eating food products from cans that contain lead solder in the seams of the cans. Very small children are especially at risk to exposure, for example through the ingestion of paint chips from lead-based paint.
Scope of the Problem
The major sources of lead vary according to the region and include: industrial use of lead, lead recycling, leaded gasoline and lead piping used in water distribution systems. Lead in the environment is distributed mostly by air but there is some discharge into soil and water. Water is not normally considered the major source of pollution exposure to lead. In individual households with lead piping and soft waters it may be important. As other sources of exposure to lead are increasingly controlled, water attracts increasing attention.
Preventive measures include :
- Environmental standards that remove lead from petrol/gasoline, paint and plumbing.
- If lead pipes cannot be removed, water (cold should be flushed through in the morning before drinking).
- Enforcement of occupational health standards.
- Surveillance of potentially exposed population groups, especially the vulnerable ones (small children, pregnant women, workers).
- Water treatment.
- Removing lead solder from food cans.
- Use of lead-free paint in homes.
- Screening of children for blood levels over acceptable limit and referral for medical care as necessary.
The health based guideline for lead in drinking water is 0.1 milligrams per litre (WHO, 1993). If high levels are detected in a supply, alternative supplies or bottled water maybe necessary to protect young children.
WHO. Guidelines for drinking water quality. 2nd edition. Volume 1: Recommendations. Geneva: WHO, 1993 p49-50
Prepared for World Water Day 2001. Reviewed by staff and experts in the Programme of Chemical Safety (PCS), and Water, Sanitation and Health Unit (WSH), World Health Organization (WHO), Geneva.