Metals in Drinking Water

Prepared by:
Gregory D. Jennings and Ronald E. Sneed
Extension Specialists
Biological & Agricultural Engineering

Mary Beth St. Clair
Extension Specialist
Toxicology

Published by: North Carolina Cooperative Extension Service

Publication Number: AG-473-1

Last Electronic Revision: March 1996 (JWM)

Trace amounts of metals are common in water, and these are normally not harmful to your health. In fact, some metals are essential to sustain life. Calcium, magnesium, potassium, and sodium must be present for normal body functions. Cobalt, copper, iron, manganese, molybdenum, selenium, and zinc are needed at low levels as catalysts for enzyme activities. Drinking water containing high levels of these essential metals, or toxic metals such as aluminum, arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver, may be hazardous to your health.

Metals in your water supply may occur naturally or may be the result of contamination. Naturally occurring metals are dissolved in water when it comes into contact with rock or soil material. Other sources of metal contamination are corrosion of pipes and leakage from waste disposal sites. Metals should be removed from drinking water if they are present at high enough levels to cause concern.

Health Effects

The health effects related to consumption of several metals are presented below. Keep in mind that research is still being conducted on the toxicity of most of these elements. Consult with a physician if your water contains metals and you suspect health problems related to metal consumption.

• Aluminum is the most abundant metal in the earths's crust and therefore is likely to be present at some level in most ground water. The correlation of aluminum consumption to nervous system disorders is currently being researched.
• Arsenic is widespread in the environment due to its natural occurrence and former extensive use in pesticides. Symptoms of chronic arsenic poisoning are weight loss, hair loss, nausea, white lines across the toenails and fingernails, depression, and general fatigue.
• Barium at high doses can cause damage to the heart, blood vessels, and nervous system.
• Cadmium poisoning has been associated with kidney disease, hypertension, and possibly genetic mutation.
• Calcium is necessary for good health. Drinking water containing calcium may provide a significant portion of the required daily intake to prevent such ailments as osteoporosis, hypertension, and cardiovascular disorders.
• Chromium may cause lung tumors when inhaled and has adverse effects on aquatic life.
• Copper in large doses is dangerous to infants and people with certain metabolic disorders. On the other hand, lack of copper intake causes anemia, growth inhibition, and blood circulation problems.
• Iron in water is not a health hazard by itself but it may increase the hazard of pathogenic organisms, since many of these organisms require iron to grow.
• Lead is a cumulative poison, meaning that it remains in the body following exposure. Children under age three are most susceptible to lead poisoning. Minor symptoms include abdominal pains, decreased appetite, constipation, fatigue, and decreased physical fitness. Long-term exposure may cause kidney damage, anemia, nerve and brain damage, and death.
• Magnesium is quickly expelled from the bodies of healthy humans. People with kidney disease, however, may suffer from hypertension, confusion, muscle weakness, and coma.
• Manganese in large doses causes headaches, apathy, irritability, insomnia, and weakness of the legs. Long-term heavy exposure may result in a nervous system disorder.
• Mercury poisoning results in weakness, loss of appetite, insomnia, indigestion, diarrhea, gum inflammation, loosening of the teeth, irritability, memory loss, muscle tremors, and brain damage following large doses.
• Selenium in large doses causes growth inhibition, and may also cause skin discoloration, bad teeth, and some psychological and gastrointestinal problems. A small amount of selenium has been shown to protect against poisoning by such metals as mercury, cadmium, and silver.
• Silver poisoning causes a blue-gray discoloration of the skin, mucous membranes, and eyes, and in high doses it is fatal to humans.
• Sodium at normal intake levels is beneficial to healthy adults. However, people with heart disease or hypertension should reduce sodium intake to lower the blood pressure.

Treatment Options

Methods for removal of some trace amounts of toxic metals include distillation, ion exchange, reverse osmosis, and activated carbon filtration. All systems are expensive to purhase and operate. They are normally installed only on the drinking water line. Your County Extension Office or local water treatment equipment company can provide you with more information on water treatment equipment.

If metals are present in water because of corrosion of pipes, there are several treatment options which are less expensive than those described above. If your water is acid (low pH), the best solution may be to neutralize (raise to pH 7) the water before it enters your home plumbing system. Special filters containing such materials as calcium carbonate (CaCO3), sometimes called calcite, or magnesium oxide (MgO2), sometimes called magnesia, are available for neutralizing acid water. These filters will increase the hardness of your water, and they must be backwashed periodically.

Another neutralization technique involves addition of sodium carbonate (Na2CO3), sometimes called soda ash, into the water system. This should be injected ahead of the pressure tank, and may be mixed with chlorine solution if chlorination is also used. Keep in mind that soda ash adds sodium to your water. To prevent corrosion by creating protective films on plumbing components, chemicals such as polyphosphates and silicates may be injected into the plumbing system. Noncorroding plumbing materials, such as plastic or polyvinyl chloride (pvc) may be used if old pipes must be replaced.

Metal concentrations in tap water are highest after water has rested in the plumbing system for a long time. Before drinking each morning, run your cold water several minutes to flush metals which have accumulated overnight. Elevated temperatures result in increased corrosion. Therefore, hot water heaters should be set only as high as is necessary. To be safe, water from the hot water tap should not be used for drinking or cooking.

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

AG 473-1