The facts on copper
What is Copper?
Copper is a light reddish-brown metallic element with the symbol Cu and atomic number 29 on the periodic table of the elements. The name copper is derived from the word Cyprus, the island where the Romans obtained their copper supply. It was the first metal to be widely used by humans.
Naturally occurring pure copper is called native copper. Copper is also found in nature mixed with other elements in a number of compounds, many distinguished by their blue-green color. Turquoise, malachite, and azurite are three brilliantly colored copper compounds used as gemstones. Copper sulfate and copper oxide are two important copper compounds used in industry and agriculture. Copper can be mixed with other metals to form alloys, such as bronze (copper and tin) and brass (copper and zinc).
Oxidized copper, or copper that has been exposed to air, develops a green coating or patina that can be seen on old copper pennies, the Statue of Liberty, and copper roofs.
Where is Copper Found?
Copper is naturally present in rock, either in its pure form or in compounds. Geological, meteorological, and biological processes disperse copper into the air, soil, and water as well as into organisms.
The largest known copper ore deposits in the world are in Chuquicamata in the Chilean Andes, and the largest deposit of native copper is in Michigan's Upper Peninsula. The major producers of copper are Chile, which supplies 35 percent of world's copper and the United States, which produces roughly 11 percent. Canada, the countries of the former Soviet Union, Zambia, China, Poland and the Democratic Republic of the Congo are also copper-producing nations.
Human activity accounts for much of the copper found today in air, soil, and water. Industrial operations such as smelters, foundries, power stations, incinerators and other combustion sources emit copper into the atmosphere, where it can return to the earth in precipitation. Smelters and other copper production facilities emit high copper concentrations to surrounding air and soil. Copper mines can be a significant source of pollution. Copper and other minerals present in the tailings the waste left over after ore has been extracted from rock make their way into soil and waterways. Water can be polluted by a number of other copper sources as well, including agricultural runoff from farms using copper-based pesticides.
Copper is an essential element for all living organisms, therefore it is present in he food we eat whether plant or animal and in human tissue.
What are the Uses of Copper?
Humans have been using copper for nearly ten thousand years. Since ancient times, copper has been used by itself and in combination with other metals to make weapons, tools, household items, and artwork.
Copper's high conductivity made it the metal of choice in the development of electrical engineering in the 18th and 19th centuries. Copper is the third most widely consumed metal globally after steel and aluminum. Today, construction accounts for the largest consumption of copper. Copper is used in construction of homes and other buildings, the manufacture of cars and airplanes, and for plumbing pipes. The electric and electrical products industry is the next largest consumer of copper. Copper is also used in telecommunications. A significant amount of copper used in the United States comes from recycled scrap and scrap left over from copper production.
A 1936 U.S. copper alloy penny, a 1943 zinc-plated steel penny, and a modern 2004 copper-coated zinc penny. Photo credit: Dartmouth Toxic Metals Research Program
United States pennies were made of pure copper from 1793 to 1837. In subsequent years, they were made of various copper alloys, including bronze and brass. In 1943, when copper supplies were directed to the war effort of World War Two, the majority of pennies minted were zinc-plated steel. Since 1982, pennies contain only 2.5 percent copper they are zinc with a thin copper coating.
Copper sulfate, a naturally occurring and manufactured copper salt, is used as a fungicide on crops, as a pesticide to kill snails and slugs, and as water treatment to kill aquatic vegetation. This chemical has serious chronic toxicity with implications for agricultural workers and the environment.
Modern copper or copper alloy bangles from Zimbabwe. Photo credit: Dartmouth Toxic Metals Research Program
Copper compounds are also used to preserve wood and as leather tanning chemicals and mordant (fixative) in textile dyeing. Copper is still used today for artwork and jewelry around the world. In parts of Africa, copper bangles and artwork are made from discarded copper wire and scraps. In many parts of South and Southeast Asia, copper, brass, and bronze are widely used in cookware, dishes, religious statues and artwork. Navajo and other southwestern U.S. tribal nations sometimes use copper in jewelry.
Do we need Copper for Health?
Foods that contain copper. Photo credit: Dartmouth Toxic Metals Research Program
Copper is an essential nutrient for all living things. Copper is a component of more than 30 enzymes in the human body, including some involved in collagen synthesis. In humans copper is necessary for the healthy development of connective tissue, nerve coverings, and bone. It is also involved in both iron and energy metabolism. Copper deficiency, although rare, can cause anemia and connective tissue, bone, and nervous system abnormalities.
The Dietary Reference Intake (DRI) guidelines, set in 2001 by the U.S. Food and Nutrition Board of the National Academies Institute of Medicine, set both the recommended dietary allowances (RDA) and the upper intake levels for copper. The group's intake recommendation is 0.9 milligram of copper a day for adults, more for lactating women (1.3 milligrams) and less for children (0.34 milligrams for children up to three and 0.44 milligrams for children between four and eight years). The upper limit is 10 milligrams per day for healthy adults. Since the body does not synthesize copper, this essential level of copper must come from nutrition.
Good sources of dietary copper are liver and other organ meats, oysters, nuts, seeds, dark chocolate, and whole grains. Some copper is also present in potatoes, raisins, mushrooms, and chickpeas and other legumes. Drinking water supplied in copper pipes can contribute to copper intake.
Excessive dietary zinc can cause copper deficiency.
Can Copper Pose a Health Risk?
Just as some copper is essential for good health, too much can be harmful. A healthy human can excrete some excess copper. However, high doses, long-term exposure, and certain routes of exposure can overwhelm the biological processes that excrete excess copper from the body.
Inhalation of copper dust and fumes (from copper producing and processing facilities) can affect the respiratory tract causing coughing, sneezing, and pain in the chest. It also can adversely affect the gastrointestinal tract causing nausea and diarrhea. Liver and endocrine function may also be affected. Some studies have shown changes in blood including decreased hemoglobin and erythrocyte count after exposure to copper by inhalation. Copper dust and fumes can cause eye irritation, headaches and muscle aches.
Ingesting large amounts of copper compounds (such as copper sulfate) can cause death by nervous system, liver and kidney failure. Some studies have shown that ingesting copper may also be implicated in coronary heart disease and high blood pressure although other studies have shown that copper deficiency may play a role in coronary heart disease. High levels of copper in drinking water can cause vomiting, abdominal pain, nausea, diarrhea and has been reported in people drinking water from copper pipes.
Zinc and chelating agents can be used to remove excess copper from the body.
Copper is not known to play a role in cancer or birth defects.
Who is at Risk of Harm from Copper Poisoning?
Large doses of copper-containing compounds, such as copper sulfate, are poisonous even to those with a healthy liver. However, some people are at greater risk of copper toxicity. People with certain liver diseases and those with an inherited inability to metabolize copper are particularly sensitive to copper toxicity, such as people with Menkes disease, hereditary aceruloplasminemia, and Wilson's disease.
Penicillamine, whose chemical structure is shown here, is used as a chelating agent in the treatment of Wilson's disease. Photo credit: Dartmouth Toxic Metals Research Program
People with Wilson's disease, a recessive hereditary inability to eliminate copper from the body, are particular risk of developing toxic levels of copper in their tissues, particularly the liver and brain. Untreated, this condition can lead to liver failure, severe neurological or psychiatric problems and death.
Wilson's disease can be effectively treated using zinc acetate, which blocks the absorption of copper. Chelating agents are also effective by binding to copper in the body and allowing it to be excreted in the urine. Both types of treatment must be continual throughout the life of the patient. Reducing dietary copper can also reduce the symptoms, although this alone is not effective treatment. Carriers of the disease people with one copy of the defective gene will not develop the disease but may have slightly abnormal copper metabolism. Although Wilson's disease is found in only one out of 30,000 people worldwide, as much as one in 100 people may carry the gene for the disease. There are several methods for diagnosis of the disease, such as urine analysis and liver biopsy. There is no genetic screen available yet to identify individuals who are at risk because the disease is caused by any one of 200 mutations.
There are other conditions involving copper toxicity that appear to have a genetic link. Indian childhood cirrhosis, which affects children in South Asian countries, appears to be a result of a genetic predisposition toward copper sensitivity combined with a high exposure to copper (often from milk boiled in copper or brass pans). Similar conditions in children have appeared in other parts of the world where water contained high levels of copper. Again, these children appear to have a genetic predisposition toward poor copper metabolism.
People who live near or work in copper-producing facilities such as mines, smelters or refining facilities, or in copper manufacturing at elevated risk for exposure to excessive amounts of copper. Exposure can occur through inhalation of copper dust and copper fumes.
Is Copper in the Environment a Health Risk?
The answer to this question is complex. Copper is a necessary nutrient and is naturally occurring in the environment in rocks, soil, air, and water. We come into contact with copper from these sources every day but the quantity is usually tiny. Some of that copper, particularly in water, may be absorbed and used by the body. But much of the copper we come into contact with is tightly bound to other compounds rendering it neither useful nor toxic. It is important to remember that the toxicity of a substance is based on how much an organism is exposed to and the duration and route of exposure.
There are sources of copper in the environment that do pose a health risk. Roughly half of the hazardous wastes sites on the EPA's National Priorities List are known to contain copper. Air and soil near copper processing facilities such as smelters typically have much high levels of copper than that in other areas. Agricultural runoff can contain copper-based pesticides. These can pose a health risk to humans. However, copper binds very easily to compounds in soil and water, reducing its bioavailability to humans.
A potential source of excessive copper exposure in humans is from drinking water transferred through copper pipes and brass sink fixtures. Small amounts of copper from plumbing leach into water, particularly hot water and water that has been sitting in the pipes for several hours or overnight. Acidic (low pH) water will leach more copper than more basic (high pH) water will. Soft water is likely to contain more copper than hard water because it doesn't contain the minerals that build up a protective layer on the interior of pipes, preventing copper from leaching. Blue-green water stains below faucets are an indicator of copper in the water. Some people who drink water with high copper levels may experience nausea, vomiting, abdominal pain, and diarrhea. The amount of copper that is typically found in water from copper plumbing is usually not a health threat.
Using only water from the cold tap for drinking and preparing food can reduce the amount of copper that leaches from plumbing. Running the water until it gets very cold after it has been sitting the pipes overnight or for more than six hours will reduce the copper levels as well. Making sure that no electrical appliances are grounded to the plumbing can reduce corrosion of the pipes. Water filters can also remove copper from water. Check the filter manufacturer's label to see if copper is one of the chemicals filtered out.
Are There Federal Guidelines or Standards on Copper?
Under the federal Safe Drinking Water Act, the U.S. Environmental Protection Agency (EPA) limits the amount of copper in public drinking water supplies to 1.3 mg per liter. Under the Superfund Act, the EPA considers 5,000 pounds of copper or 10 pounds of cupric sulfate in an area to be a hazardous substance.
The U.S. Food and Drug Administration (FDA) allows no more than 1 mg copper per liter of bottled water. The National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) each have their own standards for the amount of copper and copper fumes allowable in the workplace. To read about their specific regulations, refer to the following website: http://www.osha.gov/SLTC/metalsheavy/copper.html.
Where Can I Learn More About Copper?
The Agency for Toxic Substances and Disease Registry (ATSDR) of the U.S. Centers for Disease Control and Prevention has an excellent web-based public health statement on copper, available at: Agency for Toxic Substance & Disease Registry.