What Is Arsenic?

Arsenic is a naturally occurring element in the environment. It has no taste or smell. Although sometimes found in its pure form as a metal, arsenic is usually a part of chemical compounds. These compounds are usually divided into 2 general categories:

• inorganic compounds (combined with oxygen, iron, chlorine, and sulfur) 
• organic compounds (combined with carbon and other atoms)

Arsenic-contaminated inorganic compounds are found in industry, in building products (arsenic-treated wood), and in arsenic-contaminated water. This is the form of arsenic that tends to be more toxic and has been linked to cancer.

Organic arsenic compounds in fish and shellfish may account for significant dietary intake of arsenic. These compounds are much less toxic than the inorganic arsenic compounds. Organic forms of arsenic have not been linked to cancer.

Lead and copper ores are also commonly contaminated with small amounts of arsenic.

How is Arsenic Used?

Although arsenic is known to be a poison, arsenic compounds have many uses, such as:

• in wood preservatives (currently the major use) 
• in insecticides and herbicides (although its use in U.S. agriculture ended in 1993) 
• as a preservative in animal hides 
• as an additive to lead and copper for hardening 
• in glass manufacturing to take away the natural green color 
• in some medicines (mostly for veterinary use) 
• as arsine gas to enhance electrical junctions in semiconductors

In the 1800s and early 1900s, inorganic arsenic was commonly used as rat poison and in treating some human diseases, such as syphilis. A widely used arsenic compound, Fowler’s solution (potassium arsenite), was prescribed for chronic infections, anemia, and skin diseases. Pentavalent arsenic is still used to treat advanced trypanosomiasis (a disease caused by parasites, which is rare in the United States but more common in Africa), and arsenic trioxide is being used today as a treatment for promyelocytic leukemia.

How Are People Exposed to Arsenic?

People may be exposed to arsenic in many ways. Very high doses have been used in murder or suicide attempts (see table below). Some jobs may lead to high exposures over long periods of time when workers breathe in or swallow dust that contains arsenic compounds. But such exposures are now rare in the United States. People who live near current or former industrial or agricultural sources of arsenic may have fairly high exposures from inhaling fumes or eating contaminated food. People who live in areas where arsenic is naturally high in drinking water may take in high levels of arsenic over the course of a lifetime. Finally, low chronic exposures may occur through diet, especially among people who eat a lot of seafood.

Exposure at Work

Arsenic has not been produced in the United States since 1985. In the past, workers in smelters and in plants that made, packaged, or distributed pesticides that contained arsenic had high exposures from breathing in arsenic fumes and dust. Today workplace exposure to arsenic may still occur in the wood preservative industry. Workers in semiconductor manufacturing may be exposed to arsine gas. Regulations are in place to limit workplace exposure.

Exposure in the Community

Community exposure to arsenic may occur near previous or current industrial sources. Facilities such as wood preservative and glass factories may contaminate nearby air and soil. Communities near former smelters, or near fields or orchards where arsenic pesticides were used, may also have contaminated soil.

Drinking Water

Drinking water is an important and potentially controllable source of arsenic exposure. In fact, drinking water accounts for most human arsenic exposures worldwide. In parts of Taiwan and Japan, in the Ganges River delta (especially in Bangladesh), and in parts of western South America (in northern Chile, southwestern Bolivia, southern Peru, and Argentina), arsenic occurs naturally in drinking water at levels from several hundred to several thousand parts per billion (ppb).

Water in some areas of the United States, especially in the West, also contains arsenic, with the highest areas in the 50 to 100 ppb range. Most U.S. areas with high levels of arsenic in drinking water are rural communities. Albuquerque, New Mexico, is the only urban area in the U.S. with substantial arsenic concentrations in drinking water. Arsenic levels in public drinking water are regulated. As of January 2006 the maximum contaminant level for inorganic arsenic permitted in U.S. drinking water is 10μg/L (micrograms per liter) or 10 ppb.

Playground Equipment

Chromated copper arsenate (CCA) is a chemical preservative that protects wood from rotting. It has been used to pressure treat lumber used for decks, playgrounds (playsets), and other outdoor uses since the 1930s. In fact, starting in the 1970s, the majority of the wood used in residential settings was CCA-treated wood. In 2003 the EPA and CCA makers agreed to end the manufacture of CCA-treated wood for most consumer applications. However, this wood can still be found on playgrounds and there is no way to look at it and know whether or not it is CCA treated. If you are not sure if a playset is composed of CCA-treated wood, you should assume that it is.

An individual child’s risk from arsenic in CCA-treated playground equipment will vary depending on many factors, including the amount of arsenic released from the CCA-treated wood, the amount of arsenic picked up on the hands, the number of days and years the child plays on the wood, and the amount of arsenic transferred to the mouth by hand-to-mouth activity. Hand-to-mouth behavior is the primary source of exposure to arsenic from CCA-treated playground equipment. To reduce this, parents and caregivers should thoroughly wash children’s hands with soap and water immediately after playing on all pressure-treated wood playground equipment. It has also been suggested that children not eat while on wooden playground equipment.

Calling the playset manufacturer might help you find out if the playset contains CCA-treated wood. If you decide to remove your CCA-treated wood playset, the EPA states that CCA-treated wood should never be burned in open fires, stoves, fireplaces, or residential boilers. Contact the EPA (http://www.epa.gov/) or your state or local solid waste management offices to get instructions on how to safely dispose of CCA-treated wood.

Other Possible Sources of Arsenic

Other potential exposures to arsenic are generally at lower levels and for shorter periods of time than those from past occupational exposures or from highly contaminated drinking water. Because arsenic is commonly used in wood preservatives, people can be exposed by breathing sawdust from cutting arsenic-preserved wood or breathing the smoke from burning this wood. Hazardous waste sites can be another source of arsenic exposure. Burning cigarette tobacco and fossil fuels (such as coal) also releases arsenic into the air.

Arsenic in Food

Finally, a low level of arsenic exposure is common in the diet. In fact, most meat and vegetables contain low levels of arsenic. The average U.S. diet contains about 50µmg (micrograms) of arsenic (mostly organic) per day. Diets high in seafood can contain several times that amount of mostly the less dangerous organic forms of arsenic.

Does Arsenic Cause Cancer?

The study of the carcinogenicity (cancer-causing potential) of arsenic is unusual because most evidence comes from human studies. The first evidence linking arsenic with cancer came from case reports of skin cancer after exposure to inorganic arsenic in medical treatments, drinking water, or pesticides. Studies were then done to look at the connection between arsenic and cancer. These studies fell into 2 broad categories:

• studies of lung cancer in highly exposed workers 
• studies of lung, skin, and urinary tract cancers in communities with contaminated water

Breathing Arsenic-Contaminated Dust

Many studies have looked at cancer occurrence among workers who manufactured pesticides containing arsenic and those who worked in mines and copper smelters. Their inhaled exposures were often very high -- the air concentrations of arsenic in smelters before the 1970s were commonly 50 to 100 times higher than the current occupational limit of 0.01mg/m3. Studies in the United States, Sweden, and Japan have given researchers solid evidence after following several thousand workers for as long as 40 or 50 years. Together, these studies consistently have shown up to a 10-fold increase in lung cancer risk with higher and more prolonged exposures. Other cancers have not been consistently linked to inhaled arsenic exposure.

Drinking Arsenic-Contaminated Water

Worldwide

Studies of populations with high levels of arsenic in drinking water in West Bengal, Taiwan, Bangladesh, China, and Argentina have shown elevated risks of cancers of the urinary tract, lung, skin, and, less consistently, cancers of the colon and liver.

Some of these studies reported an increased risk of transitional cell bladder cancer at levels of arsenic below the then current U.S. standard of 50 ppb (parts per billion). For example, a 2001 study from Taiwan compared the incidence of this cancer in communities with known levels of arsenic in their drinking water. The findings showed that the bladder cancer risk for residents of communities with levels above 100 ppb was over 15 times that of people living in areas with levels no higher than 10 ppb.

A series of studies in Córdoba, Argentina, divided that state’s 26 counties into 3 categories: high exposure, medium exposure, and low exposure. In the high-exposure area, elevated arsenic levels in drinking water averaged 178 ppb. The higher the level of arsenic people were exposed to, the more likely they were to develop bladder cancer, lung cancer, and kidney cancer.

In the United States

Another study looked at a population in Utah exposed to arsenic concentrations in drinking water that ranged as high as 166 ppb. There was no increase in cancers of the urinary tract, lung, or skin, as might have been expected. The only significant increase was of prostate cancer in men. This cancer had not previously been connected with arsenic in drinking water and the significance of this finding is unclear. However, this was a relatively small study in which fewer than 600 people were classified as highly exposed, so the ability to detect increases in cancer risk was limited. Also, this was a unique population of Mormons with little or no exposure to alcohol, tobacco, and caffeine, so the relevance of these results to other groups with less healthy lifestyles may be limited.

For most Americans who are on piped or public water systems, drinking water is not a major source of arsenic. Even in those areas of the United States where exposure in well water is above the EPA's guideline of 10 µg/L, studies to date have not found a significant link between arsenic exposure and cancer.

What Do Animal and Laboratory Studies Suggest?

Arsenic has not been found to cause cancer in laboratory studies. In fact, arsenic is highly unusual in this respect -- it causes cancer in humans but not in laboratory animals. However, arsenic compounds have been found to damage the DNA of animal cells grown in laboratory dishes. DNA damage was also seen in the white blood cells of smelter workers exposed to arsenic and in patients treated with arsenic-containing compounds.

What Do the Experts Say?

The National Toxicology Program (NTP) evaluates exposures that are thought to cause cancer. These exposures are included in the Reports on Carcinogens, which is published every 2 years. Each exposure is assigned to 1 of 2 categories: "known to be human carcinogens," or "reasonably anticipated to be human carcinogens." The first category includes substances for which human studies provide "sufficient evidence" of causing cancer (carcinogenicity) in humans. The second category includes substances for which there is limited evidence of carcinogenicity in humans and/or sufficient evidence of carcinogenicity in experimental animals. Using this system, the NTP classifies arsenic compounds as a known human carcinogen.

The International Agency for Research on Cancer (IARC) also evaluates exposures that may be carcinogenic. IARC classifies exposures into 1 of 4 categories:

• Group 1 exposures are those "known to be carcinogenic to humans," usually based on "sufficient" human evidence, but sometimes based on "sufficient" evidence in experimental animals and "strong" human evidence. 
• Group 2 exposures are divided into 2 categories. Group 2A ("probably carcinogenic to humans") has stronger evidence, and Group 2B ("possibly carcinogenic to humans") has weaker evidence. 
• Group 3 exposures are not considered classifiable because available evidence is limited or inadequate. 
• Group 4 exposures are "probably not carcinogenic to humans," based on evidence suggesting lack of carcinogenicity in humans and in experimental animals.

The IARC rates arsenic and arsenic compounds as carcinogenic to humans (Group 1). IARC notes that this evaluation applies to the group of chemicals as a whole and not necessarily to all the individual chemicals in the group.

The Environmental Protection Agency (EPA), through its Integrated Risk Information System, uses a classification system very similar to that of IARC. It classifies exposures into 5 different groups:

• (Group A) human carcinogen 
• (Group B) probable human carcinogen 
• (Group C) possible human carcinogen 
• (Group D) not classifiable as to human carcinogenicity 
• (Group E) evidence of non-carcinogenicity for humans

The EPA classifies arsenic as a human carcinogen (Group A).

Does Arsenic Cause Any Other Health Problems?

Arsenic is an acute (short-term) and a chronic (long-term) toxin.

Acute Exposure

An acute exposure by breathing in arsenic may cause a sore throat and irritated lungs. Acute exposure by either breathing or swallowing arsenic can also damage nerves, the digestive system, and the skin.

Acute exposure to arsenic-laced well water (typically containing more than 1,200 micrograms per liter [μg/L]) is known to cause things like

• abdominal pain 
• vomiting 
• diarrhea 
• muscular weakness and cramping 
• arm and leg pain 
• skin changes or rashes 
• swelling of the eyelids, feet, and hands

An acute exposure to large amounts of arsenic can be fatal.

Chronic Exposure

Chronic exposure to lower levels of arsenic is called arsenicosis. It can also cause health problems, besides cancer, including

• headache 
• confusion 
• blood vessel disease (atherosclerosis) 
• nerve damage leading to numbness and weakness (called peripheral neuropathy) 
• worsening of the complications of diabetes 
• high blood pressure (hypertension) 
• irregular heartbeats 
• liver and kidney damage 
• a shortage of red and white blood cells

Skin changes are a common outward sign of chronic arsenic exposure. The changes include a darkening of the skin and the appearance of keratoses (pre-cancerous skin growths), usually on the palms and soles.

Some evidence shows that arsenic is associated with ischemic heart disease. Finally, evidence also suggests that arsenic may interfere with the function of some hormones.

What Should I Do If I Think I’ve Been Exposed to Arsenic?

Several laboratory tests are used to assess arsenic exposure. Tests of hair and fingernails can detect relatively high-level arsenic exposures during the previous 6 to 12 months, but these tests are hard to standardize. Blood tests for arsenic show only very recent exposures because arsenic is cleared from blood within a few hours. Because of this blood tests are not useful when looking for long-term exposure. Urine tests are the most reliable method for identifying low levels of arsenic exposure, but these too reflect recent exposures because most absorbed arsenic is excreted in urine within days. Doctors and patients should also be aware that a large part of the arsenic found in urine may be organic arsenic (the less dangerous form of arsenic) that comes from eating fish.

Because arsenic exposure increases the risk of skin, bladder, kidney, and lung cancer, people who have been exposed should learn about other risk factors and prevention strategies for these cancers. Avoiding risk factors such as tobacco use and excessive sun exposure is especially important if you have been exposed to arsenic. You should tell your doctor about any signs and symptoms such as new skin bumps or sores, changes in old skin problems, blood in the urine, painful urination, or persistent or blood-tinged mucous production.

If exposed to arsenic, you should ask your doctor about a proper schedule of skin examinations and also check your own skin each month. Based on the presence of other risk factors and the intensity and duration of arsenic exposure, your doctor might consider using other early detection testing, such as urine cytology (checking urine for cancer cells under a microscope), although available evidence does not firmly support such testing.

How Can I Avoid Exposure to Arsenic?

In Water

If you are concerned about the level of arsenic in your drinking water, know that information on arsenic levels is available. For public water systems, you can check the Consumer Confidence Reports issued annually or look for information on-line at the EPA’s Office of Water (http://www.epa.gov/safewater/arsenic/index.html) or at your state Environment Department. If you depend on private wells for water, you may have your water tested by private firms. If the level is unacceptably high, consider getting drinking water from another source. Remember that household water filters do not effectively remove arsenic.

At Work

If you currently work in an industry where arsenic exposure is a concern, the important ways to reduce or prevent exposures include:

• engineering changes, such as substituting safer materials for more hazardous materials, enclosing a process that may expose workers to hazards, or ventilating a work area 
• good work practices, such as changing clothes after work, washing work clothes regularly, and keeping food out of the work area 
• personal protective equipment, such as gloves and respirators, as part of a workplace protective program

For more information on preventing or reducing occupational exposures, speak with your company’s safety and health manager.

In Wood

Many, but not all, "pressure-treated" lumber products contain inorganic arsenic compounds that protect the wood against termites and fungi. Because relatively little arsenic escapes from the wood, these products have not been considered to be very dangerous. However, some scientists warn that it may be wise to use wood preservatives other than arsenic or to substitute wood with other building materials for children’s’ playground equipment. Some suggest that people (especially children) should avoid prolonged contact with dirt and sand beneath structures built with arsenic-treated wood. It is also recommended that anyone in prolonged contact with pressure treated wood, such as builders or children on a playground, thoroughly wash their hands with soap and water when done. Hand-to-mouth transfer is the most common way people are exposed to the arsenic in wood.

People may also be exposed to dangerous levels of arsenic by inhaling sawdust during construction. Acidic solutions help release the arsenic compounds from the wood and are not recommended for washing decks and other structures made with such products. You should avoid burning arsenic-treated lumber in stoves or open fires because this also releases dangerous levels of arsenic in smoke and ashes.

If you are concerned about arsenic exposures at work, from drinking water, from treated wood, or from other sources, you may contact specialists in environmental and occupational medicine. They can assess exposure levels, evaluate current health problems that may be related to the exposures, and give you information concerning future risk and how to minimize it. You can locate such qualified professionals and facilities by checking with the Association of Occupational and Environmental Clinics (http://www.aoec.org).

What’s the Bottom Line?

Many health problems have been linked to arsenic exposure. Strong scientific evidence shows that arsenic can cause cancer in humans. Inhaling arsenic increases the risk of lung cancer. Swallowing arsenic increases the risk of skin, bladder, and lung cancer. Based on this evidence, expert agencies have classified arsenic as a human carcinogen. Because of the cancer risk and other health hazards linked to arsenic, exposures to arsenic should be minimized.

Additional Resources

Other National Organizations and Web Sites

Agency for Toxic Substances and Disease Registry (ATSDR)
Internet Address: www.atsdr.cdc.gov/
The ToxFAQs^TM fact sheet for arsenic can be found at:
http://www.atsdr.cdc.gov/tfacts2.html

Association of Occupational and Environmental Clinics
Internet Address: http://www.aoec.org

Environmental Protection Agency (EPA)
General information on arsenic, including current regulatory issues, available at:
http://www.epa.gov/safewater/arsenic.html
Local drinking water information available at:
http://www.epa.gov/safewater/arsenic/index.html

International Agency for Research on Cancer (IARC)
Internet Address: http://www.iarc.fr/index.html

US Geologic Survey
Information on arsenic in U.S. ground water available at: http://water.usgs.gov/nawqa/trace/arsenic/

Other Publications

Buchet J, Lison D. Clues and uncertainties in the risk assessment of arsenic in drinking water. Food Chem Toxicol. 2000;38(suppl 1):S81-85.

Ferreccio C, Gonzalez C, Milosavjlevic V, et al. Lung cancer and arsenic concentrations in drinking water in Chile. Epidemiology. 2000;11:673-679.

Karagas MR, Tosteson TD, Blum J, et al. Design of an epidemiologic study of drinking water arsenic exposure and skin and bladder cancer risk in a US population. Environ Health Perspect. 1998;106(suppl 4):1047-1050.

Kurttio P, Pukkala E, Kahelin H, Auvinen A, Pekkanen J. Arsenic concentrations in well water and risk of bladder and kidney cancer in Finland. Environ Health Perspect. 1999;107:705-710.

Morales KH, Ryan L, Kuo TL, Wu MM, Chen CJ. Risk of internal cancers from arsenic in drinking water. Environ Health Perspect. 2000;108:655-661.

Pott WA, Benjamin SA, Yang RS. Pharmacokinetics, metabolism, and carcinogenicity of arsenic. Rev Environ Contam Toxicol. 2001;169:165-214.

Smith AH, Hopenhayn-Rich C, Bates MN, et al. Cancer risks from arsenic in drinking water. Environ Health Perspect. 1992;97:259-267.

Tiemann M. Arsenic in drinking water: Recent regulatory developments and issues. Congressional Research Service Report RS20672. September 14, 2000. Available at: http://www.cnie.org/nle/h2o-40.html.

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