Arsenic and Cancer Risk

What is arsenic?

Arsenic is a natural element in rocks and soil, water, air, and in plants and animals. People can also be exposed to arsenic in the environment from some agricultural and industrial sources.

Although it is sometimes found in its pure form as a steel grey metal, arsenic is usually part of chemical compounds:

• Inorganic compounds (arsenic combined with elements other than carbon): These compounds are found in industry, in building products (such as some “pressure-treated” woods), and in arsenic-contaminated water. This form of arsenic tends to be more toxic and has been linked to cancer.
• Organic compounds (arsenic combined with carbon and other elements): These compounds tend to be much less toxic than the inorganic arsenic compounds and are not thought to be linked to cancer. Organic arsenic compounds are found in some foods, such as fish and shellfish.

How are people exposed to arsenic?

Arsenic occurs naturally in the environment. We normally take in small amounts in the air we breathe, the water we drink, and the food we eat. People can also be exposed to arsenic in other ways, such as in some man-made products.

In food

For most people, food is their largest source of arsenic exposure, although much of this is likely to be in the less dangerous, organic form. The highest levels of arsenic (in all forms) in foods can be found in seafood, rice, rice cereal (and other rice products), mushrooms, and poultry, although many other foods, including some fruit juices, can also contain arsenic.

Rice is of particular concern because it is a major part of the diet in many parts of the world. It is also a major component of many of the cereals eaten by infants and young children. (Nearly all rice products have been found to contain at least some arsenic, although the levels can vary widely.)

In drinking water

Drinking water is an important and potentially controllable source of arsenic exposure. In parts of China, Taiwan, Bangladesh, and western South America, high levels of arsenic occur naturally in drinking water, and can be a major source of arsenic exposure.

Water in some areas of the United States, especially in the West, also naturally contains arsenic. Most US areas with higher levels of arsenic in drinking water are rural communities. (As discussed below, public drinking water systems in the US are required to test for arsenic and to keep it below a certain level.)

Natural arsenic levels tend to be higher in drinking water that comes from ground sources, such as wells, as opposed to water from surface sources, such as lakes or reservoirs.

At work

Arsenic has not been produced in the United States since 1985, although it is still imported from other countries. In the past, workers in smelters and in plants that manufactured, packaged, or distributed products that contained arsenic had high exposures from breathing in arsenic fumes and dust.

Arsenic was a common ingredient in many pesticides and herbicides in the past. People who made, transported, applied, or worked around these products might have been exposed to higher levels of arsenic. Inorganic arsenic compounds have not been used in pesticides in the US since 1993, and organic compounds were phased out of pesticides as of 2013 (with one exception used on cotton plants).

Today workplace exposure to arsenic can still occur in some occupations that use arsenic, such as copper or lead smelting, wood treating, and glass manufacturing. Regulations are in place to limit this workplace exposure.

In the community

People who live near current or former industrial or agricultural sources of arsenic can be exposed to higher levels by inhaling fumes or eating contaminated food.

Industrial buildings such as wood preservative and glass factories can contaminate nearby air, soil, and water. Communities near smelters, or near farm fields or orchards where arsenic pesticides were used, may also have contaminated soil.

Burning fossil fuels (such as coal) and tobacco can also release small amounts of arsenic into the air.

In pressure-treated wood

Some arsenic compounds, such as chromated copper arsenate (CCA), have been used as preservatives to help protect wood from rot and insects. CCA was used to pressure-treat lumber that was used in some home foundations, decks, fences, playgrounds (play sets), and other structures for many decades.

The use of CCA in pressure-treated lumber for most residential (home) uses was stopped in the US at the end of 2003, although it is still used for industrial purposes. This was done because of concerns that some of the arsenic might leach out of the wood and enter the soil or be absorbed through the skin when the wood is touched. Wood that is frequently touched by children, such as that found in some playground equipment, is a special concern.

People can also be exposed to arsenic by breathing in sawdust from cut arsenic-preserved wood or by breathing the smoke from burning this wood.

Pressure-treated lumber for residential use is now made with other compounds that do not contain arsenic. However, any structures built from lumber that was pressure-treated before 2004 may still contain CCA. (For more information, see “How can I limit my exposure to arsenic?”)

Does arsenic cause cancer?

In most cases, the American Cancer Society does not determine if something causes cancer (that is, if it is a carcinogen), but we do look to other respected organizations for help with this. Based on the available evidence, several expert agencies have evaluated the cancer-causing potential of arsenic.

International Agency for Research on Cancer (IARC) 

The IARC is part of the World Health Organization (WHO). One of its major goals is to identify causes of cancer.

IARC classifies arsenic (as a single element) and inorganic arsenic compounds (including arsenic trioxide, arsenite, and arsenate) as “carcinogenic to humans.” This is based on sufficient evidence in humans that these chemicals can cause:

• Lung cancer
• Bladder cancer
• Skin cancer

IARC also notes links in some studies to:

• Kidney cancer
• Liver cancer
• Prostate cancer

IARC classifies the organic arsenic compounds dimethylarsinic acid (DMA, also known as cacodylic acid) and monomethylarsonic acid (MMA) as “possibly carcinogenic to humans.”

IARC classifies other organic arsenic compounds as “not classifiable as to their carcinogenicity in humans.”

For more detailed information, see the IARC monograph Arsenic, Metals, Fibres, and Dusts.

The US National Toxicology Program (NTP) 

The NTP is an interagency program that includes the National Institutes of Health (NIH), the Centers for Disease Control and Prevention (CDC), and the Food and Drug Administration (FDA). In its most recent Report on Carcinogens, the NTP classifies arsenic and inorganic arsenic compounds as “known to be human carcinogens.”

For more detailed information, see the NTP’s Report on Carcinogens entry on Arsenic and Inorganic Arsenic Compounds.

US Environmental Protection Agency (EPA) 

The EPA maintains the Integrated Risk Information System (IRIS), an electronic database of human health effects from exposure to various substances in the environment. The EPA classifies inorganic arsenic as a “human carcinogen,” based on evidence in human studies of links to lung, bladder, kidney, skin, and liver cancers.

To learn more about the classification systems used by these agencies, see Determining if Something Is a Carcinogen and Known and Probable Human Carcinogens.

Other health effects of arsenic

Both short- and long-term exposure to arsenic can also cause other health problems. For example:

• Breathing in high levels of arsenic can cause a sore throat and irritated lungs.
• Swallowing high levels of arsenic can cause nausea, vomiting, diarrhea, muscle weakness and cramping, skin rashes, and other problems.
• Exposure to high enough amounts of arsenic can be fatal.
• Exposure to lower levels of arsenic over longer periods of time can cause skin changes, liver and kidney damage, and a shortage of red and white blood cells, which can lead to fatigue and an increased risk of infections.

Are arsenic levels regulated?

Because arsenic has been linked to cancer and other health effects, several US government agencies regulate arsenic levels and exposures, a few of which are described here.

In drinking water: The Environmental Protection Agency (EPA) has set a limit on the maximum level of arsenic allowed in US drinking water of 10 micrograms per liter (μg/L), or 10 parts per billion (ppb).

For bottled water, the Food and Drug Administration (FDA) has set a limit of 10 ppb.

In certain foods: There are no federal limits for arsenic in most foods, although the FDA has issued (or proposed) guidance for industry on limits (“action levels”) in certain foods that are more likely to contain arsenic. For example, the FDA has issued guidance to manufacturers to not exceed inorganic arsenic levels of 100 ppb in infant rice cereals. It has also issued guidance to not exceed inorganic arsenic levels of 10 ppb in apple juice. These are recommendations for manufacturers and are not legally enforceable limits.

In the community: The EPA has set limits on the amount of arsenic that industrial sources can release into the environment, and it has restricted the use of arsenic in pesticides.

At work: The Occupational Safety & Health Administration (OSHA), the federal agency responsible for health and safety regulations in most workplaces, limits workplace exposure to inorganic arsenic to 10 micrograms per cubic meter of air, averaged over an 8-hour period. When working at potentially higher exposure levels, OSHA requires employers to provide personal protective equipment such as respirators.

Can I limit my exposure to arsenic?

Arsenic is a naturally occurring element, so it’s not possible to avoid it completely. Most arsenic compounds have no smell or taste, so usually you can’t tell if arsenic is in your air, food, or water. Still, there are some things you can do that may lower your exposure.

In drinking water

Public drinking water systems in the US are required to test for arsenic and to keep it below a certain level (10 parts per billion, or ppb). If your drinking water comes from a public source, you can find out about the levels of certain substances in your drinking water, including arsenic, by contacting your local water system. You can also contact the EPA’s Safe Drinking Water Hotline at 1-800-426-4791 for information about drinking water safety.

If you get your water from a private source such as a well, you may want to have your water tested for arsenic levels by a reputable laboratory. People who live in areas with high levels of arsenic in the water may consider using alternative sources of drinking water, such as bottled water. Common household water filters do not effectively remove arsenic.

In foods 

Some foods naturally contain more arsenic than others. For example, the highest concentrations of arsenic have been found in seafood, although this is mainly in the less harmful organic form.

Rice and rice products are a particular concern because they are a major food source in many parts of the world and are included in the diets of many infants and children. The FDA has recommended that manufacturers limit inorganic arsenic in infant rice cereals to 100 ppb. Neither the FDA nor the American Academy of Pediatrics (AAP) recommend specific limits on how much rice or rice products should be eaten, but they do recommend that families eat a wide variety of foods for a well-balanced diet that includes grains other than rice, such as wheat, barley, and oats. This can help reduce any possible health effects from eating too much of any one type of food.

According to the FDA, cooking rice in larger amounts of water (similar to how pasta is cooked) can lower the amount of inorganic arsenic in rice by about half, but this type of cooking can also lower its nutrient value, especially for white rice. The FDA also notes that rinsing rice before cooking has very little effect on arsenic levels, and it can also lower its nutrient value.

Concerns have also been raised about arsenic levels in some fruit juices (particularly apple juice). The FDA has conducted routine testing for arsenic in apple juice for many years and has found that in general it has low levels of inorganic arsenic. Still, the FDA supports the USDA’s Dietary Guidelines for Americans, which recommends that infants under 1 year of age not drink fruit juice.

The AAP does not have specific recommendations regarding arsenic in fruit juices, but it has stated that children don’t need to drink fruit juice to have a well-balanced, healthy diet. Like the Dietary Guidelines for Americans, the AAP does not recommend fruit juice for infants younger than 12 months, because it offers no nutrition benefit at this age. The AAP also recommends limiting the intake of juice in younger children.

At work

If you are concerned about arsenic exposure in your workplace, discuss the situation with your employee health and safety representative or your employer. Ways to reduce or prevent exposure can include using personal protective equipment and using safer work practices. If needed, OSHA, the federal agency responsible for health and safety regulations in most workplaces, can provide more information or assistance.

From pressure-treated wood

Some pressure-treated lumber products contain an inorganic arsenic compound known as CCA. The sale of CCA-treated lumber for most residential (home) uses was stopped at the end of 2003. However, many structures such as home foundations, decks, fences, or playground play sets that contain CCA-treated lumber are still in use.

A special concern is the use of CCA-treated lumber around children, especially in play sets. Children might swallow small amounts of arsenic if they put their hands in their mouths after touching the wood or the soil around it.

If you aren’t sure if a wooden play set contains arsenic, contacting the manufacturer might help you find out. But if this information isn’t available, it’s safest to assume that it does.

To reduce exposure, the US Consumer Product Safety Commission (CPSC) recommends that parents and caregivers make sure children’s hands and other exposed body parts are thoroughly washed with soap and water after playing on all pressure-treated wood playground equipment. It has also been suggested that children not eat while on wooden playground equipment.

The CPSC also recommends that CCA-treated wood not be used where routine contact with food or animal feed can occur, such as in areas used to plant vegetables, fruits, or herbs. If you have a garden vegetable planter made with CCA-treated wood, put a plastic liner in it before filling it with soil to reduce exposure to CCA.

The CPSC also notes that regularly applying a sealant on existing CCA-treated lumber surfaces may lower the amount of arsenic released from the wood.

Arsenic can also be released into the air when cutting or burning CCA-treated lumber. If you are cutting pressure-treated lumber, it’s important to use proper safety equipment (including a mask) to limit your exposure, and to clean up any sawdust promptly. Do not burn pressure-treated lumber.

The EPA does not currently recommend removal of CCA-treated lumber, but if you decide to remove CCA-treated wood in a play set, deck, or other structure, contact the EPA or your state or local solid waste management offices to get instructions on how to dispose of it safely.

To learn more

Along with the American Cancer Society, other sources of information about arsenic include:

Centers for Disease Control and Prevention (CDC)
Arsenic Fact Sheet
ToxFAQs for Arsenic

Food and Drug Administration (FDA)
Arsenic in Food and Dietary Supplements: www.fda.gov/food/environmental-contaminants-food/arsenic-food-and-dietary-supplements
What You Can Do to Limit Your Exposure to Arsenic: www.fda.gov/food/environmental-contaminants-food/what-you-can-do-limit-exposure-arsenic

National Cancer Institute (NCI)
Arsenic: www.cancer.gov/about-cancer/causes-prevention/risk/substances/arsenic

National Toxicology Program (NTP)
Report on Carcinogens: Arsenic and Inorganic Arsenic Compounds: https://ntp.niehs.nih.gov/ntp/roc/content/profiles/arsenic.pdf

World Health Organization (WHO)
Fact Sheet on Arsenic: www.who.int/en/news-room/fact-sheets/detail/arsenic

Consumer Product Safety Commission (CPSC)
CCA-Pressure Treated Wood: www.cpsc.gov/s3fs-public/270_0.pdf