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ToxFAQs™: Chemical Agent Briefing Sheets (CABS)

January 2006

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What is arsenic?

Arsenic is an element that is widely distributed in the earth's crust. Elemental arsenic is a steel grey metal-like material. Arsenic is usually found in the environment combined with other elements, such as oxygen, chlorine, and sulfur. It is released into the air by volcanoes, through weathering of arsenic-containing minerals and ores, especially near geothermal activity, and by commercial or industrial processes. In industry, arsenic is a by-product of the smelting process for many metal ores, including lead, gold, zinc, cobalt, and nickel.

What are the forms of arsenic?

Arsenic is found in two forms:

The inorganic forms are more toxic than the organic ones.

Form Chemical Formula Name

Common valence states

metalloid arsenic
such as arsenites
such as arsenates
such as arsine gas

Examples of organic arsenicals

cacodylic acid (dimethylarsinic acid)
disodium methylarsenate (DSMA)

Examples of inorganic arsenicals

arsenic acid
disodium arsenate
sodium arsenite

What are the common uses of arsenic?

Commercial products

  • antifouling paints
  • cattle and sheep dips
  • cotton desiccants
  • fire salts (multicolored flame)
  • fungicides
  • herbicides (weed killers and defoliants)
  • insecticides
  • leaded gasoline
  • paints and pigments
  • wood preservatives

Industrial processes

  • bronze plating
  • clarifying glass and ceramics
  • electronics manufacturing
    • microwave devices
    • lasers
    • light-emitting diodes
    • photoelectric cells, and
    • semiconductor devices
  • hardening metal alloys
  • preserving animal hides
  • purifying industrial gases (removal of sulfur)

Medicines and remedies

  • Antiparasitic drugs (carbasone - C7H9AsN2O4)
  • Donovan's solution (arsenic triiodide - AsI3)
  • Folk remedies ("Asiatic pill," kushtay, yellow root)
  • Fowler's solution (1% solution of potassium arsenite – [K3AsO3])
  • Kelp-containing health foods
  • Some naturopathic remedies

What are the routes of exposure for arsenic?


  • The estimated average daily dietary intake of total arsenic by adults in the United States is 50 milligrams per day.
    • Meat, fish, and poultry account for 80% of dietary arsenic intake.
    • Fish, seafood, and algae also contain high concentrations of arsenic in the form of arsenobetaine and arsenocholine, sometimes referred to as "fish arsenic."
      • Fish arsenic has low toxicity to humans and is rapidly excreted in urine.
    • Wine produced in vineyards that were sprayed with arsenic-containing pesticides may have appreciable levels of arsenic.


  • Smokers may inhale small amounts of arsenic because of past application of arsenic-containing pesticides on tobacco leaves.

Drinking Water

  • Exposure to arsenic in drinking water is a problem in some regions of the United States, Mexico, India, and regions of Asia.
  • Well water contaminated by natural sources such as arsenic-containing bedrock has been reported to be the leading cause of arsenic toxicity throughout the world, including areas of the United States.
  • The areas in the United States with the highest natural groundwater concentrations of arsenic are New England, the Southwest, the Northwest, Alaska, and areas near geothermal activity.
  • Groundwater may contain elevated concentrations of arsenic due to contamination from runoff of arsenic-containing pesticides from past use.
  • Arsenic has been detected in both surface water and groundwater, at average concentrations of 40 and 47 parts per billion (ppb), respectively, in about 15% of hazardous waste sites studied by ATSDR.

What are the possible toxic effects of arsenic?

Most of the toxic effects arise from exposure to inorganic arsenic. Because it targets a number of metabolic processes, arsenic affects nearly all organ systems of the body.


  • Arsenic is known to cause cancer in humans.
  • Ingested inorganic arsenic is strongly associated with lung and skin cancers and may cause other cancers in organs such as the bladder, kidneys, and liver.
  • Skin cancer associated with eating or drinking of inorganic arsenic may take more than 1 year to develop; noncarcinogenic skin effects typically develop weeks or months after exposure.
  • The number of deaths among workers exposed by inhalation to inorganic arsenic increases with the duration and intensity of exposure.


  • Acute arsenic poisoning may cause internal bleeding (diffuse capillary leak) and inflammation of the heart (cardiomyopathy), resulting in shock.
  • Long-term ingestion of arsenic in drinking water has resulted in pronounced changes in blood vessels outside the heart and brain.


  • Seen primarily after acute and short-term arsenic ingestion.


  • Acute poisoning may cause renal failure.


  • Eating or drinking of inorganic arsenic may kill liver cells and elevate levels of liver enzymes.


  • Arsenic-exposure can destroy a person’s nerve cells, leading to nervous system disorders (peripheral neuropathy).


  • Lung cancer deaths among exposed workers increase with their duration and intensity of exposure.


  • Increased frequency of spontaneous abortions and congenital malformations has been linked to arsenic exposure.


  • Inhaling high concentrations of arsenic compounds irritates the lining of the nose, throat, and lungs.


  • Bone marrow depression (an inability to make certain blood cells) may result from arsenic poisoning and may first appear as a shortage of all types of blood cells.
    • Note: Unlike other forms of arsenic, arsine gas causes a hemolytic syndrome (destruction of red blood cells.)


  • Pigment changes and thickening of the skin on hands and feet (palmoplantar hyperkeratosis) are characteristic of chronic (long term) arsenic exposure.
  • Skin cancer associated with eating or drinking arsenic may take 30 to 40 years to develop.
  • Noncarcinogenic skin effects typically develop several years after exposure.
  • Skin thickening caused by arsenic may later become malignant.

What are the safety guidelines for arsenic exposure?

Source Guidelines


  • Arsenic is listed by the U.S. Environmental Protection Agency (EPA) as a hazardous air pollutant (HAP).
    • HAPs are substances that may increase mortality or serious illness in humans after significant exposure.
  • EPA National Emissions Standards for Hazardous Air Pollutants limit emissions of inorganic arsenic from
    • primary copper smelters
    • glass-manufacturing plants
    • arsenic plants
  • However, there is no ambient federal air standard for arsenic.

Drinking water

  • The EPA Office of Drinking Water has set a maximum contaminant level (MCL) for arsenic in drinking water of 10 ppb.
  • The World Health Organization recommends a provisional drinking water guideline of 10 ppb (0.01 mg/L) as a practical limit.


  • The U.S. Food and Drug Administration (FDA) has established tolerance levels for arsenic in by-products of animals treated with veterinary drugs. These permissible levels range
    • from 0.5 parts per million (ppm) in eggs and uncooked edible tissues of chickens and turkeys
    • to 2 ppm in certain uncooked edible by-products of pigs and others.


  • EPA began to phase out household ant poisons containing sodium arsenate in 1989 because of the danger of ingestion by small children.
  • EPA also cancelled all registered uses of inorganic arsenic for nonwood preservative purposes.
  • Pressure-treated wood with chromium-copper-arsenic (CCA) has been phased out for residential use.

What are the minimal risk levels (MRL) for arsenic exposure?

An MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse non-cancer health effects over a specified duration of exposure.

ATSDR Minimal Risk Levels (MRLs), December 2005
Name Route Duration MRL Factors Endpoint
Arsenic Oral Acute 0.005 mg/kg/day* 10 Gastrointestinal
Chronic 0.0003 mg/kg/day 3 Dermal
*Provisional; mg/kg/day = milligrams per kilogram of body weight per day

What are the most important or common mediating factors?

The factors that determine how severe the health effects are from arsenic exposure include:

What are the body’s defense systems against arsenic?

Is there a test to see if my child or I have been exposed to arsenic?

A key laboratory test in recent exposures to arsenic is urinary excretion of inorganic and methylated arsenic metabolites.

Because urinary levels of arsenic may drop rapidly in the first 24 to 48 hours after short-term exposure, the laboratory needs to obtain a urine specimen for arsenic analysis promptly. Depending on the patient's clinical state, tests may include the following:

Measurement of arsenic levels in hair and nails may be a useful indicator of past or lengthy exposures. Because arsenic may be adsorbed to the external surface, hair and nail samples should be washed before testing.

Future research needs

Environmental fate

  • Additional quantitative data on the rates of oxidation, reduction, and biotransformation reactions of arsenic compounds, and how these depend on environmental conditions would help in evaluating and predicting the fate and transport of arsenic at hazardous waste sites and other areas.

Bioavailability from environmental media

  • Further data would be useful to establish whether arsenic uptake occurs from contact with contaminated soil or water, since these routes near hazardous waste sites may expose humans.

Food chain bioaccumulation

  • Further research on the uptake of arsenic by plants in a wide range of arsenic-polluted sites (e.g., mining areas, orchards previously treated with lead arsenate) would be valuable in assessing human exposure near such sites from eating vegetables from home gardens.

Exposure levels in environmental media

  • Additional monitoring studies that include identification of arsenic species would allow more precise estimation of current exposure levels and possible human health risks.
  • Reliable monitoring data for the levels of arsenic in contaminated media at hazardous waste sites are needed. Information obtained on levels of arsenic in the environment could be used in combination with the known body burdens of arsenic to assess the potential risk of adverse health effects in people living near hazardous waste sites.

Exposures of children

  • Additional studies, including investigations of unique pathways for exposures of children and the amount of soil a child ingests, would provide valuable data.
  • Studies are needed to assess whether children are different in their weight-adjusted intake of arsenic.

For more information






For more information, contact:

Agency for Toxic Substances and Disease Registry
Division of Toxicology and Environmental Medicine
1600 Clifton Road NE, Mailstop F-32
Atlanta, GA 30333
Phone: 1-800-CDC-INFO (800-232-4636)
TTY 888-232-6348

FAX: (770)-488-4178

This page was updated on 01/04/2008