Arsenic is an element that occurs naturally in the environment, almost always in combination with other elements to form arsenic compounds. Some of those compounds are more toxic than others. Technically arsenic is a metalloid because it has properties of both metals and nonmetals, but it is usually referred to as a metal. Arsenic has been used in wood preservatives, pesticides (especially on cotton and in orchards), lead-acid batteries, some electronic components, and in some specialized industrial applications, though its use has diminished due to concerns about its health effects.
Environmental Fate and Transport
Arsenic persists in the environment and cannot be destroyed, though it may form different compounds over time. Arsenic emitted into the air (for example, from coal burning power plants) may travel long distances before settling onto the earth's surface. Arsenic in and on the soil usually stays there unless moved. However, some arsenic compounds are soluble and can end up in surface water or groundwater. Most arsenic in surface water bodies eventually ends up in the sediment at the bottom of those bodies. Some fish and shellfish can accumulate arsenic in their bodies, though usually in arsenic compounds that are less toxic than most other arsenic compounds.
Because arsenic is a natural part of the environment, we are all exposed to arsenic to some extent. Ingestion of soil or dust (especially by children) results in some arsenic exposure; the extent of that exposure depends on the amount consumed and the concentration of arsenic in the soil or dust, which can vary widely depending on location. The same is true for drinking water that contains arsenic. Most groundwater contains very little arsenic, but levels in groundwater (or soil) can be very high in areas with naturally high levels of arsenic or contamination from previous activities. Potentially important dietary sources of arsenic include seafood, rice and rice products, mushrooms, and poultry. Fortunately, most dietary arsenic exposure is to less toxic arsenic compounds.
Most ingested arsenic readily enters the body. Arsenic that enters the lungs may be absorbed into the bloodstream. Most of the arsenic that you touch will probably not enter your body. Arsenic is usually excreted in urine within a few days, though inorganic arsenic can remain for longer, sometimes much longer.
The ancients knew that arsenic is poisonous, and that large doses can be fatal. Effects observed from lower doses include digestive tract irritation, reduced blood cell formation, fatigue, cardiac arrhythmia, nerve damage, blood vessel damage, and a variety of skin problems, including skin cancer. Arsenic is a known human carcinogen.
The preceding paragraphs are summarized from the Public Health Statement for Arsenic published by the Agency for Toxic Substances and Disease Registry.
Additional Cancer Assessments
U.S. EPA's Integrated Risk Information System states that arsenic is a human carcinogen.
The National Institutes of Health has determined that arsenic and inorganic arsenic compounds are known to be human carcinogens.
The International Agency for Research on Cancer has determined that "There is sufficient evidence in humans for the carcinogenicity of mixed exposure to inorganic arsenic compounds, including arsenic trioxide, arsenite, and arsenate. Inorganic arsenic compounds, including arsenic trioxide, arsenite, and arsenate, cause cancer of the lung, urinary bladder, and skin. Also, a positive association has been observed between exposure to arsenic and inorganic arsenic compounds and cancer of the kidney, liver, and prostate." (IARC, page 85).