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Arsenic: An Abundant Natural Poison
(Released March 2009)

 
  by Andreas Saldivar & Vicki Soto  

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Toxicology

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While arsenic occurs in both organic and inorganic compounds, the two types behave differently in the human body. Organic arsenic compounds are not metabolized easily and, when ingested, are excreted unchanged. (ATSDR 2007) Inorganic compounds of arsenic are metabolized, forming monomethylarsonic acid and dimethylarsinic acid.

Human exposure to inorganic arsenic can occur in several different ways: Dermal or skin exposure, inhalation, and ingestion. Inorganic arsenic is classified as a Class A Carcinogen, or Human Carcinogen, by the U.S. Environmental Protection Agency when exposure is ingestion or inhalation. (U.S. Environmental Protection Agency 1998)

chemical chart
SAHC = S-adenosylhomocysteine; SAM = S-adenosylmethionine Source

Dermal/skin exposure: may result in skin irritation with local redness and/or swelling but has no permanent toxic effects. (ATSDR 2007)

Inhalation: exposure of this kind can be occupational, such as refinery workers and farmers. Exposure of greater than .75 mg/m3 is associated with a greater risk of lung cancer. (World Health Organization, 2001) (ATSDR 2007)

feet with lesions
Skin Lesions
Ingestion: Large doses (from 50 to 300 mg) of ingested arsenic are fatal. (ATSDR 2007) Smaller doses can come from food and/or drinking water and cause "symptoms such as stomachache, nausea, vomiting, and diarrhea" as well as "decreased production of red and white blood cells, which may cause fatigue, abnormal heart rhythm, blood-vessel damage resulting in bruising, and impaired nerve function causing a 'pin and needles' sensation in your hands and feet." (ATSDR 2007) Long term exposure - from 5 to 15 years - can lead to various cancers including bladder, liver, lung and skin. Other skin diseases may develop including patches of roughened skin on the palms and soles, which can be a hallmark of chronic exposure. (ATSDR 2007) (World Health Organization 2001)

Arsenic is mainly excreted from the body through urine within 1 to 2 days. (ATSDR 2007) Indicators of exposure to arsenic can be measured in urine but can also occur in hair, nails and blood. Arsenic levels in blood can only determine relative recent exposures since arsenic is removed from blood very quickly. (ATSDR 2007) Hair and nails can show past exposure if exposure occurred during their growth cycle. Hair may show relative time-since-exposure but care must be taken to not have external influence of adsorbed arsenic from the air. (World Health Organization, 2001) (ATSDR 2007)

Naturally occurring dissolved forms of inorganic arsenic are found in drinking water supplies and make up many of the possible sources of human exposure. Arsenicosis—or arsenic poisoning—occurs after chronic or long term exposure to arsenic contaminated drinking water. Naturally occurring arsenic compounds appear in much of the world's water supply in small amounts. Higher concentrations of arsenic compounds in groundwater do appear in various countries including the USA, Thailand, China, India, Argentina, Nepal and Bangladesh. (World Health Organization 2008)

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