141Occurrence and Production
Minerals with the formula MAsS and MAs 2 (M = Fe, Ni, Co) are the dominant commercial sources
of arsenic, together with realgar (an arsenic sulfide mineral) and native arsenic. An illustrative
mineral is arsenopyrite (FeAsS), which is structurally related to iron pyrite. Many minor As-
containing minerals are known. Arsenic also occurs in various organic forms in the environment.
Inorganic arsenic and its compounds, upon entering the food chain, are progressively metabolized
to a less toxic form of arsenic through a process of methylation.
Other naturally occurring pathways of exposure include volcanic ash, weathering of arsenic-
containing minerals and ores, and dissolved in groundwater. It is also found in food, water, soil,
and air. Arsenic is absorbed by all plants, but is more concentrated in leafy vegetables, rice, apple
and grape juice, and seafood. An additional route of exposure is through inhalation.
In 2005, China was the top producer of white arsenic with almost 50% world share, followed by
Chile, Peru, and Morocco, according to the British Geological Survey and the United States
Geological Survey. Most operations in the US and Europe have closed for environmental reasons.
The arsenic is recovered mainly as a side product from the purification of copper. Arsenic is part of
the smelter dust from copper, gold, and lead smelters.
On roasting in air of arsenopyrite, arsenic sublimes as arsenic (III) oxide leaving iron oxides, while
roasting without air results in the production of metallic arsenic. Further purification from sulfur and
other chalcogens is achieved by sublimation in vacuum or in a hydrogen atmosphere or by
distillation from molten lead-arsenic mixture.
Health Hazard Information
Arsenic Applications.........................
Arsenic is known to cause cancer, as well as many other serious health problems. Here we
review the hazards of arsenic exposure and ways people can protect themselves from these
hazards.
Arsenic is an element in the environment that can be found naturally in rocks and soil, water, air,
and in plants and animals. It can also be released into the environment from some agricultural
and industrial sources.
Arsenic has no taste or smell. Although sometimes found in its pure form as a steel grey metal,
arsenic is usually part of chemical compounds. These compounds are divided into 2 groups:
Inorganic compounds (combined with oxygen, iron, chlorine, and sulfur)
Organic compounds (combined with carbon and other atoms)
Inorganic arsenic compounds are found in industry, in building products (in some "pressure-
treated" woods), 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 are much less toxic than the inorganic arsenic compounds and are
not thought to be linked to cancer. These compounds are found in some foods, such as fish and
shellfish.
While arsenic levels may fluctuate over time, what is most significant from the standpoint of
cancer risk is long-term exposure.