Title: Arsenic - Wikipedia
Headings: Arsenic
Arsenic
Contents
Characteristics
Physical characteristics
Isotopes
Chemistry
Compounds
Inorganic compounds
Alloys
Organoarsenic compounds
Occurrence and production
History
Applications
Agricultural
Medical use
Alloys
Military
Other uses
Biological role
Bacteria
Essential trace element in higher animals
Heredity
Biomethylation
Environmental issues
Exposure
Occurrence in drinking water
San Pedro de Atacama
Hazard maps for contaminated groundwater
Redox transformation of arsenic in natural waters
Wood preservation in the US
Mapping of industrial releases in the US
Bioremediation
Toxicity and precautions
Classification
Legal limits, food, and drink
Reducing arsenic content in rice
Occupational exposure limits
Ecotoxicity
Toxicity in animals
Biological mechanism
Exposure risks and remediation
Treatment
See also
References
Bibliography
Further reading
External links

Content: A few species of bacteria are able to use arsenic compounds as respiratory metabolites. Trace quantities of arsenic are an essential dietary element in rats, hamsters, goats, chickens, and presumably other species. A role in human metabolism is not known. However, arsenic poisoning occurs in multicellular life if quantities are larger than needed. Arsenic contamination of groundwater is a problem that affects millions of people across the world. The United States ' Environmental Protection Agency states that all forms of arsenic are a serious risk to human health. The United States' Agency for Toxic Substances and Disease Registry ranked arsenic as number 1 in its 2001 Priority List of Hazardous Substances at Superfund sites. Arsenic is classified as a Group-A carcinogen. Contents
1 Characteristics
1.1 Physical characteristics
1.2 Isotopes
1.3 Chemistry
2 Compounds
2.1 Inorganic compounds
2.1.1 Alloys
2.2 Organoarsenic compounds
3 Occurrence and production
4 History
5 Applications
5.1 Agricultural
5.2 Medical use
5.3 Alloys
5.4 Military
5.5 Other uses
6 Biological role
6.1 Bacteria
7 Essential trace element in higher animals
7.1 Heredity
7.2 Biomethylation
9 Toxicity and precautions
9.1 Classification
9.2 Legal limits, food, and drink
9.2.1 Reducing arsenic content in rice
9.3 Occupational exposure limits
9.4 Ecotoxicity
9.5 Toxicity in animals
9.6 Biological mechanism
9.7 Exposure risks and remediation
9.8 Treatment
10 See also
11 References
12 Bibliography
13 Further reading
14 External links
Characteristics
Physical characteristics
Crystal structure common to Sb, AsSb and gray As
The three most common arsenic allotropes are gray, yellow, and black arsenic, with gray being the most common. Gray arsenic (α-As, space group R 3 m No.