Potential sources and exposure

Arsenic

Cas No. 7440-38-2

Potential sources and exposure

Arsenic is a naturally occurring metal that has been widely used in rat and ant

poisons, herbicides, some medicines, and in arsenic treated (pressure treated)

wood. Some areas of the United States have unusually high natural levels of

arsenic in rock, which can lead to high concentrations in soil and water. Most

foods contain a low level of arsenic; however, seafood and freshwater fish

contain elevated levels of arsenic. There are several forms of arsenic to which an

individual might be exposed and the toxicity is dependent upon the type of

arsenic compound.

Physical and chemical properties

Property

Value

Molecular weight

74.92 g/mol

insoluble at 25 oC

Water solubility

Toxicity

The toxicity of arsenic depends upon its chemical form and route, dose, and

duration of exposure. In general, arsenites (AS3+) are more toxic than arsenates,

soluble arsenic compounds are more toxic than insoluble compounds, and

inorganic arsenic compounds are more toxic than organic derivatives (Agency

for Toxic Substances and Disease Registry (ATSDR) 1992).

Arsenic is an irritant of the skin, mucous membranes, and gastrointestinal

tract. Symptoms of acute toxicity include vomiting, diarrhea, convulsions, and a

severe drop in blood pressure. Subchronic exposures may result in

hyperpigmentation of the skin, persistent headache, and lethargy. Chronic

exposures to inorganic arsenic compounds may lead to neurotoxicity of both the

peripheral and central nervous systems as well as peripheral vascular disease and

skin lesions.

The most potent forms of the compound are the trivalent arsenic compounds.

These compounds can bind to sulfhydral groups on proteins and enzymes.

Arsenic affects mitochondrial enzymes and impairs tissue respiration, which

seems to be related to the cellular toxicity (Klaassen, Amdur, and Doull 1995).

Arsenic compounds are inducers of metallothionein which can serve a

detoxicating function.

The USEPA classifies arsenic as a known human carcinogen based on

epidemiological studies in which a causal association between exposure and skin

Appendix D Toxicological Profiles