Arsenic is a naturally occurring
metalloid that is widely distributed in water, soil, air and biota from natural
and anthropogenic sources. Exposure to arsenic usually occurs via the
ingestion, inhalation and skin contact. Arsenic has been found in drinking
water in several countries worldwide which caused a major public health issue.
Cardiovascular, diabetes, and
cancers are some of the general health effects that result from exposure to
arsenic. There are three main groups of arsenic compounds inorganic, organic
and arsine gas. These groups are based on its valence state Arsenides/arsine gas with -3 oxidation
state,Metalloid arsenic with 0 oxidation state, Arsenite trivalent compound
with +3 oxidation state, and Arsenate pentavalent with +5 oxidation state.A better
understanding of the chemistry of arsenic is needed to identify its toxic
properties and its effects on humans and natural environment.
Oxidation states affect many
properties of arsenic such as soil adsorption, soil solubility and toxicity to
animals. Trivalent arsenic was dominant in the reducing conditions in flooded
soils while pentavalent arsenic at oxidizing conditions in drained soils.
Inorganic forms of arsenic are highly toxic compared to organic arsenic.
Organic arsenic includes methylated metabolites in three forms-
monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and trimethylarsine
oxide. Inorganic forms of arsenic are trivalent arsenite and pentavalent
arsenate.
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