277Arsenic- Inorganic Contaminant 0.010 mg/L MCL
Metalloid See Arsenic in IOC Section for more information
Arsenic is a chemical element with symbol As and the atomic number is 33. Arsenic occurs
in many minerals, usually in conjunction with sulfur and metals, and also as a pure
elemental crystal. It was first documented by Albertus Magnus in 1250. Arsenic is a
metalloid. It can exist in various allotropes, although only the
gray form has important use in industry.
In 1974, Congress passed the Safe Drinking Water Act. This
law requires EPA to determine the level of contaminants in
drinking water at which no adverse health effects are likely to
occur. These non-enforceable health goals, based solely on
possible health risks and exposure over a lifetime with an
adequate margin of safety, are called maximum contaminant
level goals (MCLG). Contaminants are any physical, chemical,
biological or radiological substances or matter in water.
The MCLG for arsenic is zero. EPA has set this level of
protection based on the best available science to prevent
potential health problems. Based on the MCLG, EPA has set
an enforceable regulation for arsenic, called a maximum
contaminant level (MCL), at 0.010 mg/L or 10 ppb. MCLs are
set as close to the health goals as possible, considering cost,
benefits and the ability of public water systems to detect and
remove contaminants using suitable treatment technologies.
The Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring
Final Rule, the regulation for arsenic, became effective in 2002. The Safe Drinking Water
Act requires EPA to periodically review and revise contaminants, if appropriate, based on
new scientific data. The regulation for arsenic will be included in a future review cycle.
The main uses of metallic arsenic is for strengthening alloys of copper and especially lead
(for example, in car batteries). Arsenic is a common n-type dopant in semiconductor
electronic devices, and the optoelectronic compound gallium arsenide is the most
common semiconductor in use after doped silicon. Arsenic and its compounds, especially
the trioxide, are used in the production of pesticides (treated wood products), herbicides,
and insecticides. These applications are declining, however.
Arsenic is notoriously poisonous to multicellular life, although a few species of bacteria
are able to use arsenic compounds as respiratory metabolites. Arsenic contamination of
groundwater is a problem that affects millions of people across the world.
Arsenic, a naturally occurring element, is found throughout the environment; for most
people, food is the major source of exposure. Acute (short-term) high-level inhalation
exposure to arsenic dust or fumes has resulted in gastrointestinal effects (nausea,
diarrhea, abdominal pain); central and peripheral nervous system disorders have occurred
in workers acutely exposed to inorganic arsenic. Chronic (long-term) inhalation exposure
to inorganic arsenic in humans is associated with irritation of the skin and mucous
membranes.