138Arsenic, 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.
Chronic oral exposure has resulted in gastrointestinal effects, anemia, peripheral neuropathy, skin
lesions, hyperpigmentation, and liver or kidney damage in humans. Inorganic arsenic exposure in
humans, by the inhalation route, has been shown to be strongly associated with lung cancer, while
ingestion of inorganic arsenic in humans has been linked to a form of skin cancer and also to
bladder, liver, and lung cancer. EPA has classified inorganic arsenic as a Group A, human
carcinogen.
Contamination of Groundwater
Arsenic contamination of groundwater is often due to naturally occurring high concentrations of
arsenic in deeper levels of groundwater. It is a high-profile problem due to the use of deep tubewells
for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people.
In addition, mining techniques such as hydraulic fracturing mobilize arsenic in groundwater and
aquifers due to enhanced methane 28 transport and resulting changes in redox conditions, and
inject fluid containing additional arsenic.
A 2007 study found that over 137 million people in more than 70 countries are probably affected
by arsenic poisoning of drinking water. Arsenic contamination of ground water is found in many
countries throughout the world, including the USA.
Approximately 20 incidents of groundwater arsenic contamination have been reported from all over
the world. Of these, four major incidents were in Asia, including locations in Thailand, Taiwan, and
Mainland China. In South America, Argentina and Chile are affected. There are also many locations
in the United States where the groundwater contains arsenic concentrations in excess of the
Environmental Protection Agency standard of 10 parts per billion adopted in 2001. Millions of
private wells have unknown arsenic levels, and in some areas of the US, over 20% of wells may
contain levels that are not safe.
Arsine
Arsine is a gas consisting of arsenic and hydrogen. It is extremely toxic to humans, with headaches,
vomiting, and abdominal pains occurring within a few hours of exposure. EPA has not classified
arsine for carcinogenicity.
Drinking water regulations require public water systems to monitor for arsenic at the entry point to
the distribution system. There is no federal requirement for systems to monitor for arsenic within
the distribution system. You may, however, want to test your distribution system water for arsenic
to be sure that the water being delivered has arsenic levels below the MCL. If you decide to monitor
your distribution system, consider testing for arsenic at locations where the settling and
accumulation of iron solids or pipe scales are likely (i.e., areas with cast iron pipe, ductile iron pipe,
or galvanized iron pipe).
If your water system has installed some form of arsenic treatment, keep in mind that the treatment
you installed may change the water quality in other ways. It might cause the water to react
differently in the distribution system. Depending on the kind of treatment you’ve installed, consider
what distribution system problems might result.