278Chronic 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.