Arsenic is a naturally occurring element found in low concentrations in rocks, soils, water, plants, and animals. In Kentucky, arsenic is commonly found in iron sulfide minerals associated with coal deposits and black shales. Arsenic is released when iron sulfides oxidize during weathering. Once released, it is readily sorbed onto iron oxides and iron oxyhydroxides, which limits arsenic concentrations in the near-surface environment.
Arsenic is used as a wood preservative and in paints, dyes, metals, drugs, soaps, semiconductors, animal feed additives, and herbicides. From 1860 through 1910 arsenic was heavily used in embalming fluids. It was banned in 1910 because it interfered with investigations into suspected poisoning deaths; old graveyards may still be a source of arsenic in groundwater. Waste-disposal sites and landfills may be sources of arsenic contamination because of the materials disposed of there, and coal combustion can release arsenic to the atmosphere. Hydrocarbons from leaking underground storage tanks can dissolve iron oxide minerals in soils, thus releasing naturally occurring arsenic to the environment.
Long-term exposure to arsenic in drinking water has been linked to health problems such as cancer of the skin, bladder, lungs, kidneys, nasal passages, liver, and prostate. Arsenic has also been linked to damage of the cardiovascular, pulmonary, immunological, neurological, and endocrine systems. Because of these health effects, the U.S. Environmental Protection Agency set the maximum contaminant level (MCL) for arsenic in drinking water at 50 parts per billion in 1974. In 2001 the EPA announced that this MCL will be lowered to 10 parts per billion. Water-supply systems must meet the new MCL by January 2006.
A map of the state shows the geographic distribution of arsenic concentrations, and a table shows the concentrations according to physiographic region. The map shows that arsenic in Kentucky groundwater generally does not exceed the MCL, and there are no widespread occurrence of high arsenic concentrations. Some regions of the Commonwealth are more likely to have high arsenic concentrations in groundwater than others, however. These findings should be viewed as general patterns.