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U.S. Geological Survey Fact Sheet 2005-3152

Arsenic in Coal

Arsenic is a persistent toxin that occurs naturally in trace amounts in rocks, sediments, and coal. Small amounts of arsenic may be present in ground water or, less commonly, surface waters, especially where there is a nearby source of arsenic. The most widespread natural source of arsenic is pyrite, a common mineral composed of iron and sulfur, which can contain a small amount of arsenic in its structure in place of sulfur.

Arsenic occurs in some ground-water aquifers due to chemical oxidation of pyrite or to reduction (the opposite of oxidation) of iron oxide minerals in the aquifer. Other sources of arsenic include past industrial activities, application of arsenic as a pesticide, and drainage from abandoned mine lands that contain pyrite. Prolonged consumption of drinking water from wells that greatly exceed arsenic health standards is the most serious arsenic-related health hazard in the United States and throughout the world.

Arsenic in bituminous coal occurs primarily in pyrite and, to a lesser extent, in organic portions of the coal. A small fraction of this arsenic is emitted during coal combustion. This Fact Sheet provides information on the arsenic content of U.S. coals, how arsenic occurs, and its behavior during mining, coal preparation, and coal combustion and in postcombustion beneficial uses.

  Interior view of residence in southwestern Guizhou Province, China, where arsenic-rich coal and coal briquettes are used to dry crops (chili peppers) that are later consumed, resulting in arsenic toxicity.

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  Interior view of residence in southwestern Guizhou Province, China, where arsenic-rich coal and coal briquettes are used to dry crops (chili peppers) that are later consumed, resulting in arsenic toxicity.

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