Arsenic is a trace element found in all human tissues. It is also a common heavy-metal poison that combines with intracellular proteins and is rapidly removed from the blood. It may become elevated when occupational (treated wood), environmental (coal burning), or intentional usage occurs. Sixty-three percent of ingested arsenic is excreted in the urine. Arsenic is found environmentally in well water and as an ingredient of pesticides, paints, treated wood, cosmetics, and antiprotozoal medications. Arsenic inhibits sulfhydryl enzyme systems required for cellular metabolism. Workplace exposure or chronic ingestion is associated with skin, lung and other cancers
Blood specimens are used for rapid confirmation of acute poisoning, and blood levels are transitory. Because it can be found in keratin, specimens of hair and nails are used to pinpoint chronic exposure to arsenic. Urine specimens are used for rapid confirmation of acute poisoning and monitoring ongoing exposure.