Caveats in hair analysis in chronic arsenic poisoning

The diagnosis and evaluation of chronic arsenic poisoning remains a difficult task. Clinical indicators are crude measures, and electromyography adds little to the picture. Blood arsenic levels are transitory, however urine levels are useful for monitoring ongoing exposure. Hair arsenic is useful as a confirmatory feature in chronic arsenic poisoning provided external contamination by arsenic can be excluded. The distribution of arsenic in cross sections or along the length of a shaft of hair cannot distinguish external contamination from arsenic derived from ingestion.