Use

Detection of nonacute arsenic exposure in hair specimens. Arsenic binds covalently to keratin in hair, reflecting exposure timing: hair from the nape of the neck documents recent exposure; axillary or pubic hair may reflect longer-term (6 months to 1 year) exposure. Elevated hair arsenic levels (> 1.00 mcg/g dry weight) may indicate excessive exposure; trace presence is normal. Hair arsenic concentration as high as 210 mcg/g dry weight was observed in a fatal chronic exposure case. Hair grows approximately 0.5 inch per month, with hair at the skin reflecting exposure ~1 week ago, and 1 inch distal representing ~2 months ago.