As with other heavy metals, Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is used to quantitate arsenic levels in specimens.
Blood arsenic:
Whole blood concentrations of arsenic are elevated for a short time after exposure. Arsenic levels decline rapidly in the blood as arsenic binds to proteins and is sequestered in tissue. The half-life of inorganic arsenic in blood is 4-6 hours, while the half-life of methylated metabolites is 20-30 hours. Because of its short half-life, arsenic is not likely to be detected in blood specimens collected more than 48 hours after exposure. For this reason, blood is not the preferred specimen to screen for arsenic toxicity.
Urine arsenic:
Urine is the preferred specimen for arsenic testing. Organic arsenic is eliminated from the body within 1-2 days of ingestion. As5+ is reduced to the less toxic As3+ form in the liver. As3+ and As5+ are present in the urine shortly after ingestion, whereas their methylated metabolites will peak in urine 20-60 hours after ingestion and return to baseline 1-3 weeks later.
Hair and nail arsenic:
Like lead, arsenic can be measured in hair and nail samples to ascertain longer, chronic exposure incidents or past exposures. Since hair grows about half an inch per month, hair keratin synthesized by hair follicles will protrude through the skin (as hair) in about one week. Thus, each inch of hair from the skin represents about eight weeks in the past.
