|Values are valid only on day of printing.|
Arsenic circulating in the blood will bind to protein by formation of a covalent complex with sulfhydryl groups of the amino acid cysteine. Keratin, the major structural protein in hair and nails, contains many cysteine residues and, therefore, is one of the major sites for accumulation of arsenic. Since arsenic has a high affinity for keratin, the concentration of arsenic in nails is higher than in other tissues.
Several weeks after exposure, transverse white striae, called Mees' lines, may appear in the fingernails.
Detection of nonacute arsenic exposure
Nails grow at a rate of approximately 0.1 inch/month. Nail keratin synthesized today will grow to the distal end in approximately 6 months. Thus, a nail specimen collected at the distal end represents exposure of 6 months ago.
Nail arsenic >1.00 mcg/g dry weight indicates excessive exposure. It is normal for some arsenic to be present in nails, as everybody is exposed to trace amounts of arsenic from the normal diet.
The highest hair or nail arsenic observed at Mayo Clinic was 210 mcg/g dry weight in a case of chronic exposure that was the cause of death.
0-15 years: not established
> or =16 years: 0.0-0.9 mcg/g of nails
Hindmarsh JT, McCurdy RF: Clinical and environmental aspects of arsenic toxicity. Crit Rev Clin Lab Sci 1986;23:315-347