Several hundred samples of human head hair were analyzed to establish the range and variation of mercury concentration in
“normal” people and in persons ingesting organic mercury compounds. Instrumental neutron activation analysis was used. The
77 keV line of197Hg was counted on a Ge(Li) detector. The pattern of concentration variation along hair was shown to be a more reliable criterion
for hair individualization than average concentration values. The hair mercury contents of “normal” people in uncontaminated
areas were 0.1–4 and 1–12 ppm, respectively. People who had ingested a mercury compound but showed no symptoms had hair mercury
concentrations of from a few ppm to 300 ppm. Mild symptoms appeared with a 120–600 ppm hair mercury level, moderate with 200–800
ppm, and severe with 400–1600 ppm. There was no correlation with sex or age, except that infants showed more severe symptoms
than expected, and people over 55 had mild or no symptoms with hair mercury levels of 1000 ppm and higher.