The absorption of mercuric ion into single human head hairs

The concentration patterns of radioactive Hg++, Cu++, and I- in individual hair shafts, after soaking in aqueous solutions of these tracers, were measured nondestructively to permit repeated experiments on a given shaft. The mercury concentrations generally increased from the root end to the distal end of a given shaft less steeply than those of copper, while iodide concentrations generally decreased. Concentration peaks and other pattern features for mercury were also relatively less intense, but there was some correlation of the position of such areas of increased mercury, copper, and iodine adsorption in a given shaft. At equilibrium after more than 100 h of soaking, the amount of mercury taken up at pH 8 by the hair was three to four times that at pH 3. The rate of absorption of mercury was higher at low pH values, and that of desorption higher at high pH values. The relative intensity of pattern features remained constant during absorption or desorption at a given pH, but changed if the pH was changed. These data are discussed in terms of the chemistry of the hair binding sites for cations and anions.