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The mechanisms of experimental external contamination which was obtained by immersing hair specimens in solution, especially the contamination through the airsac in medulla on cross section of hair was studied.The hair specimens which have medulla and obtained from one person were cut into the sections of 2cm in length. Untreated hair, the hair covered with Araldite on one end and the hair covered with Araldite on both ends were prepared. These hairs were contaminated externally by immersing them in NaCl solutions with sodium concentration of 9.4×104ppm and pH values of 7 and 11.1 for 1 hour and 24 hours. These contaminated hairs were cut into three portions along the major axis and sodium contents were determined by atomic absorption spectrometry. The distribution of sodium on the cross sections of other parts of the above specimens was determined by electron probe X-ray microanalyzer (XMA).XMA used was a JEOL SMU3-SDS. The operating conditions were 20KV acceleration voltage, 7.5-9.5×10-9A specimen current, RAP for Na-Kα as crystal and×500 magnification.The higher the pH value in immersing solution and the longer the immersing time, the higher the sodium contents in contaminated hair. One difference in sodium content was observed in the means of the three portions of untreated hair and the hair covered with Araldite on both ends which were immersed in the solution with pH value of 11 for 24 hours.As a result of XMA, gradual impregnations of sodium into the inner part of hair from outer layer were observed in the samples immersed in the solutions with pH value of 7 and 11 for 1 hour and all samples were impregnated with sodium into the medulla by the immersion for 24 hours. The higher the pH value, the faster the permeance. Especially higher sodium concentrations in medulla were observed in the samples immersed in the solution with pH value of 11 for 24 hours, regardless of the treatment with Araldite.It was thought that the higher sodium observed in the medulla of the hair covered with Araldite on both ends penetrated from cuticle of hair, because Araldite did not permeate NaCl solution. In addition, it was demonstrated that sodium penetrated also in the direction of hair axis, from the fact that in the hair covered with Araldite on both ends, sodium was detected also in the part of the hair covered entirely with Araldite.

Mechanisms of External Contamination of Human Hair Sample by Electron Probe X-Ray Microanalyzer