Trace-element content of human scalp hair

The importance of some of the factors that could affect the measured trace-element content of human scalp hair have been evaluated. Included are frequency of hair washing and swimming, shampoos used, gross differences in diet, and the variation in content along the strands of hair. The data for length-content variation suggest that, for some elements, eccrine sweat may contribute significantly to the measured trace-element content of hair and that such variation must be taken into account in assessing data for historical hair samples, many of which represent clippings of distal segments of hair