Exogenous contamination of uranium in human scalp hair

The use of human scalp hair as a bioindicator of occupational or environmental exposure has been the subject of some debate over the years. One problem is how to distinguish internal contamination from external contamination. In this study, possibility that elevated levels of natural uranium in human hair are partly due to the exogenously bound uranium from uranium-rich household water was tested. Hair samples from six adult volunteers were cut and then exposed externally to uranium by using washing water with highly elevated levels of natural uranium. After that, and before making the analysis using inductively coupled plasma mass spectrometry (ICP-MS), the samples were washed using two commonly used washing procedures in order to remove external contamination. No quantitative information was gained in the tests, but it was shown that the use of uranium-rich water when washing hair affects the uranium concentration in hair. Although the samples were cleaned according to widely used washing procedures before the analysis, the uranium concentrations in hair were about three orders of magnitude higher after the tests. The possibility of external contamination should be kept in mind, especially when considering hair as an excretion pathway for estimating internal dose.