Uranium and thorium in human hair from young Spanish adults (20-24 years old).

Human hair can be considered an appropriate matrix to assess chronic exposure to some natural radionuclides. Thus, hair has been suggested as a substitute for urine to determine chronic exposure to uranium as its presence is much higher in hair. However, there is little information about the exposure to relevant radionuclides in the Spanish population. We have determined the content of uranium-238 (U) and thorium-232 (Th) in scalp hair from 37 volunteers (20 to 24 years-old; 28 female and 9 male) from the Comunidad de Madrid (Spain). U and Th were monitored by ICP-MS after appropriate removal of exogenous contamination with Triton X-100. The limits of detection were: U (1.08 ng/g) and Th (0.47 ng/g). The hair concentrations were as follows (median and percentiles are provided in ng/g, for male and female participants, respectively): U [63.15 (31.29, 188.64) vs. 83.23 (22.13, 179.70)] and Th [2.35 (1.10, 7.11) vs. 1.49 (1.17, 3.35)]. Presence of these radionuclides did not show dependency due to sex, and were within reference ranges provided for a general Swedish population. Large variation was observed in the levels of both elements from one individual to another, which is in line with previous studies and could be due to a myriad of different exposures to U and Th in this population. However, the concentrations found in the Spanish participants’ hair were higher, although within the same order as those described in adults that live in areas with a high natural background of U and Th (Serbia and China). Our results, although preliminary, might indicate a moderate presence of U and Th in the environment in the Comunidad de Madrid that should be investigated in conjunction with identification of exposure pathways to assess risks to human health due to chronic exposure to these radionuclides.