THE STUDY OF HUMAN NAILS AS AN INTAKE MONITOR FOR ARSENIC USING NEUTRON-ACTIVATION ANALYSIS

Arsenic is toxic to humans with the lethal dose being approximately 1 mg/kg/day. At much lower long-term exposures, arsenic is hypothesized to increase the risk of certain cancers. We have developed an irradiat ion position for the neutron activation analysis (NAA) of nail specime ns for arsenic, in support of a case-control study involving New Hamps hire residents consuming well water above the EPA Safe Drinking Water Standard of 0.050 ppm. Arsenic is bound to nail keratin through sulfhy dryl groups proportional to intake providing a convenient means of int egrating arsenic intake in population-based studies. Our objective was to develop the necessary facilities and procedures by which relativel y small samples (i.e. 20 to 100 mg) could be accurately analyzed for a rsenic, so that affordable nutritional epidemiology investigations, re quiring large numbers of samples (>1000 in this case), could be undert aken. A high-flux reflector position, with minimal axial variation thr oughout the fuel cycle, suitable for pneumatic-tube irradiations, was characterized by measurement of the neutron flux distribution (thermal and epithermal) within the irradiation capsule over time. Results fro m application of the method to a case-control study of basal and squam ous cell skin cancer will be presented.