Evaluation of a population with occupational exposure to airborne ammonium perchlorate for possible acute or chronic effects on thyroid function

Employees at an ammonium perchlorate production facility in Nevada and a larger control population from the same chemical complex without direct AP exposure were monitored extensively for airborne perchlorate exposure. Single-shift and working-lifetime cumulative dose estimates were made using standard breathing-rate estimates and assuming rapid absorption, based upon solubility. Calculated single-shift doses ranged from 0.2 to 436 mu g/kg, with an average of 36 mu g/kg. Working-lifetime cumulative doses in the higher exposure group ranged from 8,000 to 88,000 mu g/kg, with an average of 38,000 mu g/kg. Thyroid profiles, including free thyroxine index and thyroid-stimulating hormone level, were obtained both before shift and after shift to assess thyroid-axis perturbation due to single working-shift perchlorate exposure. Thyroid-function data were also analysed with respect to estimates of cumulative exposure to assess any measurable chronic effects on thyroid gland function. Additionally, standard clinical blood test parameters of liver, kidney, and bone marrow function were evaluated to assess any measurable chronic effects of perchlorate exposure on those organs. Multiple regression was used to assess the effects of exposure variables and demographic variables on organ function parameters. No perchlorate-attributable effects on thyroid, bone marrow, kidney, or liver function were detected.