Levels of 234U, 238U and 230Th in excreta of uranium mill crushermen

Pacific Northwest Laboratory conducted a research program to measure uranium and thorium levels in excreta of uranium mill crushermen who are routinely exposed to airborne uranium ore dust. The purpose of this work was to determine whether 230Th was preferentially retained in the body over either 234U or 238U. Urine and fecal samples were obtained from 14 active crushermen with long histories of exposure to uranium ore dust, plus four retired crushermen and three control individuals for comparison. Radiochemical procedures were used to separate out the uranium and thorium fractions which were then electroplated on stainless steel discs and assayed by alpha spectrometry. Significantly greater activity levels of 234U and 238U were measured in both urine and fecal samples obtained from uranium mill crushermen, indicating that uranium in the inhaled ore dust was cleared from the body with a shorter biological half-time than the daughter product 230Th. The measurements also indicated that uranium and thorium separate in vivo and have distinctly different metabolic pathways and transfer rates in the body.