Renal thorium and uranium excretion in non-exposed subjects: influence of age and gender

The excretion of 238U and 232Th was investigated by ICP-MS in a group of 30 males (mean age 41 ± 18 years, range 7 to 73 years) and 33 females (43 ± 21 years, 11 to 84 years). For the thorium excretion, the geometric mean is 34 μBq/day (SD 1.90) for the whole group, 40 μBq/day (SD 2.01) for the males and 30 μBq/day (SD 1.78) for the females. The difference between the males and females is statistically insignificant. A certain increase in the excretion was observed with increasing age but the correlation coefficient of the linear relationship is statistically insignificant. For uranium, the geometric means (SD) for the whole group, the male subgroup, and the female subgroup, in μBq/day, are 237 (2.50), 287 (2.09), and 200 (2.81). The difference between the two subgroups is statistically insignificant. The excretion increases slightly with age; the correlation coefficient of the linear relationship is statistically significant. The day-to-day fluctuations in the excretion of both Th and U are considerable. (P.A.)