Implications of Assuming a Realistic Intake Regime for Chronic Exposure to Airborne Uranium

In assessing intakes and doses from inhalation exposures, the usual approximation made is that of a continuous constant chronic intake of 24 hours per day, 7 days a week. The effect of assuming a more realistic intake regime of 8 hours per day, 5 days per week, in dose calculations for workers exposed chronically to airborne particulates of uranium has been investigated. Kidney concentrations and urinary excretion rates have been predicted using this more realistic intake regime together with the latest biokinetic models, and the results have been contrasted with similar calculations which assume a constant chronic intake regime. The implications for occupational health are drawn from the results of the work. In particular, it is shown that for estimating kidney concentrations, the simplifying assumption of a constant chronic intake is adequate, but if it is used for estimating dose from measurements of activity in urine, then the dose may be underestimated by up to a factor of three.