Characterization of tritium exposures by measuring tritiated metabolites in urine

A high-performance liquid chromatography (HPLC)-based method was developed to look for the presence of characteristic urinary metabolites associated with different tritium-exposure situations. Non-volatile metabolites in urine were isolated by evaporating an aliquot of urine samples, at room temperature under nitrogen, from animals percutaneously exposed to tritiated thymidine, tritiated formaldehyde, tritium-gas-contaminated metal surfaces and tritiated pump oil. A total of 40 fractions were collected at 1 min intervals with a flow rate of 1 ml x min-1, and their tritium activities were measured. The activity profile of tritium showed that the ratios of non-volatile tritiated metabolites in fraction I (0-20 min) to fraction II (20-40 min) were noticeably different among the animals exposed to tritiated thymidine (77.2±4.5), tritiated formaldehyde (40.9±3.3), tritium-gas-contaminated metal surfaces (16.5±2.5), or tritiated pump oil (8.7±0.4) 24 h post-exposure. Our results suggest that, if the nature of a tritium exposure is unknown, comparison of the ratio of fraction I to fraction II in non-volatile tritiated metabolites may be useful in characterizing the source and the nature of tritium exposure. (author)