Americium-241 (²⁴¹Am) is the second most significant radiation hazard after ²³⁹Pu at some of the Mayak Production Association facilities. This study summarizes current data on the accumulation, distribution, and excretion of
americium compared with
plutonium in different organs from former Mayak PA workers.
Americium and
plutonium were measured in autopsy and bioassay samples and correlated with the presence or absence of
chronic disease and with
biological transportability of the
aerosols encountered at different workplaces. The relative accumulation of ²⁴¹Am was found to be increasing in the workers over time. This is likely from ²⁴¹Pu that increases with time in reprocessed fuel and from the increased concentrations of ²⁴¹Am and ²⁴¹Pu in inhaled alpha-active
aerosols. While differences were observed in lung retention with exposures to different industrial compounds with different transportabilities (i.e., dioxide and
nitrates), there were no significant differences in lung retention between
americium and
plutonium within each transportability group. In the non-pulmonary organs, the highest ratios of ²⁴¹Am/²⁴¹Am + SPu were observed in the skeleton. The relative ratios of
americium in the skeleton versus liver were significantly greater than for
plutonium. The relative amounts of
americium and
plutonium found in the skeleton compared with the liver were even greater in workers with documented chronic
liver diseases. Excretion rates of ²⁴¹Am in ‘‘healthy’’ workers were estimated using bioassay and autopsy data. The data suggest that impaired liver function leads to reduced hepatic ²⁴¹Am retention, leading to increased ²⁴¹Am excretion.