This paper presents the results of analyses of the incidence of
malignant neoplasms in lung, liver, and bone and associated connective tissues among Mayak nuclear workers exposed to both internally incorporated
plutonium and to external gamma radiation. The study cohort included 22,373 individuals employed at the reactors and radiochemical and
plutonium production facilities of the Mayak nuclear complex during 1948-1982 and followed up to the end of 2004. All analyses were carried out by Poisson regression, and the doses used were derived using a recently available update of organ doses, Mayak doses-2008. There was clear evidence for the linear association between internal
plutonium dose and the risk of
lung cancer. For males, there was evidence of a significant internal
plutonium dose response for all histological types of
lung cancer evaluated (
adenocarcinoma, squamous-cell, and other epithelial); the estimated excess relative risk (ERR)/Gy for
adenocarcinoma was the largest (ERR/Gy = 32.5; 95% CI: 16.3; 71.9), about 11-fold higher than that for squamous-cell
lung cancer (ERR/Gy = 3.1; 95% CI: 0.3; 9.1). The relationship between
liver cancer risk and
plutonium exposure was best described by a linear-quadratic (LQ) function, but the LQ effect was diminished after restricting internal doses <2 Gy.
Hepatocellular cancer was the most frequently observed type of
liver cancer associated with internal
plutonium exposure, and
hemangiosarcomas were exclusively observed only at high internal
plutonium doses (>4 Gy). For
malignant neoplasms of bone and associated connective tissues, the trend was not statistically significant in relation to internal
plutonium dose, but a statistically significantly higher risk (RR=13.7; 95% CI= 3.0; 58.5) was found among unmonitored female
plutonium workers who were employed in the most hazardous
plutonium production facility commissioned prior to 1950.