Hepatic function in previously exposed thorium refinery workers as compared to normal controls from the health and nutrition survey.

The effect of thorium exposure on hepatic function was investigated in 275 former workers of a thorium refinery. Body burden of radioactivity from the decay chain of thorium was measured as 212Bi and 220Rn in the exhaled breath. Asparate aminotransferase, globulin and total bilirubin in sera were found to be associated with body burden of radioactivity at high levels of significance. Thorium-exposed workers were also compared with a population of white males from the Health and Nutrition Survey conducted by the National Center for Health Statistics from 1971 to 1975. The results showed the means of aspartate aminotransferase alkaline phosphatase to be significantly higher (P = 0.0001) in the thorium-exposed workers when corrected for age, alcohol use and weight. The changes observed in liver function may be compatible with a toxic effect of thorium or daughter products on hepatocytes. The correlation of some hepatic function tests with body burden of radioactivity suggests a radiation effect of thorium although a chemical toxic effect cannot be ruled out and further investigation of chemical toxicity of rare earths are indicated.