HPRT-MUTANT FREQUENCY AND LYMPHOCYTE CHARACTERISTICS OF WORKERS EXPOSED TO IONIZING-RADIATION ON A SPORADIC BASIS - A COMPARISON OF 2 EXPOSURE INDICATORS, JOB TITLE AND DOSE

Using the clonal HPRT-mutant frequency assay, mutant frequencies 'of h umans have been shown to rise following exposure to large doses of mut agens during radio therapy, chemotherapy or after an atom bomb explosi on. Success in relating mutant frequencies to exposure to high levels of mutagens has encouraged researchers to examine the effects of lower doses, such as those found among workers exposed at their jobs. In or der to relate low doses of mutagens to biological effects, accurate ch aracterization of exposure is critical, but most occupational studies are forced to use gross measures of exposure derived from job title or professional judgments as to potential exposure. Mutant frequencies a nd other relevant lymphocyte characteristics of 58 industrial workers were related to exposure status in two ways. When workers were classed as ''exposed'' or ''unexposed'' to ionizing radiation, no difference in any biological variable was seen between the two groups. When dosim eter readings were used as the exposure indicator, significant relatio nships appeared between dose and mutant frequency and CD4/CD8 lymphocy te subpopulation ratios. Mutant frequency was also positively related to age and smoking status. The time course of exposure and of appearan ce of mutant cells is discussed, and it is suggested that this relatio nship receive attention in occupational studies of genotoxic effects.