Comparative investigation on cancer-related factors in Chinese medical X ray workers

This is the comparative study of 2304 paired persons from ii ray workers and the control group in the cohort study 'cancer incidence among medical diagnostic X ray workers in China'. The distribution of most factors associated with cancer risk were equal between two groups. The unequal distribution of some factors such as tea drinking, smoking only existed after 1970 for the employment calendar year or under 40 years of age at 1990. Unbalanced factors were therefore considered to have little effect on the relative risk of cancers found in the cohort study. Abnormal white cell counting could explain the significant leukaemia risk due to the dose-effect relationship between abnormal white cell counting and annual average dose (mGy.y(-1)). Unbalanced distribution of hepatitis and cirrhosis and infection of hepatitis B might have relevance to the significant RR of liver cancer in the cohort study.