Objective:To study the risk of malignant tumor in medical X-ray workers in Shanghai and provide scientific data for the study on occupationally exposed population.Methods:A retrospective cohort study was conducted to investigate the risk of cancer. Totally, 715 physicians in radiology departments during 1950-1980 in Shanghai were selected as exposure group, while 738 with non-radiology departments in the same hospital in the same time period as control group. The basic information on the selected physicians and associated cancer incidence were collected. The comulative number of individuals with cancer from 1980 to 2021 was calculated. The relative risk ( RR) of cancer was analyzed using logistic regression model in terms of gender, birth year, and work starting year. As well, stratified analysis based on confounding factors was conducted. Results:A total of 1 369 individuals were followed up, including 668 in exposure group and 701 in control group. The cumulative person-year of observed individuals was 52 980. As of 31 December 2021, a total of 199 patients with various malignant tumors were identified. The results of the logistic regression analysis showed that the risk of malignant tumors in exposure group was significantly higher than that in control group. The adjusted RR of solid cancer and total cancer was 1.49 (95% CI: 1.08-2.05, P=0.015) and 1.40 (95% CI: 1.02-1.92, P=0.036), respectively. In addition, the risk of thyroid cancer in exposure group was significantly higher than that in control group ( RR=10.06, 95% CI: 2.05-49.62, P=0.005). Stratified analysis showed that the exposure group had a higher risk of total cancer both for femals and workers taking their jobs at age of 21-25. Conclusions:The risk of thyroid cancer, solid cancer and total cancer in the medical X-ray workers was significantly higher than that in control group. It is suggested that radiation protection in medical practice should be strengthened for the occupationally exposed workers, especially for femals and workers taking their jobs at low age.

Background Individual monitoring of occupational external exposure is an essential part of the occupational health management of radiation workers, and is an important basis for the evaluation of individual absorbed dose and the diagnosis of occupational radiation diseases. Continuous participation of monitoring service providers in intercomparison is a fundamental quality assurance for routine monitoring, which can identify problems and improve them in time. Objective Taking the Laboratory of Radiation Protection in Shanghai Institute of Preventive Medicine as an example, to evaluate the performance of an individual occupational external dose monitoring system in the laboratory, identify influencing factors of the monitoring results, and provide a basis for improving the quality of daily monitoring by analyzing the process and results of a national intercomparison of individual dose monitoring. Methods According to the Testing criteria of personnel dosimetry performance for external exposure (GBZ 207-2016), and the relevant requirements of Class II (photon) inspection, a total of 20 groups of blind sample dosimeters were measured for four consecutive years from 2018 to 2021. The radiation energy source of each group was identified, and related personal dose equivalent H_p(10), the uncertainty of measurement results, and the deviation between the reported value and the reference value were calculated. The national intercomparison process and results of individual dose monitoring were also analyzed. Results The energy sources of the blind samples in the tested laboratory for four years were N100 or Cs-137. The reported dose values of the blind samples were 0.57-4.61 mSv, the combined uncertainties were 0.043-0.365 mSv, the expanded uncertainties (k=2) were 0.09-0.73 mSv, and the relative expanded uncertainties (k=2) were 13.8%-16.4%. The single-group performance ∣P_i∣ of 20 sets of blind samples in the four years was ≤0.10, the yearly comprehensive performance of 5 sets of blind samples was ≤0.10, and the yearly Q score of the test report was >15 points. The laboratory achieved excellent results in the national intercomparison of individual dose monitoring in four consecutive years, except the Q value not reaching full score. Conclusion The laboratory exhibits standardized data processing of individual dose monitoring, generates accurate and reliable results, and meets the requirements of relevant national standards; but it should continue to participate in the national intercomparison of individual dose monitoring, strengthen the angular response research of energy identified dosimeter, improve the monitoring ability of low-dose X-rays, analyze the key points of reducing the uncertainty of measurement results, and continuously improve the monitoring ability.