Cancer incidence among Bulgarian medical radiation workers: epidemiological study.

PURPOSE: To look for the cancer incidence in a cohort of medical radiation workers in relation to work history (year of first employment, duration of occupational exposure, and radiation doses received for the whole period). MATERIALS AND METHODS: In this retrospective study the cancer incidence among 315 medical workers (radiotherapists, diagnostic radiologists and technical personnel) was compared with that of 320 other medical specialists not having occupational contacts with radiation sources, who worked in hospitals in the territory in Sofia for the period 1960-2000. Data concerning incident cancer occurrence were obtained via a questionnaire. Data for individual doses were extracted from the National System of Individual Dosimetric Control. Descriptive statistics, x(2) test, Fisher's exact test and ANOVA analysis were used. RESULTS: Cancer was more frequently diagnosed among radiation workers compared to other medical specialists (p=0.018). When analyzing by cancer type breast cancer was more frequently diagnosed in radiation workers (p=0.037). No significant relation was observed between cumulative radiation dose and cancer incidence (p=0.12), or cancer incidence by different cancer localizations (p=0.13). Similarly, no difference was found between year of first employment and cancer development in cases and controls (p=0.854 and p=0.178, respectively). Longer whole working period was significantly connected with lower cancer incidence in cases (p=0.015 and p=0.062 for cases and controls, respectively). CONCLUSION: The present study shows that cumulative dose and the duration of work in an ionizing radiation environment does not substantially influence cancer development. Although we found higher cancer occurrence among cases compared to controls, those two factors do not give us ground to confirm that working in an ionizing radiation environment increases cancer incidence. It is important to continue the monitoring of the health status of medical radiation workers.

Radiation exposure to the population of Europe following the Chernobyl accident.

On the occasion of the 20th anniversary of the Chernobyl accident an attempt has been made to evaluate the impact of the Chernobyl accident on the global burden of human cancer in Europe. This required the estimation of radiation doses in each of the 40 European countries. Dose estimation was based on the analysis and compilation of data either published in the scientific literature or provided by local experts. Considerable variability has been observed in exposure levels among the European populations. The average individual doses to the thyroid from the intake of (131)I for children aged 1 y were found to vary from approximately 0.01 mGy in Portugal up to 750 mGy in Gomel Oblast (Belarus). Thyroid doses to adults were consistently lower than the doses received by young children. The average individual effective doses from external exposure and ingestion of long-lived radiocaesium accrued in the period 1986-2005 varied from approximately 0 in Portugal to approximately 10 mSv in Gomel Oblast (Belarus) and Bryansk Oblast (Russia). The uncertainties in the dose estimates were subjectively estimated on the basis of the availability and reliability of the radiation data that were used for dose reconstruction in each country.

Cancer in populations living in regions with radioecological problems in Bulgaria.

PURPOSE: To analyse the incidence and mortality of some malignant diseases among the population living in regions of past uranium extraction in Bulgaria. MATERIAL AND METHODS: A retrospective study on cancer incidence and mortality in the population living around two regions with radioecological problems was conducted. According to the expected individual annual effective doses for the population, regions with expected highest radiation risk (average effective dose > 10 mSv per year) were the villages Yana, Eleshnitza and Seslavtzi (group A), and with expected relatively high radiation risk (average effective dose > 5 mSv per year) were the town of Buhovo, and the villages Dolni Bogrov and Gorni Bogrov (group B). The ecologically clean village German was chosen as a control settlement. The incidence and mortality of gastrointestinal tract cancers, bronchus and lung cancer, breast cancer, thyroid cancer, and myeloid leukaemia for the period 1995- 2001 were studied. RESULTS: The incidence of the gastrointestinal tract cancers in the population of German was significantly lower than those for Bulgaria and for group B. The mortality from this disease of groups A, B and Bulgaria were significantly higher than in the control settlement. Standardized mortality of lung cancer in the population of the villages with highest and relatively high radiation risk was significantly higher than in German and Bulgaria. CONCLUSION: The incidence and mortality changes of diseases studied are a consequence of the impact of many factors. Moreover, they do not characterize the impact of the radiation factor.