Analysis of solid cancer incidence risk among the population exposed in the East Urals Radioactive Trace over 1957–2009

Objective: Assessment of solid cancer incidence risk in the Chelyabinsk subcohort of the East Urals Radioactive Trace over the 53-year period of follow-up with use of the individualized doses accumulated in the soft tissues calculated on the basis of the new dosimetric system TRDS-2016. Materials and methods: The thermal explosion of the storage tank of the «Mayak» production Association radioactive waste in September, 1957 led to the formation of the East Urals Radioactive Trace and radiation exposure of the population living on the territory of the trace. Members of the created cohort received chronic external and internal radiation exposure. The mean dose to the soft tissues over the entire follow-up period amounted to 30 mGy, maximum – 960 mGy. The number of the study cohort is 21 394 persons. Over 53 years (from 1957 to 2009) 1426 cases of solid cancer excluding 73 hemoblastoses and 101 cases of non-melanoma skin cancer are registered in the cohort on the catchment area. Person-years at risk amount to 437 719. Individualized doses for the cohort members were evaluated on the basis of the improved dosimetric system developed by the specialists of the Urals Research Center for Radiation Medicine. The analysis was carried out by means of the Poisson regression method with the use of the software AMFIT. Confidence intervals were calculated using the maximum likelihood estimation. Results: Risk analysis of solid cancer incidence in Chelyabinsk subcohort of the East Urals Radioactive Trace has been carried out for the first time. A significant increase in solid cancer incidence risk with increasing the dose was obtained for the cohort members who were followed-up for 53 years. The excess relative risk per dose is 0.049/100mGy (90% of DI: 0.003; 0.010) according to the linear model. No significant effect modification of the excess relative risk value due to non-radiation factors was revealed. The results of the study demonstrate that the value of excess relative risk of solid cancer incidence per unit dose after chronic exposure at low or moderate doses can be compared to that at high doses.