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This is the first analysis of solid cancer incidence in the Techa River cohort, a general population of men and women of all ages who received chronic low-dose rate exposures from environmental radiation releases associated with the Soviet nuclear weapons programme. This cohort provides one of the few opportunities to evaluate long-term human health risks from low-dose radiation exposures.Cancer incidence rates in this cohort were analysed using excess relative risk (ERR) models. The analyses make use of individualized dose estimates that take into account residence history, age and other factors. Cases are identified on the basis of continuing, active follow-up of mortality and cancer incidence.Based on 1836 solid cancer cases with 446 588 person years accrued over 47 years of follow-up, solid cancer incidence rates were found to increase with dose and about 3% of the cases were attributable to radiation exposure. The ERR was 1.0/Gy (P = 0.004 95% CI (0.3; 1.9) in a linear dose-response model. There was no significant non-linearity in the dose response and no indication of effect modification by gender, ethnicity, attained age or age at first exposure.The Techa River cohort provides strong evidence that low-dose, low-dose rate exposures lead to significant increases in solid cancer risks that appear to be linear in dose. The results do not suggest that risks associated with low-dose rate exposures are less than those seen following acute exposures such as were received by atomic bomb survivors.

Large quantities of radioactive materials released over time from the Mayak nuclear weapons facility caused significant internal and external exposure for people living along the banks of the Techa River (Southern Urals, Russia). We conducted a nested case-control study in the Extended Techa River Cohort to determine whether the risk of leukaemia incidence increased with protracted exposure to ionising radiation or with other non-radiation risk factors. The study included 83 cases identified over 47 years of follow-up and 415 controls matched for sex, age at diagnosis, age (within a 5 year age group), and date of initial residence in the riverside area. External and internal doses have been calculated using the Techa River Dosimetry System 1996 (TRDS96). Conditional logistic regression was used to calculate odds ratios per Gray (OR/Gy) and 95% confidence intervals (95% CI). After excluding cases of chronic lymphoid leukaemia, the OR/Gy of total, external, and internal doses were 4.6 (95% CI: 1.7-12.3), 7.2 (95%CI: 1.7-30.0) and 5.4 (95%CI: 1.1-27.2), respectively. A history of solid tumour, either malignant or benign, before the leukaemia diagnosis was associated with a 2.5-fold increase in the leukaemia risk (95% CI: 1.1-5.9). Even though the analysis of confounders was less useful than expected because of missing data, multivariate analyses that took the exposure dose into account confirmed the association between leukaemia incidence and tumour history.

In the 1950s many thousands of people living in rural villages on the Techa River received protracted internal and external exposures to ionizing radiation from the release of radioactive material from the Mayak plutonium production complex. The Extended Techa River Cohort includes 29,873 people born before 1950 who lived near the river sometime between 1950 and 1960. Vital status and cause of death are known for most cohort members. Individualized dose estimates have been computed using the Techa River Dosimetry System 2000. The analyses provide strong evidence of long-term carcinogenic effects of protracted low-dose-rate exposures; however, the risk estimates must be interpreted with caution because of uncertainties in the dose estimates. We provide preliminary radiation risk estimates for cancer mortality based on 1,842 solid cancer deaths (excluding bone cancer) and 61 deaths from leukemia. The excess relative risk per gray for solid cancer is 0.92 (95% CI 0.2; 1.7), while those for leukemia, including and excluding chronic lymphocytic leukemia, are 4.2 (CI 95% 1.2; 13) and 6.5 (CI 95% 1.8; 24), respectively. It is estimated that about 2.5% of the solid cancer deaths and 63% of the leukemia deaths are associated with the radiation exposure.