Risk analysis of leukaemia incidence among people living along the Techa River: a nestedcase-control study

Abstract

Large quantities of radioactive materials released over time from the Mayak nuclearweapons facility caused significant internal and external exposure for people living alongthe banks of the Techa River (Southern Urals, Russia). We conducted a nested case-controlstudy in the Extended Techa River Cohort to determine whether the risk of leukaemiaincidence increased with protracted exposure to ionising radiation or with othernon-radiation risk factors. The study included 83 cases identified over 47 yearsof follow-up and 415 controls matched for sex, age at diagnosis, age (within a5 year age group), and date of initial residence in the riverside area. External andinternal 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, theOR/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 orbenign, before the leukaemia diagnosis was associated with a 2.5-fold increase in theleukaemia risk (95% CI: 1.1–5.9). Even though the analysis of confounders was less usefulthan expected because of missing data, multivariate analyses that took the exposure doseinto account confirmed the association between leukaemia incidence and tumourhistory.