In utero exposure to radiation and haematological malignancies: pooled analysis of Southern Urals cohorts

BACKGROUND: It is scientifically uncertain whether in utero exposure to low-dose ionising radiation increases the lifetime risk of haematological malignancies. METHODS: We pooled two cohorts from the Southern Urals comprising offspring of female workers of a large nuclear facility (the Mayak Production Association) and of women living in areas along the Techa River contaminated by nuclear accidents/waste from the same facility, with detailed dosimetry. RESULTS: The combined cohort totalled 19 536 subjects with 700 504 person-years at risk over the period of incidence follow-up, and slightly more over the period of mortality follow-up, yielding 58 incident cases and 36 deaths up to age 61 years. Risk was increased in subjects who received in utero doses of ⩾80 mGy (excess relative risk (ERR): 1.27; 95% confidence interval (CI): −0.20 to 4.71), and the risk increased consistently per 100 mGy of continuous exposure in utero (ERR: 0.77; CI: 0.02 to 2.56). No association was apparent in mortality-based analyses. Results for leukaemia and lymphoma were similar. A very weak positive association was observed between incidence and postnatal exposure. CONCLUSIONS: In summary, the results suggest a positive association between in utero exposure to ionising radiation and risk of haematological malignancies, but the small number of outcomes and inconsistent incidence and mortality findings preclude firm conclusions.