power plant in Germany
Protracted exposure to ionizing radiation, even at low doses, can increase a person’s risk of dying from certain leukemias, according to research published in The Lancet Haematology.
The study showed that protracted radiation exposure was associated with an excess risk of leukemia mortality, particularly for chronic myeloid leukemia (CML).
However, there was no excess mortality risk for chronic lymphocytic leukemia (CLL).
Investigators also observed an association between ionizing radiation exposure and death from multiple myeloma or lymphoma, but they said the evidence for these associations was not strong.
“To date, this study provides the most precise evaluation of the risk of developing leukemia linked to the protracted low doses of radiation received by nuclear workers throughout their careers,” said study author Ausrele Kesminiene, MD, of the International Agency for Research on Cancer, the specialized cancer agency of the World Health Organization.
“It shows that the nuclear workers we studied have a small increase in the risk of dying from leukemia as their exposure to radiation increases.”
This study, known as INWORKS, included 308,297 workers who were monitored for exposure to radiation.
Subjects were employed for at least 1 year by the Atomic Energy Commission, AREVA Nuclear Cycle, or the National Electricity Company in France or the Departments of Energy and Defense in the US. The study also included nuclear industry employers in the National Registry for Radiation Workers in the UK.
Investigators assessed the risk of death from hematologic malignancies among these subjects. The team used Poisson regression to quantify associations between the estimated radiation dose in the red bone marrow and mortality from malignancy.
The mean follow-up was 27 years, and nearly 22% of workers died during that time. The mean cumulative radiation dose was 16 mGy, the median was 2.1 mGy, and the mean yearly dose was 1.1 mGy.
Quantifying the risk
The investigators found “strong evidence” for a positive association between exposure to ionizing radiation and the risk of death from leukemias, excluding CLL. Specifically, the excess relative risk of mortality per Gy of radiation was 2.96 (90% CI 1.17-5.21).
Even low doses of radiation posed a risk. Fifty-three percent of deaths from leukemia (excluding CLL) occurred in workers who had accrued less than 5 mGy of radiation.
However, the relative risk of death from leukemia (excluding CLL) increased with the radiation dose. The relative risk was 1.00 for 0-5 mGy, 1.01 for 5-50 mGy, 1.30 for 50-100 mGy, 1.19 for 100-200 mGy, 2.30 for 200-300 mGy, and 1.70 for more than 300 mGy.
The data also showed the risk of cancer mortality associated with radiation exposure varied according to the type of leukemia.
The excess relative risk of mortality was 10.45 for CML, 1.29 for acute myeloid leukemia, and 5.80 for acute lymphoblastic leukemia. For CLL, the excess relative risk was -1.06.
The investigators also found positive associations between radiation exposure and mortality from Hodgkin lymphoma, non-Hodgkin lymphoma, and multiple myeloma. However, the findings were “highly imprecise,” with confidence intervals that spanned 0.
