Internal exposure to alpha particles emitted by radionuclides (particularly plutonium and uranium) is associated with an increased risk of lung cancer mortality, according to a study led by ISGlobal, Barcelona. The results, published in Epidemiology, are consistent with estimates of risk from other types of radiation and compatible with current Radiation Protection recommendations.
Knowledge of the long-term health effects of ionizing radiation (i.e. radiation with enough energy to break chemical bonds such as those in DNA molecules) derives mainly from populations exposed to gamma and X-rays, particularly Japanese atomic bomb survivors, and populations receiving external doses due to occupational, medical and environmental exposures. However, very little is known about the long-term effects of low level internal exposure to alpha particles. In contrast with neutrons, gamma or X-rays, alpha particles only travel a few centimetres in air and are unable to penetrate the skin. However, they can cause serious cellular damage if ingested or inhaled.
The goal of the study was to estimate the risk of lung cancer in populations exposed to low doses of alpha particles through inhalation. The authors conducted a case-control study of lung cancer mortality among Belgian, French and UK cohorts of uranium and plutonium workers, for which they determined individual lung doses from alpha-emitters.
Most subjects in the study had low doses from uranium and/or plutonium. However, a dose-related increase risk of lung cancer was still observed. “This study is the first in which individual estimates of dose have been reconstructed to estimate the risk of lung cancer mortality among European nuclear workers exposed to these radionuclides” says Elisabeth Cardis, head of the Radiation Programme at ISGlobal and coordinator of the study.
The radiation risk estimates in this study are similar to those previously reported in studies of higher dose plutonium workers and of uranium miners exposed to radon. However, James Grellier, lead author of the paper, points out that uncertainties remain (concerning individual dose reconstruction and lack of additional information on tumour location, type or histology) and that these findings cannot be considered as definitive.
Grellier J, Atkinson W, Bérard P, et al. Risk of lung cancer mortality in nuclear workers from internal exposure to alpha particle-emitting radionuclides. Epidemiology. 2017 May 17.