Cancer mortality after low dose exposure to ionising radiation in workers in France, the United Kingdom, and the United States (INWORKS): cohort study

A new article by researchers from the International Agency for Research on Cancer (IARC) and partner institutions in France, Spain, the United Kingdom, and the USA finds that workers in nuclear facilities who are persistently exposed to low doses of ionizing radiation experience an increase in deaths due to cancer.

These results are particularly important because the public’s exposure to ionizing radiation has increased in recent decades, even doubling in some countries, primarily due to increases in medical imaging procedures.

“This major update of cancer risk in a large cohort of nuclear workers who were exposed to ionizing radiation provides additional evidence to strengthen radiation protection measures for workers and the general public,” says Dr Mary Schubauer-Berigan, Acting Head of the Evidence Synthesis and Classification Branch at IARC. “Protection against harmful effects of exposure to ionizing radiation is of primary interest as its use becomes more widespread in contemporary medical and occupational settings.”

“We wanted to strengthen the scientific basis for radiation protection by directly studying workers in settings where low-dose and low-dose-rate radiation exposures occur,” says the article’s corresponding author, Dr David Richardson, a professor of environmental and occupational health at the University of California, Irvine (USA) Program in Public Health.

The researchers found that the mortality rate due to cancer increased by more than 50% per gray (Gy) of low-dose ionizing radiation that nuclear industry workers were exposed to during their employment. A gray is a unit of the radiation quantity absorbed dose that measures the energy deposited by ionizing radiation, defined as the absorption of one joule of radiation energy per kilogram of matter.

This finding of an excess relative rate of mortality from cancer per Gy is larger than estimates that currently inform radiation protection.

The new article marks another milestone in the International Nuclear Workers Study (INWORKS), which has followed up 309 932 workers in the nuclear industry for an average of nearly 35 years, resulting in a total follow-up of 10.7 million person-years. The workers were employed at nuclear sites in France, the United Kingdom, and the USA and were monitored with radiation badges, which measured their exposure to radiation, enabling researchers to examine the associations between radiation dose and mortality due to solid cancers.

The study included 103 553 deaths, of which 28 089 were due to solid cancers. The estimated rate of mortality due to solid cancer increased with cumulative dose by 52% (90% confidence interval, 27% to 77%) per Gy. Restricting the analysis to the low cumulative dose range (0–0.100 Gy) approximately doubled the estimate of association per Gy, as did restricting the analysis to workers hired in the more recent years of operations when estimates of occupational external penetrating radiation dose were recorded more accurately. It is important to note that the average cumulative radiation dose among the workers in the study was much lower, at 0.021 Gy (to the colon).

Increasing the understanding of associations between low-dose and low-dose-rate radiation exposures and cancer is essential to ensure that exposure limits for members of the public and people working with ionizing radiation are adequately protective. These results may also inform decisions about medical uses of ionizing radiation, while it is recognized that the benefits of medical radiation use must also be considered. These new results should help radiation protection organizations, such as the International Commission on Radiological Protection, in their risk assessments in settings where low-dose and low-dose-rate radiation exposures occur.

The INWORKS study partners are IARC, the Institut de Radioprotection et de Sûreté Nucléaire (France), the UK Health Security Agency, the National Institute for Occupational Safety and Health (USA), the Instituto de Salud Global de Barcelona (Spain), and the University of California, Irvine (USA).

Richardson DB, Leuraud K, Laurier D, Gillies M, Haylock R, Kelly-Reif K, et al.
Cancer mortality after low dose exposure to ionising radiation in workers in France, the United Kingdom, and the United States (INWORKS): cohort study
BMJ, Published online 16 August 2023;
https://doi.org/10.1136/bmj-2022-074520