Article review date
November 2024
Article publication date
August 2024
Summary
This study reports on the results of two birth cohort studies that were constructed to study the effects of Iodine-131 that was released due to a fire at Windscale nuclear reactors at Sellafield in Cumbria, England in 1957. The study aimed to examine the incidence of thyroid cancer in young children in Cumbria. Iodine-131 concentrates in the Thyroid, hence thyroid cancer was the key outcome of the studies. The two cohorts included 56,086 births in Cumbria between 1950-1959 and 137,444 more births in Cumbria from 1959-1980, respectively. These cohorts were broken up into three groups based on regions that were modelled to have high to low levels of Iodine-131. Area 1 being the highest, Area 2 with intermediate exposure level and Area 3 having the lowest. For the combined results from Areas 1 (highest) and 2 (intermediate) there was no increased risk of thyroid cancer with an Incidence rate ratio (IRR) of 0.68 (95% confidence interval (CI): 0.24-1.56). There were no cases of thyroid cancer for those in the highest exposure group. The authors conclude that a substantially raised thyroid cancer risk, even in the highest exposure groups, can be excluded. The authors said follow-up studies should continue to monitor the exposed groups for thyroid cancer. However, noted that these studies are unlikely to result in any changes to these conclusions.
Published in
Radiation and Environmental Biophysics
Link to study
Commentary by ARPANSA
The study examined the impact of Iodine-131 released due to an accident at a nuclear power plant. It provides strong evidence that the preventative measures instituted after the emergency, such as a restriction on the distribution of contaminated milk, were correct and may have prevented an increased risk of thyroid cancer occurring in the area. This is illustrated by the events in Chernobyl where consuming heavily contaminated milk led to tens of thousands of children receiving thyroid doses > 1 Gy and thousands of additional thyroid cancer cases (UNSCEAR 2018). This study also provides confidence in the conclusions of UNSCEAR 2022 about the impact of the Fukushima Dai-ichi nuclear reactor accident in Japan during in March 2011. UNSCEAR 2022 concluded that increased thyroid cancer risks will be small and unlikely to be detectable. This is because of the protective measures put in place after the accident that limited Iodine-131 exposure. No adverse health effects have been reported for the residents of Fukushima that could be directly attributed to radiation exposure (UNSCEAR 2022).
ARPANSA also undertook protective measures during and after the Fukushima Dai-ichi nuclear reactor accident to ensure the safety of Australians. This included investigating the levels of radioactivity in foods imported into Australia from Japan and testing the levels of radioactivity in the ocean water, seafood and the atmosphere. Other products coming into Australia from Japan were also tested such as cars, and cargo vessels. ARPANSA can use the lessons learnt from these accidents to improve how it responds to nuclear accidents in the future and to ensure the safety of Australians.
