A new study, recently published in the American Journal of Clinical Oncology, claims the widespread belief that low-dose radiation from X rays, CT scans and other medical imaging increases cancer risk has no empirical evidence to support it and is based on a decades-old, unproved theoretical model.
In the study, the research team re-examined the studies, dating back to over 70 years ago, that led to the adoption of the linear no-threshold (LNT) model, which holds that any dose of radiation increases cancer risk in a linear fashion.
As it turns out, the model is based on studies, mainly conducted in the 1940s, of fruit flies exposed to various amounts of radiation. The alarming results of these trials prompted scientists to conclude that no dose of radiation, no matter how small, can be considered safe.
These findings went unchallenged for the next several decades, until a new study, released in 2009, replicated the previous work, only this time with truly low doses of radiation, and found no evidence for increased carcinogenicity.
This is also in line with empirical work on atomic bomb survivers and other epidemiological trials, which failed to establish any link between small doses of radiation and a raised prevalence of malignant tumours.
Furthermore, for the LNT model to be true, it would have to falsify the established fact that our bodies have evolved to be capable of repairing minor damage inflicted upon us by the low dose radiation that occurs naturally in the environment.
The authors conclude that the LNT model “should finally and decisively be abandoned.”
One caveat worth mentioning, though, is that while the study showed there’s no evidence for low dose radiation increasing the risk of cancer, it did not prove that it doesn’t, which still warrants taking precautionary measures in cases when they’re convenient and inexpensive.
Other than that, however, any claims that medical imaging is hazardous for human health and is therefore best avoided whenever possible “should be vigorously challenged, because it serves to alarm and perhaps harm, rather than educate,” conclude the authors in their paper.