Patients and doctors, relying on scary media reports, may be forgoing radiologic imaging such as CT scans, when the real health risk is lack of a diagnosis, not radiation, writes Bobby Scott, Ph.D., in the fall issue of the Journal of American Physicians and Surgeons. Dr. Scott is a scientist emeritus at Lovelace Respiratory Research Institute in Albuquerque, N.M.
Risk predictions are based on models, statistical conclusions from epidemiologic studies, and extrapolations from high-dose exposures. “There are currently no credible epidemiologic studies that document cancer arising directly from radiologic medical studies or procedures involving low radiation doses,” Scott writes.
The three models include: the threshold model (no harm below 100 mGy); the hormesis model (low doses have a protective effect); and the linear no-threshold (LNT) model (all exposures greater than zero have a proportional risk of harm). Despite lack of scientific validation, the LNT model is always used, Scott writes.
Even if the LNT model were correct, epidemiologic studies incorrectly predict excess cancer from low doses because of incorrect use of the model, Scott states. He analyzes two studies in detail: a cohort study predicting excess leukemia from protracted exposure in the nuclear industry, and a case-control study predicting excess breast cancer related to diagnostic imaging for tuberculosis. If corrected for sampling effects and bias, both studies are consistent with no (zero) effect from radiation.
“The appearance of validity in these studies rests on circular reasoning, cherry picking, faulty experimental design, and/or misleading inferences from weak statistical evidence,” he writes.
Arousing public concerns about the potential harm from repeated diagnostic imaging happens to coincide with pressures to reduce imaging to save money, Scott observes.
Overconcern about low-dose radiation has also caused the loss of thousands of lines from Chernobyl, due to abortions, and Fukushima, due to the deaths of chronically stressed fragile evacuees, he concludes.