The History of the Linear No-Threshold Model and Recommendations for a Path Forward

In dealing with radiation to the population at large, or to populations of radiation workers, the policy of the various regulatory agencies has been to adopt the linear no-threshold (LNT) model to extrapolate from what is known about the excess risk of cancer at moderately high doses and high dose rates, to low doses, including those below natural background.

In our update, we added a citation to a paper by John Cardarelli, Barbara Hamrick, Dan Sowers, and Brett Burk titled “The History of the Linear No-Threshold Model and Recommendations for a Path Forward,” (Health Physics, Volume 124, Pages 131–135, 2022). When I looked over the paper, I found that there is a video series accompanying it. I said to myself: “Brad, that sounds like just the sort of thing readers of your blog might enjoy.” I found all the videos on the Health Physics YouTube station, and I have added links to them below.

Wow! This is not a dry, technical discussion. It is IPMB meets 60 Minutes. This is a hard-hitting investigation into scientific error and even scientific fraud. It’s amazing, fascinating, and staggering.

John Cardarelli, the president of the Health Physics Society when the videos were filmed, acts as the host, introducing and concluding each of the 22 episodes. The heart of the video series is Barbara Hamrick, past president of the Health Physics Society, interviewing Edward Calabrese, a leading toxicologist and a champion of the hormesis model (low doses of radiation are beneficial).

Calabrese claims that our use of the linear no-threshold model is based on “severe scientific, ethical, and policy problems.” He reviews the history of the LNT model, starting with the work of the Nobel Prize winner Hermann Muller on the genetics of fruit flies. He reviews the evidence to support his contention that Muller and other scientists were biased in favor of the LNT model, and sometimes carried that bias to extreme lengths. At first I said to myself “this is interesting, but its all ancient history.” But as the video series progressed, it approached closer and closer to the present, and I began to appreciate how these early studies impact our current safety and regulatory standards.

I watched every minute of this gripping tale. (OK, I admit I watched it at a 2x playback speed, and I skipped Cardarelli’s introductions and conclusions after the first couple videos; there is only so much time in a day.) Anyone interested in the linear no-threshold model needs to watch this. I have to confess, I can offer no independent confirmation of Calabrese’s claims. I’m not a toxicologist, and my closest approach to radiobiology is being a coauthor on IPMB. Still, if Calabrese’s claims are even half true then the LNT assumption is based on weak data, to put it mildly.

Watch these videos. Maybe you’ll agree with them and maybe not, but I bet you’ll enjoy them. You may be surprised and even astounded by them.

Episode 1: Who Is Dr. Edward Calabrese?

Episode 2: LNT Beginnings—Extrapolation From ~100,000,000 x Background?

Episode 3: Muller Creates a Revolution

Episode 4: Muller: How Ambition Affects Science

Episode 5: The Big Challenge

Episode 6: The Birth of the LNT Single-Hit Theory

Episode 7: Pursuit to Be the First to Discover Gene Mutation

Episode 8: “Fly in the Ointment”

Episode 9: Why the First Human Risk Assessment Was Based on Flawed Fruit-Fly Research

Episode 11: Creation of the Biological Effects of Atomic Radiation (BEAR) I Committee

Episode 12: Was There Scientific Misconduct Among the BEAR Genetics Committee Members?

Episode 13: Is Lower Always Better?

Episode 14: Should the Genetics Panel Science Paper Be Retracted?

Episode 15: Follow the Money Trail: “We Are Just All Conspirators Here Together”

Episode 16: The Most Important Paper in Cancer Risk Assessment That Affects Policy in the US

Episode 18: Ideology Trumps Science, Precautionary Principle Saves the LNT

Episode 19: Genetic Repair Acknowledged

Episode 20: BEIR I Acknowledges Repair but Keeps LNT. Why?

Episode 21: BEIR I Mistake Revealed, LNT Challenged, Threshold Supported

Episode 22: Making Sense of History and a Path Forward by Dr. Calabrese