Time for a fresh look at low-dose radiation

We will never know whether Thomas Aquinas actually pondered this specific question during the Middle Ages, but today the metaphor has shed its religious overtones to be a general warning against engaging in protracted debate on existential issues while more urgent problems fester.

It is also the first thing that comes to my mind when I think of the linear no-threshold (LNT) vs. hormesis debate.

As scientific theories go, LNT has always been weak. It relies on extrapolation from high-dose radiation exposure data, where the effects are clear, to predict the risk of annual doses below 10 rem, where there is simply no epidemiological evidence of increased cancer risk in human populations. However, with the weight of 60 years of government policy and our societal tendency to "err on the side of caution" behind it, dethroning the LNT will always be a formidable task.

Meanwhile, the science of radiation hormesis gets more interesting by the day. Just recently, I learned about the abscopal effect-a well-documented medical phenomenon in which treating a cancerous tumor with radiation creates a systemic immune response in the body that attacks other metastases, even those untouched by radiation. An amazing and medically beneficial effect of radiation! Adherents of hormesis need to be careful about how they communicate, however. Yes, there is a growing body of evidence for the benefits of low-dose radiation exposure, but the idea that "a gamma a day keeps the doctor away" can sound a little . . . well . . . crazy, especially if the pitch includes a conspiracy theory about how the Rockefellers quashed data in the 1950s.

Let's call a truce in the radiation science war. We should all be able to agree that the average person's cancer risk from an added 50-100 mrem of annual radiation exposure is vanishingly small-"not statistically different from zero," in the words of the Health Physics Society-otherwise we would have evacuated Vail, Colorado, a long time ago.

The real crime is how our radiation standards and policies cause us to misallocate public resources on a colossal scale. Each year, roughly 1.7 million Americans will be diagnosed with cancer. Roughly one-quarter of them will experience financial distress because they cannot fully afford prescribed treatment in our current health care system. Yet, the Environmental Protection Agency quietly issued a memo in 2014 that set the Superfund radiation cleanup standard at 12 mrem instead of 15 mrem per year, basically adding $100 billion-roughly $58,000 per new U.S. cancer patient last year-to the estimated cleanup tab for Department of Energy defense sites, with no proof it would save a single life.

Now let's consider the threat of unchecked climate change: thousands, if not millions, of lives lost to extreme heat, violent storms, famine, vector-borne disease, and water-borne illness if we don't bend the emissions curve in the decades to come. That's a worst-case scenario, of course, but can we agree that it's within the realm of plausibility? Can we really allow U.S. nuclear innovation to fail because we are afraid that our waste disposal method might expose someone to a CT scan's worth of radiation 1 million years from now, when presumably cancer will be a thing of the past? There comes a point when intergenerational equity becomes our generation's stupidity.

We don't need to solve the LNT vs. hormesis controversy to prove that our national policies on radiation are flawed. It's time to stop counting angels, fix the problems that are right in front of our face, and start fresh with a public discourse on the issue.-cpiercy@ans.org

(Reprinted with permission from ANS News, July/August 2019, p. 5)