Until now, the notion that has been followed is hat until the impact of low-dose radiation is ascertained, the safest thing to do is to assume the worst.
For Andrew Maidment, the chief of physics for the Department of Radiology at the University of Pennsylvania, it was one of the oddest phone calls he’d ever received. “A woman called me up once,” he remembers, “and I hear this child screaming in the background, yelling and crying, crying. She starts off with, can I hug my son again?”
It was an example of a phenomenon that scientists and other experts have dubbed radiophobia — the fear of ionising radiation. Every horror filmmaker worth her fake blood and monster makeup knows that nothing is more terrifying than the unseen: the creak on the stairs, the shadow on the curtains, the hint of fatal evil.
And radiation — a mysterious presence that can’t be felt by our senses — is just such a terror.
This fear has become the default setting for most people — and plenty of experts argue that’s for good reason. Ionising radiation strips electrons from atoms and molecules, converting them into ions, or charged particles. And in atoms and molecules comprising living tissue, such as DNA, it can wreak havoc. If the intensity and rate of exposure are too great, the organism sickens and can die. This is called acute radiation syndrome, or ARS, and it killed many people in the aftermath of the atomic bombings of the Japanese cities of Hiroshima and Nagasaki in the 1940s. It also took a toll following the nuclear accident at Chernobyl, which was recently revisited, to critical acclaim, in a haunting HBO miniseries. Fortunately, most living organisms rarely, if ever, encounter radiation at such toxic levels.
Crystallising events like these have reinforced in the popular mind a technical model that today informs the regulation of nuclear radiation the world over. It’s called the “LNT” model, short for “linear no-threshold,” and it holds that at any level of radiation exposure greater than zero, there is some damage to human DNA. The higher the level, the greater the harm. The “linear” part of the LNT refers to the shape of a line graph plotting cancer risk against radiation dose: not a curve, but a straight line beginning at zero and proceeding upward to infinity. According to the LNT model, all radiation doses, however small, are dangerous, and the harm is cumulative over time. Thus, any exposure must be held to what nuclear regulators would call an “as low as reasonably achievable” dose, or ALARA.
To most scientists, regulators, and the public at large, this only makes sense. And yet, an increasingly vocal group of nuclear experts suggests that the LNT model and its zero-sum approach to radiation may well be doing more harm than good. Naturally occurring radiation surrounds us all the time, they point out — emanating up from the Earth itself, and raining down on us from the cosmos. And outsized fear of radiation, they say — driven largely by the LNT framing — does much more than frighten people like the mother who queried Maidment. It drives voters and governments, for example, to abandon or avoid nuclear power — even though its fossil-based alternatives pollute the air and warm the planet, arguably killing far more people each year. (Indeed, according to the World Health Organization (WHO), 4.2 million people die every year from outdoor air pollution — orders of magnitude more deaths than those attributable to all civilian nuclear accidents, and the bombings of Nagasaki and Hiroshima, combined.)
Similarly, the partial meltdown of three reactors at Japan’s Fukushima Daiichi Nuclear Power Plant in 2011 led to mass evacuations that many experts now say resulted in more deaths than the earthquake and tsunami that caused the accident. “Overestimating radiation risks using the LNT model may be more detrimental than underestimating them,” argued researchers Jeffry Siegel and James Welsh in a 2015 article in the journal Technology in Cancer Research and Treatment, “as this approach has resulted in unnecessary loss of life due to traumatic forced evacuations, suicides, and unneeded abortions after the Fukushima nuclear accident.”