On Tuesday, the Associated Press reported that the Trump administration was quietly seeking to roll back the Environmental Protection Agency's regulations on radiation exposure. The story took a closer look at a rule the EPA proposed back in April called "Strengthening Transparency in Regulatory Science." When it was released, most coverage focused on the proposal's potential limitation of what studies the EPA could and could not use in decision-making—it essentially demanded the EPA not use any studies based on data that isn't publicly available.
Ironically, the transparency rule is hiding another agenda. Paragraphs scattered throughout the document make it clear that the proposed rule is meant to re-evaluate the science behind "the dose response data and models that underlie what we are calling 'pivotal regulatory science.'" That jargon means the EPA wants to challenge the assumptions that underlie its current guidelines on toxic exposure.
"The so-called transparency rule is an insidious dodge," said Rush D. Holt, a former congressman and current president of the American Association for the Advancement of Science, before a Senate subcommittee on October 3rd. "It apparently is about reducing regulation." And though the actual rule is vague, comments in the press release and a July update to the EPA guidelines on radiation exposure make it seem that nuclear regulation is on the chopping block.
Currently, the nuclear industry, the EPA, and other groups operate on the assumption that there is no safe dose of radiation, no matter how small. This is based on the "linear no-threshold" model (LNT). The LNT model is based on studies of people exposed to high and medium doses of radiation, including survivors of Hiroshima, Chernobyl, and Fukushima. That data shows that the higher the dose of radiation you receive, the more severe the consequences—in other words, that the response to doses is linear. The more radiation, the more health effects.
Because it's much harder to accurately measure small doses of radiation in large populations over long periods of time, there isn't much data available on the lower end. Still, most scientists agree that the relationship stays the same for small amounts of ionizing radiation: Small doses increase the aggregate risk of cancer by a relatedly small amount. LNT's prevalence pushes regulatory agencies, professional associations, and medical fields to keep radiation doses "as low as reasonably achievable" in all people, especially considering some groups (children, especially) are more vulnerable to radiation than others.
There's no controversy about the effects of mid- to high-level doses of radiation: They're harmful, and we've seen this in survivors of radiation exposure for decades. But there's a fair amount of quibbling at the lower end. Despite the wide international acceptance of LNT, some scientists claim that a little radiation actually isn't that bad for us—that there's a "non-linear dose response." Some of the dissenters argue that there's a threshold dose for negative effects—that below, say, 50 mSv (millisieverts, the unit used to measure radiation dose in the body), there's no harm done. (For context, typical radiological exams, like X-rays or CT scans, produce between three and 30 mSv.) And the proposed EPA rule centers around these non-linear claims, citing "growing empirical evidence of non-linearity in the concentration-response function for specific pollutants and health effects."
It’s true that studies have found major flaws in the LNT model. It doesn't help us reliably and consistently understand what low doses do to the human body, and there's also controversy over the differences between acute and lifetime radiation exposure. But in a larger public-health sense, LNT is cautious and prudent. Just because there isn't documented proof of harm at very low doses doesn't mean harm isn't being done, and an inaccurate model means that it's also possible that LNT sometimes underestimates cancer risks from low doses. In the absence of more definitive data, multiple groups and studies—the National Academy of Sciences, the International Commission on Radiological Protection, and more—have recommended holding fast to regulations that keep radiation exposure as low as possible, at least until a new model is robustly tested and accepted.
Others go even further and argue that small doses of radiation are good for you. Edward Calabrese, a professor at the University of Massachusetts, is quoted in the April EPA press release—he was glad the agency was "recognizing the widespread occurrence of non-linear dose responses," and he appeared in the October 3rd Senate hearing on the rule.
Calabrese is a major critic of the LNT model. He is famous for championing "hormesis"—the idea that small amounts of radiation are beneficial, or "hormetic," the way small amounts of vitamins are good for you but large amounts can hurt you. He claims his research shows widespread evidence of hormesis in a number of toxins, and that environmental risk assessment should reorient itself around this dramatic model. Calabrese edits Dose-Response, a peer-reviewed academic journal focused on non-linear toxicology models, and his work has significantly raised the theory's profile.
"Movement away from LNT is badly needed," Calabrese said before the Environment and Public Works subcommittee. He claims LNT was driven by radiation scares from the 1950s, mistakes, misconduct, and more, and it has damaged both public health and the economy.
Although Calabrese focused on more mainstream criticisms of LNT before the Senate, his hormesis work is controversial. In 2010, Kristin Shrader-Frechette used Calabrese's work as a case study of "special-interest science." Shrader-Frechette compares Calabrese and others to the Queen of Hearts in Lewis Carroll's Through the Looking Glass. "Just as the Queen claimed she could believe six impossible things before breakfast, SIS proponents often use scientific concepts/methods in ways that are 'impossible,'" she wrote. She points out that Calabrese's CV shows significant research funding from Atlantic Richfield Oil (ARCO), Dow Chemical, ExxonMobil, Proctor and Gamble, and R.J. Reynolds Tobacco. And despite Calabrese's nearly 20 years of advocacy for the theory, even friendly reviews indicate radiation hormesis needs further scientific support.
The EPA proposal doesn't explicitly state that it will base decisions around hormesis. "The proposed regulation doesn't talk about radiation or any particular chemicals," EPA spokesman John Konkus said on Tuesday. "And as we indicated in our response, EPA's policy is to continue to use the linear-no-threshold model for population-level radiation protection purposes which would not, under the proposed regulation that has not been finalized, trigger any change in that policy."
But the rule promises to give special consideration to studies exploring "various threshold models across the exposure range" and pledges to "evaluate the appropriateness" of using the LNT model. If it's approved, the EPA's accepted scientific standard for acceptable radiation doses could change from "as low as reasonably achievable" to a standard that identifies no effect or positive effects from low doses. That could lead to the repeal of strict regulations on radiation containment, which the EPA might deem unnecessary.
*Update — October 3rd, 2018: This article has been updated to further clarify the EPA's position on radiation exposure guidelines.