During the past two days, I’ve spent 20-30 hours listening to and participating in a sometimes heated and often polite discussion about the health effects of low dose radiation and the rules established or needed to ensure adequate protection.
It’s part of a controversy that has deep roots and stubbornly entrenched sides with a much larger universe of uncommitted or not yet interested observers.
The two entrenched sides are clearly divided between those who support the established radiation protection model known as linear, no-threshold (LNT) and those who oppose the continued use of that model as the basis for radiation protection standards and public communications efforts.
I may be overly optimistic, but it appears that there may be some opportunity for agreements that could end the 62 year-old war.
Before I go much futher, I should admit my bias and confess that I am no longer uncommitted. In fact, I made a choice in 1995 to join the rebel side struggling to change the status quo.
If I was attempting to earn a living as a journalist or as a reporter, I would have to recuse myself and stop writing on the topic.
But I’m not a reporter.
Basis for agreement?
Near the end of the second day of discussions at the joint ANS/HPS meeting titled “Applicability of Radiation Protection Models to Low Dose Protection Standards” an informal straw poll was taken that revealed a possible basis for agreement among the gathered subject matter experts.
We were asked, “Suppose you received a knock on your door in the middle of the night and were greeted by a government official. That official told you it was time to evacuate to avoid a radiation emergency. How high would the level need to be to stimulate you to leave your home?”
Not a single person would leave to avoid 1 mSv/yr, the current radiation protection standard for doses to the general public. No one would leave to avoid 20 mSv/yr, the current internationally accepted (minus the US and a few other holdouts) radiation protection standard for occupational exposure to radiation.
No one would leave to avoid 50 mSv/yr, the occupational standard in the US.
One or two out of the nearly 200 attendees indicated they might leave to avoid 100 mSv/yr. There are reliable studies indicating that the potential delayed cancer risk for a person receiving an acute dose of 100 mSv is statistically different from zero, though at that level the incremental risk to an individual is less than 1%.
Note: That means that a US resident who has a 40% chance of developing cancer during their life would have something less than a 41% chance of developing cancer after the exposure.
If the hypothetical government official indicated that the projected dose over the next year would be 200 mSv, the number of people who said they would leave rose to perhaps 8-10 out of 200. At that point, the unofficial poll devolved into a humorous discussion about how the departure decision would be significantly influenced by the answer to the question “Where would I go?”
Most indicated agreement with laughter when someone suggested they’d leave earlier if offered temporary accommodations at a fancy Las Vegas hotel. Others said that it would require much higher projected doses before they would agree to leave everything they owned if the destination was an evacuation center supplied with bare necessities.
There was nothing official about the poll. All of the reported choices were made with a show of hands. There was no attempt at accountability that would identify someone who might be contradicting an official policy.
The result, however, demonstrated that a diverse group of 200 professionals with expertise in various aspects of the health effects of radiation do not fear exposure to 100 mSv/yr enough to take the currently recommended protective action of evacuation.
Even at a dose that is 100 times higher than the current annual standard (1 mSv) for public exposure and 2500 times higher than the Hanford cleanup standard (0.04 mSv) set for radioactivity in ground water that might reach the Columbia River, 99% of the experts polled would remain in place.
It’s worth noting that the recently updated Protective Action Guide issued by the EPA in 2017 after a prolonged review tells responsible public officials to relocate the public in the intermediate phase of a radiation response event if the projected first year dose exceeds 20 mSv with years 2 and 3 exceeding 5 mSv.
According to the footnotes of the relevant table (Table 1-1 pg 6), evacuation efforts should begin if the projected doses exceed 10 mSv. Immediate evacuation isn’t the same as relocation; relocation is a long term action lasting months to several years.
Description of the current sides in the battle about LNT (no safe dose)
Though the poll described above indicates that both sides in the radiation protection battle personally believe that 100 mSv/yr is safe enough to continue living with it, their officially dug in positions are more sharply divided.
One side is the establishment that accepts the LNT, with its “no safe dose” corollary, as the best available model for radiation protection standards. Most of the radiation professionals that are members of this side are radiation epidemiologists that lean heavily on the reported conclusions of statistical studies involving accidental exposures to relatively large numbers of human beings.
Traditional respect for the potential negative effects of radiation exposure since 1934 has limited the number of available study groups. As one of the epidemiologists who spoke during the past two days described it, his profession leans on taking advantage of information made available by human misfortune.
The study population that is held up as the gold standard is the group of roughly 95,000 people that were present in Hiroshima or Nagasaki when those Japanese cities were destroyed by atomic weapons in August 1945. (There are a few especially unlucky people who were present for both bombings.)
Other available groups include residents of the closed, former Soviet city of Mayak and people exposed to radioactive isotopes as a result of living near or drinking from the Techa River in Russia.
Statistical studies have also been conducted with smaller, less exposed populations of people who received one of several different medical treatments involving radiation, residents of a few specific geographic locations where there is especially high natural background radiation and a group of Taiwanese residents who occupied apartments in buildings containing steel that was found to be contaminated with Co-60.
The pro-LNT side also includes strong representation from bureaucrats, regulators and health physicists who are tasked with official responsibility for radiation protection.
The other side of the discussion includes radiation biologists, radiologists, radiation oncologists, nuclear engineers specializing in radiation, and health physicists. This group of professionals, which is occasionally described incorrectly as “scientific outliers”, generally lean on evidence from experiments involving various animal or tissue models exposed to carefully measured doses of specific types of radiation at specifically chosen dose rates.
They also point to indications from a large body of studies involving relatively small groups of humans that received radiation exposures as a result of accidents, occupational exposure, medical imaging, or medical treatments. Though the statistical power of these studies is often limited by the small numbers of subjects, the anti-LNT group points out that the documented responses do not support the assertion that all radiation doses are harmful.
In fact, many of the professionals believe that the preponderance of the evidence shows that radiation at low to moderate doses and doses that are delivered at low to moderate dose rates have a moderately positive effect on human health. They put low dose radiation in the same longevity and health enhancing category as eating a balanced diet or moderate, regular exercise programs.
This side also includes a fair share of bureaucrats and regulators who recognize that the no safe dose assumption has perhaps outlived its usefulness, especially in light of tragic examples indicating that strict adherence to the status quo can result in situations that harm rather than protect public health.
One deeply experienced radiation health specialist told a moving story yesterday about his transition from being a compliant LNT supporter to being opposed to its continued use as the basis for regulations and decisions. He was in charge of a cleanup at a Pacific atoll that was contaminated to a level at which a population of 1000 living on the island for 30 years might experience one extra cancer death.
He told us how he had to bring six members of his cleanup crew home in body bags because they had been killed in the kinds of accidents that are common in heavy construction and earthmoving operations. The cleanup also resulted in approximately 54 lost time accidents. He said he “hated the LNT” because of the way it transferred risk from hypothetical, computed harms to real harm to real people.
A second commonly used example of unintended consequences of our current application of “no safe dose” is the forced evacuation and subsequent long term relocation of Fukushima area residents. Somewhere between 1500 and 2000 real deaths have been attributed to the evacuation and the effects of relocation; estimates from responsible radiation protection organizations estimate that even using the risk coefficients associated with the currently accepted model, there is only a tiny chance that any individual would have developed an accident-related cancer.
Though the poll described above gives some reason to believe that an agreement may be achievable, the two sides seem stubbornly firm in their current positions. There are leaders on the pro-LNT side who believe that only direct, incontrovertible evidence should result in a change that would be perceived as reducing public safety.
There are also leaders on the anti-LNT side who believe there is plenty of evidence available now to support prompt elimination of the model.
The pro-LNT side answers that confidence with doubts about the strength of the evidence and a challenge to the opposition to provide a more acceptable model before any change can be made. They claim that there is still too much uncertainty to move away from a precautionary approach that assumes there is a risk, even in dose ranges where it cannot be statistically separated from zero.
Today, the meeting agenda includes additional presentations and talks followed by two unstructured panel discussions. One will attempt to identify requirements that must be met before updating regulations and one will attempt to produce some kind of outcome and path forward.
Perhaps coincidentally, at about the same time that those panel discussions occur, there will be a related hearing held by the Senate Committee on Environment and Public Works Subcommittee on Superfund, Waste Management, and Regulatory Oversight.
That hearing, titled “Oversight of the Environmental Protection Agency’s Implementation of Sound and Transparent Science in Regulation” isn’t limited to radiation protection, but advance coverage of the hearing indicates that might be one of the more contentious topics discussed by the witnesses.