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WILLIAM TUCKER: Low-Level Radiation: Is There a Hormetic Effect?

Low-Level Radiation: Is There a Hormetic Effect?

By William Tucker

In the early 1980s, a Taiwan steel company accidentally mixed a quantity of highly radioactive cobalt-60 into a batch of steel rebar.  The radioactive rods were then in the construction of 1,700 apartments.  As a result, people living in these buildings were subject to radiation up to 30 times the normal amount received from the natural background.  

When dismayed Taiwanese officials discovered this enormous error fifteen years later, they surveyed past and present apartment dwellers expecting to find an epidemic of cancer.  Normal incidence would have predicted 160 cancers among the 10,000 residents.  To their astonishment, the researchers discovered only five cases of cancer – a 97 percent reduction from the anticipated amount. Birth defects were also 94 percent below the anticipated rate.  

These findings were published in the Journal of American Physicians and Surgeons in 2004.  As one researcher phrased it, exposure to high levels of background radiation had apparently bestowed upon residents “an effective immunity from cancer.”  [W.L. Chen et al., “Is Chronic Radiation an Effective Prophylaxis Against Cancer?” Journal of American Physicians and Surgeons, Spring 2004.  The upper line is the expected rate of cancer over a 20-year period among 10,000 residents.  The bottom line is the actual rate.]

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The Taiwan apartment incident is just one of many examples that has convinced a wide cohort of radiation scientists that the dangers of low-level exposures have been wildly exaggerated and there may actually be a “hormetic” effect – a word that still doesn’t appear in most dictionaries – meaning that low-level exposure may actually be beneficial.

The whole thing makes a certain amount of sense.  First, there is ample evidence that the body has repair mechanisms that respond almost immediately in repairing genetic damage caused by radiation.  Last December, researchers at Berkeley observed the repair mechanism at work in human breast cells and even managed to film it.  “Our data show that at lower doses of ionizing radiation, DNA repair mechanisms work much better than at higher doses,” said Mina Bissell, a world-renowned breast cancer researcher with Berkeley Lab’s Life Sciences Division. “This non-linear DNA damage response casts doubt on the general assumption that any amount of ionizing radiation is harmful and additive.”  

As a press report in Berkeley’s R&D magazine later expressed it: “This contradicts the standard model for predicting biological damage from ionizing radiation—the linear-no-threshold hypothesis or LNT—which holds that risk is directly proportional to dose at all levels of irradiation,”. 

In April researchers at MIT reported they had exposed mice to 400 times natural background radiation over a period of five weeks without detecting any genetic damage.  ''Almost all radiation studies are done with one quick hit of radiation. That would cause a totally different biological outcome compared to long-term conditions,'' reported Bevin Engelward, an associate professor of biological engineering at MIT and one of the paper’s authors. “Exposure to low-dose-rate radiation is natural, and some people may even say essential for life,” added co-author Jacquelyn Yanch, a senior lecturer in MIT's department of nuclear science and engineering. “The question is, how high does the rate need to get before we need to worry about ill effects on our health?”

All this is quite contradictory to the opinions expressed in the recent special issue of the Bulletin of Atomic Scientists, where the authors not only claim that there is “no safe dose” of radiation but argue that exposure must be measured cumulatively over a period of decades.  When this approach is taken, natural background and medical exposures quickly add up so that after 40 years every American is now approaching the danger zone of 10 rems, above which cancer incidence begins to show up.  As host editor Jan Beyea, former energy director at the Audubon Society, put it:

In developed countries, the average accumulated dose for medical procedures is now so high that a significant percentage of the population in these countries will be above 0.1Sv [10 rem].  Therefore this population will be primed for radiation-induced cancers from release from nuclear reactors or dirty bombs, even using the hypothetical dose-response models of the LNT dissenters.  There is no longer a convenient excuse for avoid using the LNT to estimate consequences from real or projected releases of radioactivity materials, even when the dose of concern is below 0.1 Sv. 

The implications of this debate are enormous.  If in fact there is no danger from radiation at the level of 400 times background – 120 rems spread out over the course of a year – then the entire Fukushima evacuation zone becomes habitable.  The “Land of Wolves” surrounding Chernobyl – which is now thriving with animal life – could be fit for human habitation again as well.  

In fact, as hormesis supporters point out, life on earth evolved in an environment that was much more intensely radioactive than it is today.  It would be surprising if we had not developed mechanisms to deal with routine radiation damage, even though they may have atrophied to some degree.  As Manhattan Project veteran Ted Rockwell expressed it: “If radiation really posed a serious danger to living creatures, we would have developed sensory organs to detect it a long, long time ago.”

Re-evaluating the presumed dangers of low-level radiation may be one of those paradigm shifts that takes the scientific community a generation to absorb.  A whole worldview – and an entire industry – is now dedicated to the premise that radiation is an invisible killer against which huge resources must be deployed – even entire technologies abandoned – in order to provide ourselves with adequate protection.    

Change will only come slowly.  It won’t happen overnight.  

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