Posted on June 4th, 2009 100 comments
ScienceDaily (Mar. 26, 2008) — Exposure to levels of radon gas typically found in 90 percent of American homes appears to reduce the risk of developing lung cancer by as much as 60 percent, according to a study published in the March issue of the journal Health Physics. The finding differs significantly from the results of previous case-control studies of the effects of low-level radon exposure, which have detected a slightly elevated lung cancer risk (but without statistical significance) or no risk at all.
The study, undertaken jointly by researchers at Worcester Polytechnic Institute (WPI), Fallon Clinic, and Fallon Community Health Plan, is the first to observe a statistically significant hormetic effect of low-level radon exposure. Toxins and other environmental stressors (including radiation) that have a beneficial effect at very low doses are said to exhibit hormesis (scientists believe that the low doses of toxins may stimulate repair mechanisms in cells). Home exposure to radon, a naturally occurring radioactive decay product of radium, has been thought to be the second leading cause of lung cancer, after cigarette smoking. Chemically inert, it can percolate out of the ground into basements.
The study was initiated and managed by Donald F. Nelson, now professor emeritus of physics at WPI, during the 1990s, a time when concern over the link between residential radon exposure and lung cancer was growing. Nelson says the aim was to try to establish what level of radon exposure actually correlated with significant lung cancer risk and to establish a safety zone for home radon levels. “We were certainly not looking for a hormetic effect,” says co-author Joel H. Popkin of Fallon Clinic and St. Vincent Hospital in Worcester. “Indeed, we were stunned when the data pointed to that conclusion in such a strong way.”
In the study, the exposure of 200 individuals with confirmed cases of primary lung cancer to radon was compared to the exposure of 397 carefully matched, randomly selected control subjects. All subjects were 40 years old or older and had lived in their homes for at least 10 years. All of the cases and controls were residents of Worcester County in Massachusetts and were enrolled in the same health maintenance organization, Fallon Community Health Plan.
The results were statistically adjusted for factors known to be correlated with lung cancer risk, including smoking, occupational exposure to carcinogens, and level of education. The adjusted results show that the odds ratios of developing lung cancer fall below one (the no effect level) at radon exposure levels within the range measured in about 90 percent of homes across the United States (0-150 Becquerel per cubic meter of air, or about 0-4 picoCuries per liter). The Environmental Protection Agency (EPA) recommends that homeowners take remediation actions when household radon exposure levels rise above 4 picoCuries per liter, based on the belief that radon exposure presents a linearly increasing lung cancer risk (a view not supported by the new study in the low-dose region).
In a statistical analysis led by Richard E. Thompson, associate scientist in the department of biostatistics at the Johns Hopkins University Bloomberg School of Public Health, two mathematical techniques were used to compute the odds ratios of developing lung cancer. They each showed a statistically significant lowered lung cancer risk—a reduction of as much as 60 percent–over portions of the 0-150 Becquerel per cubic meter range.
The results of the current study do not fall within the “linear, no threshold” (LNT) model commonly used to analyze radon’s cancer risk (in fact, the current study calls into question the validity of that model). The model starts with cancer risks documented for exposure to high levels of radon (for example, by uranium miners) and extrapolates a considerable distance to risks at low levels (for example, for homeowners). In that model, the odds ratios of developing cancer rise linearly from one, beginning at a radon level of zero. The model has been used by the EPA to derive its estimate that 21,000 cancer deaths annually can be attributed to radon exposure, and also accounts for the common belief that there is no safe level of radon exposure.
Donald Nelson says the differences in the outcomes of this and previous studies may be attributable to key elements of the new study’s design. For example, he noted, care was taken to place radon monitors (for yearlong measurements) in areas of the home where the subjects spent the most wakeful time. Monitors were also place in the subjects’ present and former bedrooms and on any other home level where they spent as little as one hour per week.
The subjects’ exposures were then obtained by weighting the measurements according to the time typically spent near each detector. The results were further adjusted to account for how subjects’ home use changed with changing lifestyle (for example, transitioning from full-time employment to retirement). “Our analysis shows this to be an important improvement over exposure measures used by almost all other studies,” he said.
“It is important to note,” Nelson added, “that these new results do not dispute the lung cancer risk associated with higher levels of radon exposure experienced by uranium miners. Nevertheless, the results represent a dramatic departure from previous results and beliefs. Of course, a single epidemiological study is seldom regarded as definitive, so our results point to the need for new studies using our techniques.”
Nelson also noted that the study revealed a dramatic correlation between level of education and lung cancer risk. Subjects who had at least some college education were found to have only 30 percent of the lung cancer risk of those with less than a high school education. “While education has been found to be an important correlated variable in many health studies,” he said, “this is a particularly striking and statistically significant result, one found after smoking, job exposures, and radon were statistically adjusted for.”Research, Science Case Control Studies, Cause Of Lung Cancer, Cigarette Smoking, Community Health Plan, Environmental Stressors, Fallon Clinic, Fallon Community Health, Fallon Community Health Plan, Health Physics, Home Radon, low level radiation, Lung Cancer Risk, Popkin, Professor Emeritus, Radiation Hormesis, Radioactive Decay Product, Radon Gas, Repair Mechanisms, Residential Radon Exposure, Safety Zone, St Vincent Hospital, Worcester Polytechnic Institute Top
Posted on May 24th, 2009 2 comments
In 1980, Professor T.D. Luckey, a biochemist at the University of Missouri, published a study, entitled Hormesis With Ionizing Radiation (CRC Press, Boca Raton, FL; also in Japanese, Soft Science Inc., Tokyo), of over 1200 experiments dating back to the turn of the century reporting the effects of low-level radiation on biota ranging from viruses and bacteria through various plants and animals up to vertebrates. He found that, by all the criteria normally used to judge the well-being of living things, modest increases of radiation above the natural background make life better: they grow bigger and faster; they live longer; they get sick less often and recover sooner; they produce more offspring, more of which survive. The phenomenon of “hormesis”–whereby things that become harmful at high concentration are actually beneficial in small doses–is established in chemical toxicology. The effect is believed to result from stimulation and exercising of the natural immune system. What Luckey showed was that it applies also to radiation.
Some further facts that are consistent with this conclusion:
* Iowa, the state that the EPA found as having the highest average level of radon in the home, also has below-average cancer incidence. The mountain states, with double the radiation background of the US as a whole, show a cancer rate way below Iowa’s. Data from a study of 1729 U.S. counties shows the correlation between radon and lung cancer mortality to be about the same as for cigarette smoking; except that it’s negative: the more radiation, the less cancer.
* The same extends worldwide. The waters of such European spas as Lourdes, Bath, and Bad Gastein, known for their beneficial health effects since Roman times, all have high radioactivity levels. Areas noted for high radiation backgrounds, such as the Caucasus, southwest England, northwest India, have high longevity and low cancer incidence.
* British data on over 10,000 UK Atomic Energy Authority workers show cancer mortality to be 22% below the national average. For Canada the figure is 33%. (Imagine the hysteria if those numbers were the other way around!)
It appears, however, that the political consequences of announcing this to a public that has been saturated with contrary propaganda for over 20 years would be unacceptable. Although papers and conferences on radiation hormesis are now regular features of the scientific scene, they are ignored by the lawmakers and regulatory authorities. The continuing assumption of proportionate damage by tiny doses contradicts everything that has been discovered about cell metabolism and the mechanism of DNA repair since the early sixties.
If a little extra radiation is good for you, what optimum dose should our local health-food store recommend? Work reported from Japan puts it roughly at two “millirems,” per day. That’s about a tenth of a dental X-ray, or one coast-to-coast jet flight, or a year’s worth of standing beside a nuclear plant. For comparison, the level where the net effect becomes harmful is around two rems per day; 50 (note, we’re talking rems now, not millirems) causes chronic radiation sickness; 100 is lethal.
Perhaps tablets for those who don’t get enough regular exposure wouldn’t be a bad idea. A good way to use radioactive waste might be to bury it under radon-deficient homes. And perhaps cereal manufacturers should be required to state on their boxes the percentage of the daily dietary requirement that a portion of their product contributes. After all, if radiation is essential for health in minimum, regular amounts, it meets the accepted definition of a vitamin!
As a further note to put things in perspective, her are some figures comparing radiation exposures experienced by the average American from various sources, natural and man-made.
Annual estimated doses in mREMs per year:
All rocks contain traces of uranium. Radiation from the granite used in Grand Central Station exceeds the NRC limits for nuclear-plant operation. Grand Central Station wouldn’t get a license as a nuclear plant. Neither would the piers of the harbor at Dun Laoghaire, near where I live in Ireland.Nuclear, Radiation Hormesis Atomic Energy Authority, Bad Gastein, benefits, Cancer Incidence, Cancer Rate, Chemical Toxicology, Cigarette Smoking, European Spas, Ionizing Radiation, Level Radiation, low level radiation, Lung Cancer Mortality, Natural Immune System, Northwest India, Plants And Animals, Radiation Background, Radiation Hormesis, Radioactivity Levels, Soft Science, Southwest England, Uk Atomic Energy Authority, Viruses And Bacteria, vitamin R, Worke Top