All things are good in moderation …including radiationFor years U.S. nuclear utilities, radiographers, hospitals and others using radioactive materials have labored under a set of regulations which is based on the assumption that any and all radiation is harmful to living beings. While there is no doubt that high levels of radiation can be lethal, many scientists have argued that this “linear hypothesis” assumption is too conservative and that there is a threshold dose below which radiation does not harm human beings. Now, evidence continues to build that, in fact, low levels of radiation are actually life-enhancing. This phenomenon is known as radiation hormesis.
In a recent paper, Dr. Bernard Cohen of the University of Pittsburgh continues to explore the scientific basis for the linear hypothesis. Cohen`s paper, “Lung Cancer Rate vs. Mean Radon Level in U.S. Counties of Various Characteristics,” (Health Physics volume 72, No. 1, January 1997) effectively punctures the regulatory assumption and provides strong support for the healthy effects of low-level radiation. Cohen gathered data on naturally occurring in-home radon levels for more than 1,600 U.S. counties. These populous counties represent nearly 90 percent of the U.S. population. He grouped the counties into areas with similar exposure levels, then averaged the lung cancer incidence rate for each grouping.
After correcting for the incidence of lung cancer due to smoking, Cohen found that lung cancer rates actually decreased with increasing radon levels up to a point. The analysis showed a lung cancer reduction of nearly 30 percent (with a 95 percent confidence level) as the in-home radon concentration increased from 0.4 pico curies/liter to 4 picocuries/liter. Cohen`s work shows a statistical minimum occurrence of lung cancer at radon concentrations of approximately 4 to 5 picocuries/liter.
As with any statistical study, the results do not show a cause-and-effect relationship. Instead, the results are indications that there may be some effect. Cohen has worked for three years to identify other possible causes for the reduced lung cancer incidence. He has examined such variables as population density, age, urban vs. rural environments, availability of medical care, income levels, occupation, etc. He has recalculated his data more than 100 different ways and has not been able to find a factor that affects the basic shape of the incidence curves he calculated. Thus, he has concluded that there is strong evidence that a low level of radiation is actually good for human health.
Forty or 50 years ago people paid to sit in radium mines and benefit from the healthful effects of the low-level radiation. Regulations based on the linear hypothesis description of radiation damage stopped this practice. Now, as we continue to learn more of the mysteries of the universe, the new evidence seems to support yet another folk medicine practice.