Frederic B. Jueneman, FAIC | R&D Magazine | Copyright 1995 by Frederic B. Jueneman

Late this past October I took one of my grand kids to the Open House at The Lawrence Berkeley Laboratory complex, a Department of Energy facility nestled high in the hills overlooking the UC Berkeley campus and devoted to problem solving in energy, environment, health, and basic research. Included in this array is a Genome Research Lab, one of three such labs supported by the DOE to explore the human DNA genome through robotics and digital microscopy. The exposition attracted students from all walks of life.

In Bldg. 2 is the historically aging Betatron, last powered up in 1993, a relic of the Nobel­laden experiments of yesteryear. But dwarfed by this massive cyclotron was a minuscule lexan window exhibit of a neon­filled multi­stage spark chamber, where cosmic rays from “somewhere out there” zapped through every few seconds, silently ionizing the high­voltage charged neon gas with segmented orange­colored streaks, first at one angle then at another.

The school lesson here, as a student attraction, is that such energetic cosmic particles have been soaking the Earth for untold eons, noiselessly bathing us in an ionizing shower that has possibly defined the radiation threshold of our quality of life since the beginning of biological time.

By happenstance, shortly after this fascinating excursion in Berkeley I attended the American Nuclear Society gathering across the Bay in San Francisco where a series of international interest meetings were devoted to low level radiation and its concomitant effects on our present quality of life. The average person living in the US, for example, gets about 360 milli-rems radiation per year from both cosmic and terrestrial sources. The cosmic sources are from galactic and extra­galactic particles while terrestrial origins are principally from diffusion of radon gas. Estimates range as high as 15,000 particles per second per person.

Some curiosities were brought out at this ANS meeting that defied explanation. Bernard L. Cohen, professor of physics at the University of Pittsburgh, had made an independent comprehensive survey of some 1600 counties throughout the US, a study that purportedly was designed to once­and­for­all define if not sustain the theory of linear, no­threshold distribution on cancer­induced radiation as espoused by the Nuclear Regulatory Commission. However, this was not what he found at all.

The standard chart on such things begins with a zero­level radiation threshold and rises linearly toward some arbitrarily high mortality dosage. But, up until some several hundred milli-rems there was no discernible effect. What was shown was a slight but statistically significant decrease in radiation­induced carcinomas at around several hundred milli­rems. Furthermore, the statistical curve then dipped downward giving a negative slope, and only returned to rise above the baseline at about 5 rems per year, some fifty times the annual recommended limit by the NRC. Then begins an extensive gray area where precious little is known up to about 100 rems per year.

This finding was supported by researchers from Japan, who in the course of their own investigations had also used the statistics supplied by the US for Hiroshima and Nagasaki, where a study of nearly 80,000 survivors were divided into control and exposed groups. The normalized distribution of carcinomas showed about 120 more incidences in the unexposed group, which ran counter to every expectation.

The question is, what’s going on?

The statistics for Denver and the Colorado plateau are also skewed. These folks get an additional 90 millirems per year from both cosmic and terrestrial sources, but have less than average incidences of cancer. This same skewness exists for people who live in higher radon­level areas, seemingly contrary to what we read in the mass media. Moreover, those persons having plutonium­powered cardiac pacemakers can add 100 milli-rems to their annual dosage.

What this seems to boil down to is what is called hormesis, a biological term that describes the effect of a stimulating insult by a toxic substance at nontoxic levels. Many such chemical toxins are known, such as arsenic, copper, or selenium, which play minor but significant hermetic roles in metabolism at relatively low concentrations.

Does this mean that radiation also is a necessary “nutrient” in the metabolic broth, that there’s a minimum daily requirement?

I would wager that it does. For one thing, Homosapiens has proliferated and thrived for mega years in this milieu. For another, mankind has extended its individual life span substantially over the last few centuries, due to better living conditions, increased nutrition, and more effective medical and sanitary practices. Humankind now encounters otherwise rare physical insults and diseases because we live long enough to experience them.

In like manner, radiation exposure at elevated levels of up to 100 rems is probably only significant in the aging process, and we haven’t yet really learned how to control that.