A Very Short History of Radiation Hormesis

The extremely tall people on Niue Island (averaging height 6'6") receive 10 times more radiation from the soil than the world average. [Eugaster, Subradiation experiments concerning the concept of the natural radiation background, Aerospace Medicine, 35, 524, 1964.]

Why, you might logically ask, was the hormesis phenomenon not discovered until some eighty years after Roentgen, Becquerel, and the Curies made their contributions to radiation science? Why was there not an earlier Professor Luckey? [Professor Luckey is credited with coining the term "Radiation Hormesis" from his 1981 book Hormesis with Ionizing Radiation.]

Actually there was of sorts, and he, oddly enough, was also a professor at the University of Missouri. In 1896, Professor W. Shrader inoculated guinea pigs with the diphtheria bacillus. [Shrader, W. Experiments with X-rays upon germs. Electrical Engineering, 22, 170, 1896.]

The group exposed to X-rays prior to inoculation survived; the unexposed cohort died within twenty-four hours. Shrader, in the same series of experiments, was apparently the first person to discover that "Roentgen Rays" could be used to kill germs.

During the early twentieth century, radiation was used for a variety of experimental therapies, but the doses were generally far above hormetic levels and may well have caused more harm than good. Patent medicines such as "Radithor" (more on this in chapter 24) were popular, with single doses having nearly a million times the daily radium intake allowed by current government regulators. Hundreds of thousands of vials of elixirs were consumed without any widespread harm occurring and with a sizable number of "miracle cures" being reported. Few controls, however, were employed to scientifically assess the actual worth of the treatments leaving one to believe that most of these "cures" may have been either the product of advertising hype or a placebo effect.

Medical research wasn't the big draw for world-class physicists. We might remember that in the early days of radiation experimentation important discoveries were being made almost daily, while health considerations - except, possibly, for the annoying, minor and superficial skin "beta burns" - were considered to be of no consequence. The doses of radiation these unprotected experimenters received are estimated to exceed by thousands of times the maximums under which today's nuclear industry workers are allowed to continue on the job.

Madame Curie, discoverer of both polonium and radium, offers a good example of the "non-standards" of the day. [In 1516, a silver lode was discovered in St. Joachim's Dale (Joachimsthal), which was - naturally - confiscated by the government of Count von Schlick. Coins minted from this mine were known as Joachimsthalers, which (for obvious reasons) came to be known as thalers - in English, dollars. It was from this mine that the Curies obtained pitchblende - an ore rich in uranium and its daughters, radium and polonium.]

It is anecdotal that whenever Marie Sklodowska [in case you were curious why she named her first discovery for Poland] Curie walked into a room, electroscopes immediately discharged. [Gold is so malleable that it can be pressed into leaves less than 1/10,000 of an inch thick. If you hang two pieces of leaf in an air-filled jar, with provision to charge both - you have an electroscope. Charging the leaves with the same polarity causes them to "push apart" and, because they are so light, the electrostatic "pushing" force exceeds the gravitational force that would cause them to "droop" into a vertical position. Such devices were used to assay the content of uranium ores - not from the non-penetrating alpha radiation of the uranium, but from the accumulated daughters of which the gamma ray emitting radium was a significant component. Air, when ionized, is a conductor that discharged the electroscope at a rate proportional to the amount of ionizing radiation present.]

It is almost certain that she had an enormous lung burden of radium - the element she was extracting from uranium ore - which took quite a bit of patience, since there are only about 0.003 grams of radium per ton of ore. Madam Curie died almost certainly from the effects of long-term and extremely high doses of radiation. Yet, at age sixty-six, she still exceeded by ten years the life expectancy of her day.

Later in the century, the subject of hormesis would have doubtlessly been trifling compared to other matters. From August 1939 - when a letter from Albert Einstein was delivered to Franklin Roosevelt recommending the development of an atomic bomb - until the end of World War II, the focus of virtually the entire nulcear physics community became the Manhattan project. (This venture, equivalent in size to the total automotive industry at that time, is described in fascinating detail in The Making of the Atomic Bomb [Richard Rhodes, Simon & Schuster, New York, 1986].)

Certainly the scientists were aware of potential dangers from radiation - especially the highly penetrating neutrons from "atomic piles" - but these risks were minimal, compared with the reality of thousands of deaths from the war every day. Concerns about low-level radiation - either harmful or beneficial - weren't even on the radar scope.

Interestingly, the only health physics experiment I've ever come across that occurred during the Manhattan project was indicative of radiation hormesis:

"In 1943, a group of [radiation scientists] on the Manhattan District Project were worried about the unknown toxicity of uranium. They grew a colony of rats in an atmosphere laden with sufficient uranium dust to kill them fast (the Manhattan Project didn't have time for fancy radiobiologists). As a control, a similar colony breathed clean air. After several months, nothing happened, but eventually the rats lived out their natural lifespans, with one surprise: the first health physics experiment demonstrated that rats who breathed uranium dust lived longer and were happier (i.e., had a better reproductive history) than normal rats. Not a tumor in the bunch." [From a letter by Marshall Brucer, M.D. to Time magazine (from the files of Petr Beckmann).]

During this period there are reports of relatively minor medical experimentation to determine the effect of ionizing radiation on the healing of wounds. The exposure levels, however, were high (1 Gy or 100 rem) - suggesting its use as a bactericide. The availability of antibiotics in 1942, and the post-Hiroshima bombing concerns over high-level dangers, caused a loss of interest in research of this nature by the end of World War II.

After the war, the Japanese cities of Hiroshima and Nagasaki became laboratories for research on the effects of radiation on humans. But the focal point was on the high-dose subjects - in particular on their excess cancers and the possible mutational effects on children. When low-dose victims showed beneficial health effects, the data were ignored as being anomalies (a fancy scientific words for "it doesn't fit in with what we're expecting").

Luckey addresses this subject:

"Statistical analysis of observed data was missing in many reports of experiments involving low doses of ionizing radiation. Most of the reports simply indicated that an unexpected phenomenon had been observed, but the researchers failed to pursue it systematically... Any unexpected result was rejected by the 95% rule: One experiment in each twenty was accepted as a variant. Closer inspection showed this was a consistent result; it usually occurred in the group exposed to the least radiation, the only one in the hormetic range. Hormetic data were ignored because they did not fit the models of the zero thesis." [Radiation Hormesis, p. 45.]

When someone really writes a history of radiation hormesis, the first "official" recognition of the phenomenon will go to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in a 1994 report "Adaptive Responses to Radiation in Cells and Organisms":

"Manifestations of the adaptation described in mammals after exposure to low doses of radiation include accelerated growth rate in the young, increase in reproductive ability, extended life-span, stimulatory effects on the immune system, and a lower than expected incidence of spontaneous tumors."

You might want to read that again.

Hormesis U.: A Review

Before leaving dear old Hormesis U., here is a short review to see if you've got a handle on the curriculum. You should know...

• Elements are identified by the number of protons in the nucleus (atomic number).
• Isotopes of elements have different numbers of neutrons (n + p = atomic weight).
• Atoms of some isotopes are stable, while others are radioactive and, over time, will disintegrate (decay) into other elements of a lower atomic number.
• Alpha and beta particles have a short range (a few inches and a few feet respectively).
• Gamma rays and X-rays can penetrate several inches of steel or feet of concrete.
• The half-life of a radioactive isotope is the time it takes half of the original amount to decay; after thirty half-lives the original amount is considered to be gone.
• The longer the half-life, the lower the activity of an isotope.
• A curie is 37 billion becquerels.
• A pCi is a picocurie and is equal to one-trillionth (10^-12) of a curie.
• Absorbed doses of radiation are measured in rads or grays; 100 rads equal 1 gray.
• Biological doses are measured in rems or sieverts; 100 rems equal 1 sievert.
• The absorbed dose and the biological dose are the same for gamma and X-rays. 
• A fatal acute dose is about 4 sieverts or 400 rems (50% fatalities in thirty days) when received in a relatively short time (a few days or less).
• Radiation sickness occurs at about 1 sievert or 100 rems (50% of those exposed over a short time). 
• Doses below 1 sievert or 100 rems (100,000 millirems) have no immediate biologic effects but are generally thought to increase the risk of cancer in the future.

Thanks for your attendance at Hormesis U. No doubt you'll find the rest of the information on radiation hormesis much more understandable now than when you were a mere freshman. Oh, and be sure to send in your contribution to the Alumni Fund.

Acute Radiation Syndrome

Table 8 – Acute Radiation Syndrome
Subclinical Range 0 – 100 rads		Therapeutic Range 100 – 500 rads			Lethal Range 500+ rads
		100 – 200	200 – 300	300 – 500	500 – 2000	2000+
Appropriate Action	None	Clinical surveillance	Therapy effective	Therapy promising	Therapy palliative (comfort patient only)
Incidence of Vomiting	None	100 rads: 5% 200 rads: 50%	75%	75%	100%	100%
Delay Time	n/a	3 hours	2 hours	1 hour	3 min.	3 min.
Main Organs Affected	None	Blood Forming Tissue			Gastro-intestinal Tract	Central Nervous System
Characteristic Signs	None	White Blood Cell Decrease	Fatigue, infection, erythema, sterilization, loss of hair above 300 rads, hemorrhage		Diarrhea, fever, electrolyte imbalance, bleeding	Convulsion, coma, loss of muscle control, lethargy, tremors
Critical Period	n/a	n/a	4 – 6 weeks		5 – 14 days	1 – 48 hours
Post-exposure Therapy	Assure of Safety	Blood analysis; assure of safety	Blood transfusion; anti-biotics	Possible bone marrow transplant	Maintain electrolyte balance	Sedatives
Outlook	Excellent	Excellent	Good	Guarded	Hopeless	Hopeless
Convalescent Period	None	Several weeks	1 – 2 months	Long	n/a	n/a
Death Rate	None	None	0% - 40%	40% - 100%	90% - 100%	100%
Death Within	n/a	n/a	2 – 4 weeks		2 weeks	2 days
Cause of Death	n/a	n/a	Hemorrhage, infection		Dehydration	Respiratory failure; heart attack

Table 8 Source: "Terrorism With Ionizing Radiation General Guidance: Pocket Guide," produced by the Employee Education System for the Office of Public Health and Environmental Hazards, Department of Veterans Affairs.

Some may think that certain data are emphasized in this and other chapters in an attempt to minimize the dangers of exposure to radiation. This is not at all true. I am trying to put the dangers in perspective and eliminate the Pavlovian negative response to even the very mention of the subject. Table 8 shows the accepted syndrome from short-term exposures. Please note that this table is in rems (not millirems) and can be mentally converted to centisieverts (cSvs) of the same numerical value. Radiation can obviously be very dangerous. But so can an unreasonable fear of radiation.

The International Standard (SI) Units

In the International Standard measuring system, there is no equivalent for the roentgen - which is just as well as far as we're concerned because it is seldom used in relation to human exposure. The following relationships exist between the USA and SI units:
100 rad = 1 gray or Gy
and
100 rem = 1 sievert or Sv

One gray or sievert represents and enormous amount of radiation - about four times as much as a U.S. resident would normally receive in a 76-year lifetime. Smaller units, the centigray, cGy, and the centisievert, cSv, are more commonly used. These conveniently convert to USA units -
1 cGy = 1 rad = 1000 millirad (mrad)
and
1 cSv = 1 rem = 1000 millirem (mrem).

If learning these measuring systems seems too complicated, try learning a few reference exposures and compare the value in question to these. Here are the ones I use, which then give me a feel for other values. After a while, they start all becoming second nature.

• Sleeping with your spouse for a year - 1 mrem or 0.001 cSv (for the ambitious learner, 0.01 mSv). Since your spouse emits gamma rays; the rads, rems, cSv and cGy are all the same. In almost all of the cases (except internal radium and plutonium) that we're going to be examining, this will be the case.
• Background radiation in the United States - 300 mrem or 0.3 cSv. In the International System, the millisievert - one-tenth of the centisievert - is often used in this range. Our normal background dose in this unit is 3 mSv. Since a good portion of this radiation is from radon sources (an alpha emitter); rads, rems, Gy, and Sv are not interchangeable.
• Radiation sickness - ensues at about 100,000 mrem, or 100 rem, or 100 cSv, or 1 Sv. Because doses of this magnitude are usually low LET radiation, units of 100,000 mrad, 100 rads, 100 cGy, or 1 Gy may be used interchangeably. By the way, sickness results from an acute exposure of 1 Sv over a period of a couple of days or less. The same radiation over a longer exposure time gives no symptoms.

If you'll commit these three points to memory (or place a bookmark here), it will give you some frame of reference with which to compare other doses. Your bookmark will also give you easy access to Table 7, which gives some typical millirem and cSv values for other exposure situations.

Table 7 – Selected Radiation Doses Per Year
Source of Exposure	mrem	cSv
Nuclear plant within 50 miles	0.01	0.00001
Average Three Mile Island dose	0.1	0.0001
Color television	1	0.001
One coast-to-coast jet flight/trip	5	0.005
Border of nuclear power plant	5	0.005
From food	25	0.025
Cosmic radiation	27	0.027
Building materials	34	0.034
Your own blood (Potassium 40)	45	0.045
On-site for duration, TMI accident	80	0.080
One shoe X-ray (SXR)	175	0.175
Grand Central Station	525	0.525
Living on Colorado plateau	600	0.6
Barium enema	800	0.8
Max permissible for nuclear worker	5,000	5
Radiation sickness (50% people) [acute exposure over a day or two]	100,000	100
Death (50% of people) [acute exposure over a day or two]	400,000	400

Measuring Radiation Doses

In the USA system of radiological measurements, there are three somewhat confusing units for measuring the exposure to and doses of radiation:

• the roentgen (pronounced rent'-gen),
• the rad, and 
• the rem.

To understand these you might imagine yourself on a sunny beach. The roentgen is analogous to the intensity of the sunlight striking the beach. The rad (radiation absorbed dose) corresponds to the amount of sunlight absorbed by your skin, while the rem (roentgen equivalent man) is comparable to the biological effect of the sunlight exposure. In the case of the rem, however, the difference in its effect is not due to your sunscreen, skin pigment, or hours spent in the tanning salon - but in the type of radiation being absorbed.

You may recall that the different types of radiation were either particles (alpha and beta rays, protons, neutrons) or high-energy photons similar to light (X- and gamma rays). Except for beta rays - which are electrons having some 1/1836 the mass of protons or neutrons - the particles, because of their large masses, have a more catastrophic effect when colliding with a cell in the body. For this reason the quality factor - usually designated as Q - is used to adjust the absorbed dose to its biological counterpart, the rem.

Mathematically, rads x Q = rems.

Fortunately, most of the exposures we will be referring to in the study of hormesis are gamma and X-rays where Q is equal to one, allowing rads and rems to be used interchangeably. (Your radiologist, dental hygienist, and others working with X-rays will usually talk in terms of rads or millirads - but these are the same as rems and millirems, because it is the X-ray source that produces the radiation.) There is one other term with which you should have at least a vague familiarity - Linear Energy Transfer or LET. Beta, famma and X-rays are considered low LET radiation, which means they have a Q of one. High LET particles can have Qs up to 400. A typical alpha particle has a Q of four.

[Wilhelm Roentgen (1845-1923) discovered an unknown emission (X-rays) from cathode ray tubes. It still happens today - that's how X-rays are made today. Incidentally, your TV screen is a cathode ray tube, and it emits many times the radiation we get from nuclear power plants. Somehow this fact escapes notice of the TV doomsayers.]

Getting a Handle on Radiation Doses

How many atomic explosions in our cities would you accept before deciding that nuclear power is not safe - no complexities, just a number? - Ralph Nader, 1974

A significant source of confusion regarding the measurement of radiation parameters is the simultaneous use of two systems of units. As noted in chapter 7, "activity" is measured in curies in the USA system and Becquerels in the International System of units. A similar duality is found in the measurement of "doses" of radiation, as will be discussed in this chapter.

The question arises as to which units should be used in this book. Personally, I think in terms of the USA units and find that most people actively involved in radiation related disciplines in the United States do likewise. On the other hand, most scientific papers are written using the S.I. values - certainly all the recent ones on hormesis.

Since neither way will satisfy all readers, it will be the policy herein to use both in the next few chapters - generally the S.I. units followed by the USA units in parenthesis unless a quotation or other source is expressed in the USA units... in which case the S.I. units are given parenthetically. Hopefully this repetition will get you accustomed to both systems of units and the relationship between them. Later chapters will use the same units as found in the source material. The plan is for you to become familiar with both by then and to make any necessary conversions in your head. (Or refer to Table 6 on page 51 or to Table 7, coming up on page 56, another good place for a bookmark.)

We will start with the more familiar (at least to me) USA units.

Specific Activities

When interested in relatively low-level radioactive material, the picocurie, or pCi (one-trillionth of a curie, remember?), is used. In Table 6, the activity is in pCi per liter and in Bq per liter. [You will also run across Bq per cubic meter (Bq/m3) in some radon studies. Multiply Bq/l by 1,000.]

Table 6 – Specific Activities of Common Substances
Material	Picocuries/liter	Becquerels/liter
Normal air	2	0.074
Typical radon level in homes	3	0.111
EPA limit: Ra-226 in drinking water	5	0.185
Nuclear power plant leak	15	0.555
“Contaminated” milk at TMI*	22	0.814
Rainwater **	360	13.3
Whiskey	1,200	44.4
Salad oil	4,900	181.5
Spa waters of Bad Gastein	16,200	599
Drinking water in Maine***	53,700	1,987
*The increase in radioactive iodine in Harrisburg after the Three Mile Island “disaster” was 1/20 that caused by Chinese A-bomb tests in 1976. You remember how Jane Fonda and Ralph Nader protested those, don’t you?
**Measured at Santa Fe, 5/11/1986. (Probably atmospheric carbon 14 and wind-blown potassium 40 salts.)
***Based on an average of 226 samples. Radiation Controversy, Ralph Lapp, Reddy Communications, 1979.

Since most Americans have no idea what danger might lurk in a glass of water having 200 picocuries per liter, we are at the mercy of those who might use this lack of knowledge to their political advantage. Professor Petr Beckmann pointed out that activity in a well-publicized reactor leak at Indian Point power plant outside New York City was equivalent to that in a pint bottle of salad oil. Without this knowledge, an interested citizen would be led to believe (a) nuclear power was unreliable, and (b) such technology was a danger to life and limb - exactly what anti-techologists Nader, Commoner, Ehrlich and their fellow primitivists would have us believe. Exactly the opposite of the truth.

You might want to bookmark this page, for easy reference to Table 6 as you read on.

In answer to the question posed in the chapter title, 100 picocuries is the approximate activity in a handful of average soil produced by the disintegration of potassium 40. (I always knew there was something dangerous about working out in the yard.)

Next we'll take a look at how the effect of ionizing radiation on the human body is measured.

100 Picocuries - That's a Lot! (Or is it?)

Since most Americans have no idea what danger might lurk in a glass of water with 200 picocuries per liter, we are at the mercy of those who might use this lack of knowledge to their political advantage.

Imagine sitting in a chair three feet away from a gram of an unknown radioactive metal, about the size of a penny, on the floor in front of you. Should you be concerned? I know I would be - at least until I knew more about what it was. Obviously we would be interested in what type of radiation was being emitted. It if were alpha or beta particles, there would be no problem as the 3 feet of air would stop any significant amount. But what if it were gamma rays? Then we would want to know just how "active" the source was - with the activity of a radioactive source being measured in the number of atoms that disintegrate every second.

Let's suppose our one gram of material is radium, specifically 226Ra. Would you care to guess the number of disintegrations per second? A mere 37,000,000,000 (37 billion)! This, by the way, is the number of disintegrations defined as 1 curie, or 1 Ci, since the curie is defined as the activity of one gram of radium. You needn't run away, but you might not want to hang around. If it were one gram of cesium 134, a quick exit would be advisable. [Cesium 134 is a gamma and beta emitter that has about fifteen times the activity of the Goian cesium 137, which is only a beta emitter.]

The curie, a United States (USA) unit, is still in common use but is gradually being replaced by the International Standard (SI) becquerel or Bq, which is defined as one disintegration per second. Obviously, then, 1 curie is equal to 37 billion Bq - not exactly the easiest conversion constant to work with, especially when you have to go the other way: 1 Bq = 2.7 x 10^-11 Ci = 27 pCi.

A few elements of interest and their specific activities - that is, their activity per gram - are given in Table 5.

Table 5 – Specific Activities of Selected Elements
Element	Curies	Becquerels	Half-Life
Thorium 232	0.000000166	4,316	14.05 billion years
Uranium 238	0.000000333	12,300	4.47 billion years
Potassium 40	0.00000722	267,200	1.27 billion years
Radium 226	1	37 billion	1,620 years
Strontium 90	139	5,143 billion	28.8 years
Cesium 134	1,290	47,900 billion	2.06 years
Iodine 131	124,000	4,588 trillion	8.04 days
Tellurium 133	113,000,000	4,200,000 trillion	12.4 minutes

Note that the half-life of the low activity 238U is very long - 4.5 billion years, while one-half the very active 131I isotope is gone in 8.04 days. We would expect this, since there are a finite number of atoms in a gram of any substance, and if the rate of decay (i.e., the activity) is high, it will take less time for the substance to lose its radioactivity. This is verified by the very low relative activity of the primordial radionuclides such as thorium, uranium and potassium, which have extremely long half-lives since these were presumably created at the same time as the Earth - estimated by most cosmologists as some 4.6 billion years ago. The shorter half-life isotopes - say a mere few million years or so - are long gone, although some are being replaced by decay products of the low activity elements.