A Perspective on Ionizing Radiation Exposure After the Japanese Wake-Up Call – Part I

Over the years my overall purpose in writing the Moss Nutrition Report has been to present what is currently on my mind from a clinical/nutritional standpoint based on my personal studies and input from you.  As we have all seen, up until March 11, 2011, our overriding concern has been finding ways to deal with, as noted in the September 9, 2009 issue of The New York Times, “…a tidal wave of chronic illness…”  Hence, for the last several months I have been addressing ways that we can both understand and optimize the health of the massive amount of patients who are now coming our way who have suffered chronically for years.  While this concern certainly continues to weigh heavily on all of us, since March 11 virtually all of our minds have been primarily focusing on a tidal wave of another sort; one that is much more real, graphic, and dare I say terrifying than the conceptual one described in the above quote.  Because of this, I am going to take a break from addressing the needs of chronically ill patients in the Entry Level Clinical Nutrition™ series and focus on a nutritional issue that I would suspect has been lightly and sparingly regarded by most of us over the years, including myself: the nutritional needs of those individuals exposed to excessive levels of ionizing radiation.

It is both interesting and ironic that Japan was twice the location of events that forever changed our world view of man’s use of nuclear technology.  The first, of course, was an outgrowth of one of history’s most destructive wars that only a very few of us, at this point, actually experienced.  However, the second, an outgrowth of our efforts to use nuclear technology for peaceful, lifestyle-enhancement purposes, is very fresh and indelibly branded onto all of our minds.  Right now, as of 2:15 PM ET on April 8, 2011, the very moment I am doing the final proofread of this newsletter, it appears that the crises is moving into a more chronic phase where low levels of radiation are still being released with total resolution months, if not years, away.  However, at the time you read these words, will the crises be vastly different, leading to even more concern with possible panic and fear?  While all of the most credible indicators at this point suggest that the risk of a panic-inducing crisis is remote, no one can say with 100% certainty how events will play out in relationship to radiation levels and the concerns/fears about those levels.  Nevertheless, I do believe with virtually absolute certainty that, even if the realities of the nuclear disaster and the concerns/fears about it have been substantially reduced by the time you read this, as with the decades after August of 1945, we will never view nuclear reactors the same way again.

As clinical nutritionists, have we been too complacent in addressing issues of excessive ionizing radiation exposure with our patients?  I realize that this is a difficult question to answer.  However, my reply to this question would be to state that in the 24 years I have been writing the Moss Nutrition Report I have never once written on the subject.  Does this represent complacency, ignorance, or a simple reflection of our priorities over the last 24 years up until March 11, 2011?  Frankly, I’m not sure.

However, it is a priority now and will continue to be thus for the foreseeable future – no matter how events ultimately play out at the Japanese reactor, at the immediately surrounding areas, and at whatever location humans might be where increased exposure to ionizing radiation occurs, no matter how minute.  Therefore, even if the sequelae of March 11 are, in just a few days, weeks, or months, completely benign from an ionizing radiation standpoint, I feel that we as clinical nutritionists should still take on a “forewarned is forearmed” attitude and make the time to educate ourselves and our patients about the impact of excessive ionizing radiation and its interrelationship with optimal nutrient intake.

One more thought on how we should respond if, within a short period of time, all risk from the Japanese reactors evaporates away.  As I mentioned, we should avoid a natural tendency to return to our former complacency.  Why?  While you may be able to think of more reasons, I can give two that, unlike the Japanese reactors, are sources of chronic, low grade radiation that we have willingly decided to live with.  The first is cell phones.  Does the radiation they emit pose a risk clinically?  The research so far has been suggestive even though no concrete data, as far as I know, has been presented up to this point.  The second is all the smaller exposures we experience daily such as radiation related to air travel that, while as isolated entities pose virtually no risk, do add up.  Are all these small exposures that add up a risk clinically?  As with cell phones, no one really knows for sure as of now.  However, one conclusion we may be able to settle upon with reasonable certainty is that, because they all add up, it may be possible that, for certain patient populations, even a minute amount that comes from the Japanese reactors may be “the straw that breaks the camel’s back” so to speak.  Therefore, I want to again emphasize that, even if the Japanese nuclear disaster as an isolated entity ultimately leads to no risk worldwide, it is my opinion that we can no longer live in a state of complacency and ignorance in relation to the issue of ionizing radiation and illness.

Fortunately, even though the interrelationship between ionizing radiation and clinical nutrition has not been foremost in our minds during the last few years up until March 11, it has been on the mind of many researchers, largely in relation to the atomic bombs mentioned above plus the impact of radiation therapy, space travel, and, of course, Chernobyl.  Because of this, I have been able to find an impressive body of published research on this relationship.  Certainly, as you might expect, much of this research relates to the use of potassium iodide.  However, it also involves an aspect of the relationship that I would suspect many of you are not aware, the impact of antioxidant nutrients on ionizing radiation.  All of this and more will be detailed in the series that follows as I highlight research that quite possibly, in retrospect, I should have emphasized a long time ago.

SOME THOUGHTS ON FEAR

While my primary intent in reviewing all the papers that follow is to educate and inform, I have another purpose that may be equally important, if not more so.  Several years ago, during my iodine series, I presented some research that made it clear that the fear which very predictably follows events involving the unknown can not only adversely affect our ability to intelligently deal with the events but can sometimes take a toll on health that is equal or greater than the toll taken by the events themselves that caused the fear.  Concerning radiation, the relative impact of fear of certain events compared to the impact of the events themselves was noted in a fascinating article by George Johnson that appeared in the March 27, 2011 edition of The New York Times.  In that article the author stated the following about the impact of Chernobyl:

“The most debilitating effect, one investigator said, has been ‘a paralyzing fatalism,’ a malaise brought on by an alien presence that almost seems alive.”

Given the news that is coming from Japan right now, fear is certainly expected and justified.  However, fear in relation to a disaster of the magnitude we are witnessing can lead to a sense of helplessness and the kind of malaise mentioned above.  Unfortunately, as suggested by Mr. Johnson, this malaise can paralyze us from looking at the situation logically and dispassionately, an approach that will most often lead to the best solutions on how to protect ourselves from the world events we are powerless to alter.

With the above in mind, it is my hope that what I am about to present in this series will not only educate and inform, but instill confidence and inspire.  As you will see, the doomsday scenarios often conjured up with any discussion of environmental radiation are not foregone and inevitable conclusions.  In contrast, a large body of research that involves potassium iodide but is by no means limited to potassium iodide makes it clear that we do have options when considering whatever comes from Japan and how it adds to the cumulative load from all the other forms of radiation we now accept as part of our daily routine.  Therefore, I not only view Japan as a horrific disaster but as a wake-up call telling us to leave the complacency that existed before March 11th behind and, as stated by Dr. David Brenner, director of the Center for Radiological Research at Columbia University in the March 29, 2011 edition of The New York Times, take action:

“[Dr. Brenner] thinks the events in Japan should be a call to action for the United States.”

While Dr. Brenner makes it clear that he is referring to the aging nuclear reactors in the US, I interpret Dr. Brenner’s “call to action” from a broader perspective.  Given that cumulative radiation exposure, whether it is from aging nuclear reactors or the sources I have mentioned above, is not going away anytime soon, there is much that we can do even though we are not expert nuclear physicists.  I believe we can take action that, while it will receive considerably less publicity, is every bit as important as that which will hopefully be taken by those involved with the future of the nation’s nuclear reactors.  For, we can take action that can be truly effective in both optimizing the metabolic pathways that can be adversely affected by environmental radiation and minimizing the fear that can have as great an impact on these metabolic pathways, if not more so.

A CAVEAT CONCERNING THE FOLLOWING REVIEW

As we all know, certain supplement companies, often found on the Internet, have been known to use world events such as this, that involve both nutrient metabolism and large amounts of fear, as a marketing opportunity to peddle supplemental “panaceas” that can quickly and easily with little pain or inconvenience “cure” or “prevent” negative effects of the world event.  Given that I will be mentioning nutrients that are sold by Moss Nutrition, I want to make it abundantly clear that all I will be mentioning is not a “cure” or “prevention” for anything.  In contrast, the message I want to deliver is that a large volume of published research suggests, by optimizing nutrient metabolism via dietary changes, lifestyle modifications, and selected use of key supplements, we can reduce the negative impact of low to moderate levels of ionizing radiation.  Nothing I will be mentioning should be construed as a cure or prevention for acute radiation sickness that occurs with major nuclear exposures such as what is being seen in the immediate vicinity of the Fukushima Dai-ichi reactors.  In such situations, approaches involving extremely high levels of potassium iodide ingestion (130 mg) and other aggressive measures are appropriate which are beyond the scope of the review that follows.

WHAT EXACTLY IS THE IMPACT OF IONIZING RADIATION ON LIVING SYSTEMS?

Based on the research I will present, one of the most interesting nutritional substances in relation to protection from the effects of ionizing radiation is melatonin.  While I will be discussing the specific relation between melatonin and radiation later, I would first like to review portions of two papers on melatonin and ionizing radiation that address the specific cellular and metabolic impact of ionizing radiation.  The first quote I would like to present comes from “A radiobiological review on melatonin: A novel radioprotector” by Shirazi et al (1) which highlights some radiation basics:

“The absorption of energy from radiation in biologic material may lead to excitation or to ionization.  If the radiation has sufficient energy to eject one or more orbital electrons from the atom or molecule, the process is called ionization, and that radiation is said to be ionizing radiation.  The important characteristic of ionizing radiation is the localized release of large amounts of energy.  For convenience it is usual to classify ionizing radiation as electromagnetic (x- or γ-rays) or particulate (electrons, protons, α-particles, neutrons, negative πmesons and heavy charged ions).”

How does ionizing radiation cause damage?  The authors state:

“It has long been recognized that the damaging effects of ionizing radiation are brought about by both direct and indirect mechanisms.  The direct action produces disruption of sensitive molecules in the cells whereas the indirect actions of ionizing radiation occur when it interacts with water molecules in the cell, resulting in the production of highly reactive free radicals, such as .OH, .H, and eaq .  High energy radiation breaks chemical bonds and this creates free radicals, like those produced by other insults as well as by normal cellular processes in the body.  The free radicals can change other chemicals in the body.  The half life of these free radicals is extremely short, (10-6-10-10 seconds); however, they immediately react with any biomolecules in the vicinity and produce highly site-specific oxidative damage.  These changes can disrupt cell function and may kill cells.  An estimated 60%-70% of tissue damage induced by ionizing radiation is believed to be caused by .OH radicals.”

Before continuing, I do want to emphasize the sentence in the above quote that points out that the free radicals produced by high energy radiation are exactly the same as those produced by certain normal bodily functions.  Therefore, as you might expect and, as you will see as this review progresses, the body is not entirely helpless in dealing with these radiation induced free radicals as some alarmists have suggested.  In contrast, as noted by Shirazi et al (1) the reactive oxygen species (ROS) induced by radiation also induce defensive enzyme production:

“ROS can induce the cellular antioxidant defense enzymes such as superoxide dismutase and glutathione peroxidase.”

Given that much of the impact of the nutrients I will be discussing is related not only to quenching of ROS but induction of the defensive enzymes mentioned in the above quote, I will discuss these enzymes in much more detail later.

Next, Shirazi et al (1) go into more detail as to what specifically happens when free radicals interact with living tissue:

“Reactive oxygen species (ROS) and free radicals induced by partial reduction of oxygen (O2) react with cellular macromolecules (i.e., nucleic acids, lipids, proteins, and carbohydrates) and damage them.  Major biomarkers of oxidative damage to living cells are (i) lipid peroxidation (LPO) products, comprising  volatile hydrocarbons measurable in exhaled air, such as ethane and pentane, and isoprostanes and aldehydic products measurable in tissues and body fluids; (ii) DNA hydroxylation products (e.g., 8-hydroxy-2′-deoxyguanosine (8-OHdG) and microscopic indices of damage such as chromosomal aberrations and micronuclei; and (iii) protein hydroxylation products such as oxidized amino acids.”

While all of the information in the above quote is, in my opinion, important to note, perhaps the key word clinically is “measurable.”  As you will see, laboratory tests are readily available that measure certain lipid peroxidation products and the DNA-hydroxylation product, 8-OHdG.  Therefore, by using these tests we can help address one of the greatest fears that our patients experience in relation to radiation, the fear of future declines in health due to current radiation exposures.  Specifically, these tests will enable us to show patients that we can quantify the effects of radiation exposure before any signs or symptoms are evident, thus giving us an opportunity to institute lifestyle and supplemental programs that will help address future formation of these oxidation products before clinically evident tissue changes occur.

Next, Shirazi et al (1) go into more detail on the specific cellular components that are affected by ionizing radiation.  As you might expect, given the very justifiable and well known fears about radiation and cancer, the most important cellular component to consider is DNA:

“Radiobiologists have long recognized that the most critical target of ionizing radiation passing through living tissues is the DNA (genetic material) that is present in the nucleus and mitochondria of most cells.  Exposure of cells to ionizing radiation results in immediate and widespread oxidative damages to DNA by both direct and indirect mechanisms.  About 60%-70% of cellular DNA damage produced by ionizing radiation is estimated to be caused by .OH, formed from the radiolysis of water.”

Next the authors point out that .OH can produce several different types of DNA oxidation products.  However, probably the most important, as suggested in the above quote where 8-OHdG was mentioned, is guanine:

“Among bases and, generally among nucleic acid components, guanine is the most susceptible DNA target for oxidative reactions mediated by .OH and other free radicals, and it exhibits the lowest ionization potential.  Thus, one of the most mutagenic lesions, and the most abundant lesion formed in irradiated chromatin is 8-hydroxyguanosine.”

However, are we defenseless against this effect of ionizing radiation?  As was seen above with the formation of antioxidant defense enzymes, the fortunate answer is “no”.  Shirazi et al (1) state the following about the formation of 8-hydroxyguanosine:

“Once formed, this product can be repaired by several mechanisms.”

Later in this series I will present much more information on DNA repair mechanisms and how they help protect us against the damaging effects of ionizing radiation.

As I mentioned, even more fortunate is the fact that we can measure levels of this key DNA oxidation component:

“Under laboratory conditions, one of the most common and abundant measurable oxidative DNA base adducts is 8-OHdG.  This is reported to be a key biomarker related to carcinogenesis.”

Nevertheless, even though 8-OHdG is a key biomarker related to carcinogenesis, it must be emphasized that carcinogenesis occurs only after DNA repair mechanisms have been overwhelmed:

“If DNA repair mechanisms, which are induced after exposure to ionizing radiation, are inefficient, the damaged DNA strands that are copied during replication lead to mutagenesis and carcinogenesis.”

Besides DNA, are other clinically important components of cells affected by ionizing radiation?  In the quote by Shirazi et al (1) it is noted that the answer to this question is yes.  However, another paper on melatonin and radiation that I will be reviewing in detail, “Antioxidative effects of melatonin in protection against cellular damage caused by ionizing radiation” by Karbownik and Reiter (2), makes it clear that key cellular components such as lipids and proteins are also profoundly affected.  The authors state:

“Radiation injury to living cells is, to a large extent, due to oxidative stress.  Reactive oxygen species (ROS) and free radicals induced by partial reduction of oxygen (O2) react with other cellular macromolecules (i.e., nucleic acids, lipids, proteins, and carbohydrates) and damage them.”

Because of the popular belief that radiation causes ill-health almost exclusively due to its affect on DNA, I feel that it is extremely important to fully appreciate what is stated in the above quote.  In the following quote Karbownik and Reiter (2) expand upon this key concept:

“The interaction of ionizing radiation with living cells induces a variety of reaction products and a complex chain reaction in which many macromolecules and their degradation products may participate.  The assumption that destructive processes initiated by ionizing radiation begin exclusively in a single subcellular organelle is questionable.”

As clinical nutritionists, why is it important that we fully appreciate this important distinction?  As noted above by Shirazi et al (1), ionizing radiation can create different oxidation byproducts depending on which cellular constituent is involved.  Furthermore, as you will see, these different oxidation byproducts are addressed by the body with different coping mechanisms that range from simple nutrients such as vitamin C and E to complex enzymes such as superoxide dismutase and catalase.  Because of this, the approach often used by many clinical nutritionists of employing a single, all purpose, highly marketable, easy to sell “wonder nutrient” to deal with the effects of ionizing radiation, whether it is melatonin, vitamin C, vitamin E, resveratrol, acai, etc., is totally inappropriate if optimal metabolic protection is our top priority.  As you might expect, as this series progresses, I will feature papers that highlight many of these nutrients in relation to ionizing radiation.  Since many of these papers tend to use language that suggests “panacea,” my understanding of the “big picture” is that this is surely not the case.  My understanding is that nutritional antioxidants and factors that support production and activity of endogenous antioxidants function optimally when provided together in a complementary fashion.  This could not be truer than when we consider the idea of using clinical nutrition to reduce the adverse impact of ionizing radiation on human health.

What is the consequence from a cellular standpoint when free radicals induced by ionizing radiation attack lipids and proteins?  Karbownik and Reiter (3) state:

“Besides DNA, lipids and proteins are also attacked by free radicals induced by ionizing radiation.  The initiated chain reaction caused by ionizing radiation leads to the formation of a variety of degradation products in biological membranes including products of lipid breakdown.  These degradation products induce changes in membrane structure and function that are exaggerated by the accumulation of free radical-mutilated proteins.  These degradation products make membranes more rigid (less fluid) and furthermore, after they migrate out of the membrane, they react with proteins and nucleic acids, thereby contributing to DNA damage and mutagenesis.  Significant changes in structure and function of membranes result in cell death via apoptosis.”

Fortunately, as I suggested above, we can gain information about membrane damage from ionizing radiation by measuring markers of lipid damage.  The authors point out:

“Another commonly measured parameter of lipid damage after ionizing radiation exposure is thiobarbituric acid reactive substances (TBARS).  These products, which include malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA), result from the interaction of free radicals with polyunsaturated fatty acids (PUFA).”

Several of the major functional medicine labs offer testing for MDA using urine as an analyte.

Ionizing radiation and hormesis: The dose does matter

Before leaving this paper, I would like to review a portion that expands upon the quote above from the Shirazi et al (1) paper that pointed out the ability of ROS to induce production of cellular antioxidant enzymes.  As you will see from the following quote from the Karbownik and Reiter paper (2), even an entity as destructive as ionizing radiation has a hormetic aspect to it that indicates certain doses can have a potentially positive impact on cellular function:

“…a substantial body of data provides evidence for a protective action of ionizing radiation when applied in low doses.  Ionizing radiation at low levels brings about what are referred to as adaptive responses and the stimulation of protective physiological mechanisms.  These adaptive responses are specific for doses typically below 0.5 Gy (gray).  The antioxidant properties of ionizing radiation at low doses as well as the protective effects of pretreatment with low-dose ionizing radiation against the damaging effects of high doses have been observed in a variety of studies using different parameters of oxidative damage (e.g., chromosome aberrations and micronuclei formation in human blood lymphocytes) and the level of lipid peroxides (LPO) and the activities of antioxidant enzymes.”

With the information contained in the above quote in mind, the authors arrive at a very compelling and controversial conclusion:

“Thus, the effects of low-dose ionizing radiation are similar to those brought about by antioxidants.”

Specifically, what dose of ionizing radiation compares to antioxidant protection?  Karbownik and Reiter (2) note:

“Interestingly, in a comparative study on ionizing radiation at a 50cGy dose and the antioxidant melatonin, these factors reveal a similar protective action against chemically induced LPO in mouse brain.”

The paper by Prasad entitled “Rationale for using multiple antioxidants in protecting humans against low doses of ionizing radiation” (4) provides another perspective on the concept of hormesis as it applies to ionizing radiation:

“‘Radiation hormesis’ is the name given to the putative stimulatory/adaptive effects of low level ionizing radiation generally in the range of 1-50 cGy of low-linear energy transfer (LET) radiation.  It should be noted that adaptive responses are commonly observed with tissue injuries irrespective of the source of the insult.”

Of course, I realize that the above statements could be interpreted as suggesting low levels of ionizing radiation have a beneficial effect on human health.  As noted by Prasad (4) this is not the case.  In contrast, it is a statement, albeit an important one, that certain doses of ionizing radiation induce very effective protective responses by the body:

“…ionizing radiation is a potent mutagen and carcinogen, and radiation-induced adaptive responses do not reflect the mutagenic changes that might occur after exposure.  Therefore, adaptive responses based on certain biological criteria following exposure to low doses of radiation cannot be considered beneficial to humans.  On the contrary, they simply reflect that cells have been exposed to injurious agents and that attempts are being made to repair some of the damage.”

As suggested in this quote and as I will point out in much more detail later, our bodies possess a highly sophisticated adaptive response to ionizing radiation that is amazingly effective in dealing with most of the ionizing radiation we encounter on a routine basis in our everyday lives.  However, because of the lifestyle choices made by many in this country, this adaptive response does not always function at peak effectiveness.  This is where we as clinical nutritionists can play a vital role.  Given that this adaptive response, like so many other physiologic processes, relies heavily on optimal intake of key nutrients, a large body of research that I will be presenting suggests that we can assist in the optimization of this adaptive response to better cope with whatever is coming in the months and years ahead in relation to environmental sources of ionizing radiation.

Two final thoughts on this important issue of ionizing radiation dose.  First, many of the more lurid and fear-inducing articles appearing in the mass media since March 11 point out that ionizing radiation from Japan is heading our way.  Of course, as we have all seen, these types of pronouncements have had predictable results on the psyche of much of the American population.  However, again I want to emphasize that many radiation experts point out that the key issue is not that radiation is coming, per se, but how much is coming.  Therefore, if we can play a role in educating the public about this very important aspect of ionizing radiation and its impact on health, thus markedly reducing fear, we will have played a role that I feel is just as important as educating the public about clinical nutrition.

Second, since this crisis began, one of the most confusing aspects for me has been the many different units of measurement of ionizing radiation and how much of each is a legitimate threat to human health.  Therefore, in the next section I will go into detail on the units of measurement of ionizing radiation. Then, as this series progresses, I will review some papers that go into great detail on the relationship between ionizing radiation and its impact on human health, with emphasis on the aspect of health that most of us have the greatest concern, cancer incidence.  Then, with this basic information in mind, I will examine the latest information available to me on the different amounts that are coming out of Japan and provide some hypotheses as to how these exposures might affect human health in the United States, particularly in relation to the large body of research I will be reviewing on how lifestyle optimization through diet and supplements can have an impact on these effects.

RADIATION UNITS OF MEASUREMENT

As I hope I have made clear in the review and discussion above, knowledge of dose levels is critical to having any comprehension of true risk to human health.  Unfortunately, gaining dosing knowledge about the Japanese nuclear reactor crisis has been greatly hampered by the fact that there are so many different units of measurement being mentioned in various media reports.  How do they compare to each other and what do they truly mean in terms of the sources of radiation exposure about which we are all familiar such as diagnostic imaging and airport security scanners?  To answer these questions I will first review some papers I found on the Internet that define the different units of measurement both in terms of what they suggest and how they relate to each other.  Then, I will discuss some papers that provide information on the level of radiation we typically experience with daily living in the US and how they compare to what is currently coming from Japan.

On the US Nuclear Regulatory Commission website I obtained a paper entitled “Measuring Radiation.”  To help readers understand how radiation is measured and the corresponding units of measurement, the mnemonic “R-E-A-D” is used.  The following is a description from the paper of what “R-E-A-D” means:

Radioactivity refers to the amount of ionizing radiation released by a material.  Whether it emits alpha or beta particles, gamma rays, x-rays, or neutrons, a quantity of radioactive material is expressed in terms of its radioactivity (or simply its activity), which represents how many atoms in the material decay in a given time period.  The units of measure for radioactivity are the curie (Ci) and Becquerel (Bq).

Exposure describes the amount of radiation traveling through the air.  Many radiation monitors measure exposure.  The units for exposure are the roentgen (R) and coulomb/kilogram (C/kg).

Absorbed dose describes the amount of radiation absorbed by an object or person (that is, the amount of energy that radioactive sources deposit in materials through which they pass).  The units for absorbed dose are the radiation absorbed dose (rad) and gray (Gy).

Dose equivalent (or effective dose) combines the amount of radiation absorbed and the medical effects of that type of radiation.  For beta and gamma radiation, the dose equivalent is the same as the absorbed dose.  By contrast, the dose equivalent is larger than the absorbed dose for alpha and neutron radiation, because these types of radiation are more damaging to the human body.  Units for dose equivalent are the roentgen equivalent man (rem) and sievert (Sv), and biological dose equivalents are commonly measured in 1/1000th of a rem (known as a millirem or mrem).”

How do roentgens, rads and rems compare?  The paper states:

“For practical purposes, 1 roentgen (R) = 1 rad (absorbed dose) = 1 rem or 1000 mrem (dose equivalent).”

The next quote gives some idea of why we need all these different forms of measurement:

“Note that a measure given in curie (Ci) tells the radioactivity of a substance, while a measure in rem (or mrem) tells the amount of energy that a radioactive source deposits in living tissue.”

If this seems complicated to you, you are not alone.  As someone who has little familiarity with the science of radiation, I had to read the above quotes several times before I could even begin to understand the differences between the different forms of measurement.  Of course, as you can see, the fact that, within each category, there are two different units of measurement only adds to the complexity.  Therefore, to understand how the different units of measurement in each category compare to each other, I would like to provide some information from the website “Steve Quayle’s Radiation Measurement Conversion Tables.”

R (Radioactivity)

1 microcurie = 37 kilobecquerel

E (Exposure)

1 roentgen = 258 microcoulomb/kg

A (Absorbed dose)

1 rad = 10 milligray

D (Dose equivalent or effective dose)

1 rem = 10 millisievert

Now I would like to present a statement from the US NRC paper that gives some idea of how these units of measurement apply to everyday sources of radiation exposure:

“…a person would receive a dose equivalent of 1 mrem from any one of the following activities:

3 days of living in Atlanta

2 days of living in Denver

1 year of watching television (on average)

1 year of wearing a watch with a luminous dial

1 coast-to-coast airline flight

1 year of living next door to a normally operating nuclear power plant.”

As those of you who have been following the many media reports on the Japanese nuclear disaster, the unit of measurement very often discussed is the microsievert.  The website ivpressonline.com provides some radiation measurements in microsieverts of common occurrences in the US:

“Limit on whole-body exposure for a radiation worker for one year: 50,000 microsieverts.

One year’s worth of exposure to natural radiation from soil, cosmic rays and other sources: 3,000 microsieverts

One chest X-ray: 100 microsieverts

One dental X-ray: 40-150 microsieverts

One mammogram: 700 microsieverts

CT scan (abdomen): 8,000 microsieverts

Full-body airport X-ray scanner: 0.0148 microsieverts

Airplane flight from New York to Los Angeles: 30-40 microsieverts

Smoking a pack a day for one year: 80,000 microsieverts”

What about not so common occurrences such as nuclear power plant accidents?  Consider the following:

“Average dose to people living within 10 miles of 1979 Three Mile Island Accident: 80 microsieverts

Average radiation dose of evacuees from areas highly contaminated by the Chernobyl disaster: 33,000 microsieverts (Of 600,000 of the most-affected people, cancer went up by a few percentage points – perhaps eventually representing an extra 4,000 fatal cancers on top of the 100,000 fatal cancers otherwise expected.)”

Thus, as I hope you can see, any discussion on radiation without mentioning amounts has little meaning.  In turn, media pronouncements boldly pointing out that “the radiation is coming!!” does more to instill over reaction, fear and panic than provide the knowledge that is so critical to reducing fear and leading us to the best responses that are only derived from calm and rationale contemplation and decision making.

In part II of this series I will begin with a discussion of the radiation amounts that have been suggested in the media to be coming from the damaged nuclear reactors.  Then, as I mentioned above, I will go into much more detail on the impact of radiation on human health, with a focus on cancer.

Moss Nutrition Report #238 – 04/01/2011 – PDF Version

REFERENCES

  1. Shirazi A et al. A radiobiological review on melatonin: a novel radioprotector. J. Radiat. Res. 2007;48(4):263-272.
  2. Karbownik M & Reiter RJ. Antioxidative effects of melatonin in protection against cellular damage caused by ionizing radiation. P.S.E.B.M. 2000;225:9-22.
  3. Karbownik M et al. Comparison of potential protective effects of melatonin, indole-3-proprionic acid, and propylthiouracil against lipid peroxidation caused by potassium bromate in the thyroid gland. J Cell Biochem. 2005;95(1):131-8.
  4. Prasad KN. Rationale for using multiple antioxidants in protecting humans against low doses of ionizing radiation. Br J Radiology. 2005;78:485-492.