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

It has now been approximately two months since I wrote part I of this series and, thanks to William and Kate, Osama Bin Ladin, Arnold Schwarzenegger, Maria Shriver, Harold Camping (Google this name if you do not recognize it), and, most recently, Anthony Weiner and a whole host of other headline grabbers, the Japanese earthquake of March 11, 2011 and the tsunami that followed have virtually disappeared from the front pages of newspapers and newsmagazines, plus the home pages of all the Internet news reporting sites that continue to proliferate.  Why do I say “thanks?”  While fortunes and misfortunes of people like William and Kate and Anthony Weiner respectively in no way diminish the horrors of 3/11/11 and our need for concern, they have, probably for reasons that have more to do with diversion than anything else, taken us away from the sense of national hysteria that permeated our lives virtually anytime our lives intersected with printed or electronic media during the days that immediately followed the disaster.  More importantly, the behavior and attitudes of many in response to the release of radiation from the Fukushima Daiichi Nuclear Power Plant, that has been considered somewhat irrational in some circles, seems to have given way to a sense of calm and detachment that comes with the realization that the horrors of that day are not going to lead to calamities on par with Chernobyl and atomic bomb blasts.

Therefore, now that we can be fairly confident that the world will not end soon, whether it is due to ionizing radiation or anything else, I would like to continue my review and commentary on ionizing radiation by providing an update on various measurements of radiation that relate to the Fukushima Daiichi Nuclear Power Plant disaster.  The most recent data I could find comes from a report entitled Fukushima Nuclear Accident Update Log: Updates of 4 – 11 May 2011 that was released by the International Atomic Energy Agency (IAEA.org).


Before I provide the various measurements listed in the IAEA report, given the confusion over the significance of the various units of measurement employed by those in the nuclear power industry, you may want to take a look at the end of part I of this series where I highlighted this issue (The newsletter can be found on our website, https://mnlibrary.blog/2018/07/17/a-perspective-on-ionizing-radiation-exposure-after-the-japanese-wake-up-call-part-i/).  With this information in mind, please note the following quote from the IAEA report that provides radiation readings for iodine and cesium throughout Japan, which is geographically divided into “prefectures”:

“The daily monitoring of the deposition of caesium and iodine radionuclides for 47 prefectures is continuing.  For the period of 5 – 10 May, deposition of I-131 was detected in three prefectures, with values ranging from 1.5 Bq/m2 to 4.5 Bq/m2.  Deposition of Cs-137 was detected in eight prefectures in the same period, the values reported ranging from 3 Bq/m2 to 44 Bq/m2.  The reported values show that variable but low deposition of radionuclides was still occurring in some prefectures.

As you may know, potassium iodide is only effective for reducing the negative impact of I-131.  It has no impact on the effects of Cs-137 (A more thorough discussion of the use of potassium iodide as a protection from the effects of ionizing radiation will follow later in this series).  In addition, recall that a Becquerel (Bq) is a measurement of the amount of ionizing radiation released by a material.  Of course, as I pointed out in part I of this series, the unit of measurement that is considered to be most important from a health standpoint is the one that relates to the amount of radiation absorbed and the medical impact of that absorbed radiation, the micro- or millisievert.  In relationship to this measurement, the IAEA report provides measurements for all 47 prefectures in Japan and areas more than 30 km from the Fukushima plant.  First, concerning all 47 prefectures, the report states the following:

“Gamma dose rates are measured daily in all 47 prefectures.  On 10 May the value of gamma dose rate reported for the Fukushima prefecture was 1.7 µSv/h.  In all other prefectures, reported gamma dose rates were below 0.1 µSv/h with a general decreasing trend.”

The following was reported for areas more than 30 km from the Fukushima plant:

“Gamma dose rates reported specifically for the monitoring points in the eastern part of Fukushima prefecture, for distances of more than 30 km from the Fukushima Daiichi plant, showed a general decreasing trend, ranging from 0.1 µSv/h to 20.3 µSv/h, as reported for 10 May.”

As noted in part I of this series:

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

With the above in mind, is 1.7 µSv/h significant from a health standpoint, let alone 20.3 µSv/h?  1.7 µSv/h converts to just under 15,000 microsieverts per year.  Therefore, for many areas of Japan radiation from the damaged nuclear plant is a major concern.  However, 0.1 µSv/h converts to 876 microsieverts per year.  While this amount warrants our concern, given that our exposure from natural sources is 3,000 microsieverts per year, it needs to be kept in perspective in terms of genuine clinical significance, particularly since we can assume with great probability that levels in the United States derived from the Fukushima plant will always be less than what is measured in Japan.  Of course, the customary response to the above statement has been that any amount, no matter how small, is a genuine health concern.  But is it really?  Later in this series I will present some very compelling research on “radiation hormesis,” which suggests that the above dictum is not absolute fact but a commonly held assumption that may differ greatly from reality.  Again, much more on this compelling controversy later.

Next, the IAEA report provides air concentrations of radionuclides at the Fukushima plant:

“On-site measurements at the west gate of the Fukushima Daiichi plant indicate the presence of I-131 and Cs-137 in the air in the close vicinity of the plant (within approximately 1km).  The concentrations in air reported for 10 May were 4 Bq/m3 for total I-131 and 16 Bq/m3 for total Cs-137.  The values observed in the previous days show daily fluctuations with an overall decreasing tendency.”

This, of course, represents more evidence that the radiation levels in the immediate vicinity of the power plant are still a major concern.  What about radiation levels in the food supply?  The IAEA report states:

“In Fukushima prefecture, levels in 212 (93%) of the 228 samples reported were below the regulation values for I-131 and radioactive caesium.  However, 16 of the 228 samples (7%) exceeded the regulation values set by the Japanese  authorities for Cs-134/Cs-137, including bamboo shoots (eight samples), shiitake mushrooms (four samples), ostrich fern (two samples), turnip (one sample) and sand lance fish (one sample).”

Thus, even in the area immediately surrounding the Fukushima plant, contamination of food with ionizing radiation, while a concern, is not at levels that create a crisis situation.

The last section of this report that I would like to highlight involves seawater contamination:

“The activity concentrations of I-131, Cs-134, and Cs-137 in seawater close to the Fukushima Daiichi plant at the screen of Unit 2 have been measured every day since 2 April.  Concentrations of Cs-134 and Cs-137 decreased from initial values of more than 100 MBq/L to less than 10 kBq/L on 30 April and have remained constant at this level to the present.

Levels of I-131 on 7 May remained at around 200 Bq/L”

Based on this report, I feel that it is safe to conclude that, at this point, ionizing radiation coming from the Fukushima Daiichi Nuclear Power Plant continues to be a concern from a short and long term perspective not only in Japan but worldwide.  However, I also feel it can also be concluded that the level of the risk is very far from crisis proportions, making impulse, panic-driven actions such as mass purchasing and mass consumption of potassium iodine not only ill-advised but, for many people, a greater risk to health than that presented by the radiation.  Therefore, given the current level of risk, I feel the best course of action is to take the time to educate ourselves so that we can rationally and leisurely create a plan of action that we can use to protect ourselves from the most probable worse case scenario, very low level, long-term exposure via air, water, and food.  It is my hope that this series will serve as an integral part of this educational process.


Now that I have given a more precise definition of the current magnitude of the risk from an exposure standpoint, I would like to discuss the main concern expressed by many if not most people.  What impact does any level of exposure have on human health?  As suggested above, we often think of the health risks of nuclear power plant accidents solely in terms of worse case scenario, which certainly explains the mass panic and hysteria that seems to inevitably follow even minor incidents such as that which occurred at Three Mile Island.  However, is what truly happens consistent with what most people think of in terms of worst-case scenario?  To answer this question I would like to present an excellent, recently published review of the literature entitled “Short-term and long-term health risks of nuclear-power-plant accidents” by Christodouleas et al (1)

The first important point that I would like to highlight from this paper makes it clear that the true worst case scenario of nuclear power plant accidents does not conform to the vision of many if not most people in this country:

“Of note, the explosions that have been seen in reactor accidents are not the same as those seen after the detonation of a nuclear weapon, since the latter requires highly enriched uranium or plutonium isotopes in concentrations and configurations that are not present in power plants.”

Next, I would like to highlight the section of the paper that describes the types of radiation exposure that occur with reactor accidents.  Christodouleas et al (1) discuss three types:

“Human radiation exposure as a result of reactor accidents is generally characterized in three ways: total or partial body exposure as a result of close proximity to a radiation source, external contamination, and internal contamination.  All three types can affect a given person in a radiation accident.  Total or partial body exposure occurs when an external source irradiates the body either superficially to the skin or deeply into internal organs, with the depth depending on the type and energy of the radiation involved.  For example, beta radiation travels only a short distance in tissue, depending on its energy, and can be a significant source of dose to skin.  High-energy gamma radiation, however, can penetrate deeply.  In previous reactor accidents, only plant workers and emergency personnel who were involved in the aftermath had substantial total or partial body exposure.”

Next, the authors discuss external contamination:

“External contamination occurs when the fission products settle on human beings, thereby exposing skin or internal organs.  Populations living near a reactor accident may be advised to remain indoors for a period to minimize the risk of external contamination.”

Finally, internal contamination is discussed:

“Internal contamination occurs when fission products are ingested or inhaled or enter the body through open wounds.  This is the primary mechanism through which large populations around a reactor accident can be exposed to radiation.  After Chernobyl, approximately 5 million people in the region may have had excess radiation exposure, primarily through internal contamination.”

What radioisotopes are released from nuclear reactor accidents?  The chart below from the paper notes those radioisotopes that were released during the Chernobyl accident: (Please download PDF version of this report to obtain the chart.)

What is the health risk of each of these radioisotopes?  Christodouleas et al (1) comment:

“The health threat from each radioisotope depends on an assortment of factors.  Radioisotopes with a very short half-life (e.g., 67 hours for molybdenum-99) or a very long half-life (e.g., 24,400 years for plutonium -239), those that are gaseous (e.g., xenon-133), and those that are not released in substantial quantities (e.g., plutonium-238) do not cause substantial internal or external contamination in reactor accidents.”

As was mentioned above, the primary risk that we are experiencing in the United States from the Fukushima Daiichi power plant accident relates to internal and external contamination.  Therefore, most of the radioisotopes that were released from the accident pose little threat.  However, as we all know, iodine-131 is a notable exception, as noted by the authors:

“In contrast, iodine-131 can be an important source of morbidity because of its prevalence in reactor discharges and its tendency to settle on the ground.  When iodine-131 is released, it can be inhaled or consumed after it enters the food chain, primarily through contaminated fruits, vegetables, milk, and groundwater.  Once it enters the body, iodine-131 rapidly accumulates in the thyroid gland, where it can be a source of substantial doses of beta radiation.”

Clinical consequences of radiation exposure

Specifically, what does radiation do to our bodies?  Christodouleas et al (1) point out:

“At a molecular level, the primary consequence of radiation exposure is DNA damage.  This damage will be fully repaired or innocuous or will result in dysfunction, carcinogenesis, or cell death.”

Before continuing, please note again that detrimental effects on human health are not inevitable with radiation exposure.  In contrast, as I have been suggesting, our bodies possess reparative mechanisms and coping strategies such as those that involve endogenous and exogenous antioxidants.  Therefore, a negative impact on health is far from a foregone conclusion.  In fact, as I have also been suggesting, the concept of “radiation hormesis” hypothesizes that certain levels of radiation are beneficial because they do much more to optimize reparative mechanisms and coping strategies than they act to create damage.  More on that later.

The authors then discuss the variables involved in determining whether any particular radiation exposure will be detrimental to health:

“The clinical effect of radiation exposure will depend on numerous variables, including the type of exposure (total or partial body exposure vs. internal or external contamination), the type of tissue exposed (tissue that is sensitive to radiation vs. tissue that is insensitive), the type of radiation (e.g., gamma vs. beta), the depth of penetration of radiation in the body (low vs. high energy), the total absorbed dose, and the period over which the dose is absorbed (dose rate).  The type of radiation and the dose rates that are involved in a reactor accident would typically be very different from those seen in the detonation of a nuclear bomb, which is why the biologic consequences of these events may differ substantially.”

Measuring radiation exposure

As I have mentioned, how radiation is measured can be as confusing as it is important when determining radiation exposure health risks.  What follows is a variation on what I have already provided in terms of units of measurement:

“The literature on radiation refers to dose in terms of both gray (Gy), the unit measurement for the absorbed dose, and sievert (Sv), the unit of measurement for the effective dose, which is the absorbed dose multiplied by factors accounting for the biologic effect of different types of radiation and the radiation sensitivities of different tissues.  1 Gy equals 1 Sv.”

Next, the authors provide a very informative chart similar to what I presented in part I of this series that shows estimated effective doses related to common medical and non-medical activities.  In addition, this chart contains a very helpful feature that I did not provide previously, comparative effective doses that came from the Three Mile Island and Chernobyl accidents.  This chart can be seen on page 7.

Acute radiation sickness

In the next section of the paper, Christodouleas et al (1) discuss acute radiation sickness.  However, since it is my assumption that virtually all of the readers of this monograph are not experiencing acute radiation sickness as the result of exposure to the Fukushima Daiichi accident, I will only briefly review this information.  One interesting point presented is the single dose level that is required to cause acute radiation sickness:

“When most or all of the human body is exposed to a single dose of more than 1 Gy of radiation, acute radiation sickness can occur.”

Interestingly, though, the authors are quick to point out that, in terms of acute radiation sickness in the general population, there are no recorded cases that have occurred as the result of a nuclear reactor accident.  Instead, all recorded cases, of which there are over 800, are related to medical procedures.  No acute radiation sickness occurred in the general population at Chernobyl:

“All 134 patients with confirmed acute radiation sickness at Chernobyl were either plant workers or members of the emergency response team.”

What about Three Mile Island?

“No confirmed diagnoses of acute radiation sickness were noted in workers or in the general population at Three Mile Island.”

What is the clinical presentation of acute radiation sickness?  The following quote presents a basic overview based on the experiences at Chernobyl:

“Much of the short-term morbidity and mortality associated with a high total or near-total body dose is due to hematologic, gastrointestinal, or cutaneous sequelae.  In the Chernobyl accident, all 134 patients with acute radiation sickness had bone marrow suppression, 19 had widespread radiation dermatitis, and 15 had severe gastrointestinal complications.  Hematologic and gastrointestinal complications are common because bone marrow and intestinal epithelium are especially radiosensitive as a result of their high intrinsic replication rate.  Cutaneous toxic effects are common because external low-energy gamma radiation and beta radiation are chiefly absorbed in the skin.  In Chernobyl, estimated skin doses in some patients were 10 to 30 times the bone marrow doses.  If total body doses are extremely high (>20 Gy), severe acute neurovascular compromise can occur.  At Chernobyl, the highest absorbed dose in a worker was 16 Gy.”

Health impact of chronic, low grade exposure

Of course, as I mentioned, there is no indication that any of the above will even come close to occurring in the United States as the result of events occurring at the Fukushima Daiichi power plant.  Therefore, the next section of the paper, which discusses long-term cancer risks as the result of exposure to I-131 and radioactive cesium, is much more pertinent to possible risks that people in the far-east and, to a certain extent, people in North America might conceivably experience.  Of course, the aftermath at Chernobyl provides the best information of potential outcomes in this instance:

“In the region around Chernobyl, more than 5 million people may have been exposed to excess radiation, mainly through contamination by iodine-131 and cesium isotopes.  Although exposure to nuclear-reactor fallout does not cause acute sickness, it may elevate long term cancer risks.

However, in terms of cancer risk, as I mentioned, exposure to nuclear reactor accidents is very different than exposure to an atomic bomb:

“Studies of the Japanese atomic-bomb survivors showed clearly elevated rates of leukemia and solid cancers, even at relatively low total body doses.  However, there are important differences between the type of radiation and dose rate associated with atomic-bomb exposure and those associated with a reactor accident.  These differences may explain why studies evaluating leukemia and nonthyroid solid cancers have not shown consistently elevated risks in the regions around Chernobyl.”

Of course, as most of you probably know, experiences relating to I-131 exposure and thyroid cancer represent a marked contrast to what was stated in the above quote, most especially in children:

“However, there is strong evidence of an increased rate of secondary thyroid cancers among children who have ingested iodine-131.  Careful studies of children living near the Chernobyl plant (which included estimates of the thyroid radiation dose) suggest that the risk of thyroid cancer increased by a factor of 2 to 5 per 1 Gy or thyroid dose.”

Interestingly, other factors were also associated with increases in thyroid cancer of children exposed to Chernobyl radioactive fallout:

“Factors that increase the carcinogenic effect of iodine-131 include a young age and iodine deficiency at the time of exposure.  Among children in regions with endemic iodine deficiency, the risk of thyroid cancer per 1 Gy or thyroid dose was two to three times that among children in regions in which iodine intake was normal.  Moreover, the risk of thyroid cancer among children who were given stable iodine after the Chernobyl accident was one third that among children who did not receive iodine.”

Before continuing with this review, I would like to comment on a very clinically relevant point presented in the above quote that I feel has been grossly under appreciated in all the discussion and fear that occurred in the aftermath of the Fukushima Daiichi accident.  Of course, we are all aware of the use of potassium iodide supplementation preventively to reduce risk of I-131 induced thyroid cancer.  However, I feel an important corollary to this use of potassium iodide on a pharmaceutical basis is the fact that iodine is also an essential nutrient to human health.  In turn, iodine deficiency is also an independent risk factor for thyroid cancer as the result of I-131 exposure.  Therefore, when considering preventive measures to protect patients from thyroid damage due to I-131 exposure, we need to go beyond the reflexive, often fear-induced urge to stock up on bottles of potassium iodide.  We must also inquire about patients’ lifestyle and eating habits so as to determine whether pre-existing iodine deficiency exists.  If this deficiency exists, along with dietary changes, supplementation of iodine should be instituted no matter what the chances are of I-131 exposure.  If deficiency is present, what dosage levels of supplemental iodine are optimal?  Based on my literature review that can be found in my iodine newsletter series*, effective and safe doses range from 150 mcg per day to 1-2 mg per day.  If pre-existing thyroid dysfunction can be demonstrated, though, it might be wise to start with lower doses.  However, in healthy individuals with no known thyroid dysfunction, doses of 1-2 mg per day will be very effective in correcting deficiencies with little to no risk of adverse reactions.

Christodouleas et al (1) next suggest some other preventive measures to minimize risk of I-131 induced thyroid dysfunction:

“In accidents in which iodine-131 is released, persons in affected areas should attempt to minimize their consumption of locally grown produce and groundwater.  However, since the half-life of iodine-131 is only 8 days, these local resources should not contain substantial amounts of iodine-131 after 2 to 3 months.”

Next, the authors provide more detailed information on proper use of potassium iodide supplementation when significant levels of I-131 contamination have been proven to exist:

“On the advice of public health officials, area residents may take potassium iodide to block the uptake of iodine-131 in the thyroid.  To be most effective, prophylactic administration of potassium iodide should occur before or within a few hours after iodine-131 exposure.  The administration of the drug more than a day after exposure probably has limited effect, unless additional or continuing exposure is expected.  Although potassium iodide can have toxic effects, the Polish experience with en masse administration of the drug after Chernobyl was reassuring.  More than 10 million children and adolescents in Poland were given a single dose of prophylactic potassium iodide, with very limited morbidity.”

Before continuing, I would like to address two somewhat controversial points in the above quote.  First, concerning the timing of potassium iodide supplementation in terms of effectiveness, other research that I will present in future segments of this series, suggest that supplementation can be effective even when given beyond a few hours after exposure, as suggested above.  Second, concerning side effects of potassium iodide supplementation, please keep in mind that the above quote refers to children only, who (according to research I will present) may have very likely been experiencing pre-existing iodine deficiency.  As many of you know, there is a great deal of controversy about what dose of iodine will induce iodine related side effects.  Most of this controversy, as reported in my iodine newsletter series*, revolves around adults suffering from chronic illness who, based on conventional standards of optimal iodine levels, may have no pre-existing deficiencies prior to iodine supplementation.  Therefore, I feel we cannot automatically extrapolate safety data on children who may be iodine deficient to chronically ill adults who may have no pre-existing deficiency.


Hopefully, this overview presentation, combined with what I presented in part I, has given a good sense of the realities of radiation exposures ranging from nuclear power plant disasters to everyday occurrences.  For, as I have suggested, the biggest inducer of fear, panic, and inappropriate action is ignorance.  While I do not want to suggest that the Fukushima Daiichi power plant disaster is totally benign in relationship to residents of North America, I would like to suggest that, mainly due to ignorance of the realities of radiation exposure and the fear that inevitably results, many statements were made about risks to North Americans that appeared to many, including me, to have no rational basis.  Again, it is my hope that my efforts so far in this series will not only educate but help replace the feeling of fear that was so prevalent in the few days that followed March 11 with a sense of calm that comes with knowledge.

In part III of this series I will present published literature that goes into much more detail on the realities of I-131 exposure from both atomic bombs the Chernobyl disaster.  In addition, I will present much more literature on what is certainly the biggest, most fear-inducing controversy of all among those living in the United States and their response to the events of March 11, the need for potassium iodide supplementation and, if it is necessary, ideal doses.  (Please download PDF version of this report to obtain the chart.)

* If you are interested in reading my Iodine newsletter series, please visit our website www.mossnutrition.com/newsletters  At Search Newsletter Achive, type in keyword “High Dose Iodine” and check off the box for MNR, then search.  It will return 20 newsletters, including the 12 newsletters in the Iodine series that spans from 4/1/2007 to 8/1/2009: # 214, #214, #216,#217, #218, #219, #220, #221, #222, #227, #228. Or, please call our office and request a print copy of the “Iodine Series Newsletters – 12 issues” and we will gladly send you a set.

Moss Nutrition Report #239 – 06/01/2011 – PDF Version


  1. Christodouleas JP et al. Short-term and long-term health risks of nuclear-power-plant accidents. N Eng J Med. 2011;Published online April 20, 2011.