Putting Radiation Exposure in Context

March 26th, 2011
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There has been a lot of talk about radiation exposure levels in Japan, both to workers and the general public.
This chart on radiation exposure as a factor of banana consumption from xkcd has been making the rounds and does help with understanding a lot.

The following is intended to provide a more in-depth and technical primer on the issue of radiation and health effects.

Measuring Radiation Exposure:

Exposure to ionizing radiation is commonly measured in total cumulative dose. Exposure can occur through a number of different paths. It can come from an external source, such as a gamma emitting isotope, from an internal source, such as inhaled or ingested radioisotopes or from a combination of the two. The path of exposure along with the type of radiation (alpha, beta, gamma or neutron) as well as the energy level of the radiation will all affect what biological effect occurs.

In order to quantify the biological effects of radiation exposure, the rem (Roentgen equivalent man) was created. Rems are a weighted to approximate the total biological effect on a human of radiation exposure, which can through either contact, proximity or internal exposure. Rems are also commonly expressed as the unit mrem (for millirem) or one thousandth of a rem.

In the late 1970′s, a new unit the sievert (abbreviated Sv) was created. The conversion from rems to sieverts is very straight forward. One sievert is equal to 100 rem. The sievert has been adopted as the Standard International unit for measurement of radiation dose, and is now considered the preferred unit for scientific settings. However, the rem also continues to be widely used.

Because the sievert is a very large unit of dosage it is very often expressed as milliseiverts or microseiverts.

Conversions (from Wikipedia)

* 1 rem = 0.01 Sv = 10 mSv
* 1 mrem = 0.00001 Sv = 0.01 mSv = 10 Î?Sv
* 1 Sv = 100 rem = 100,000 mrem (or millirem)
* 1 mSv = 100 mrem = 0.1 rem
* 1 Î?Sv = 0.1 mrem

“Dose rate” is another measure, commonly used for ambient radiation levels. It represents the dose a person will receive in a given amount of time. Thus if the dose rate is said to be 1 mSv/hr, then a person exposed for one hour would receive 1 mSv of radiation. However, this does not mean anyone exposed to such an intensity will have this dose. Being exposed to such a level for half an hour will result in only .5 mSv of radiation. If a dose rate this high only exists for a brief period of time, then the total exposure is a factor of how long the high rate occurs for.

For example, a dental X-ray head may produce radiation with the intensity of more than one Sv per hour, but it only is turned on for a fraction of a second. Therefore, knowing the peak dose rate tells you very little if the time is not given.

Personally, I like rems and millirems. Perhaps it’s because I’m American and thus I was brought up to think in screwy units. Thankfully, in this case, it’s easy to convert between the two, unlike pounds, feet and degrees Fahrenheit.

*In actuality, dose measurement is a bit more complex than this, because radiation doses can be measured as being full body dose, skin dose or the dose to a certain organ or region of the body. To keep things simple and because it applies to the circumstances of exposure from a reactor incident, this article is based on full body dose.

Average Annual Dosage:

Bellow Average: <3000 microsieverts (300 mrem)
Lifestyle: A person who happens to live in an area with very low geological radiation, does not live in a masonry building, does not visit masonry structures very often, does not fly or flies very infrequently and spends the majority of their time at a low altitude.

About Average: 3000-5000 microsieverts (300-500 mrem)
Lifestyle: Average. People who live in most parts of the United States, Europe, not very high above sea level,fly occasionally and have other moderate sources of exposure.

Above Average, but not abnormal: 5000-10,000 microsieverts (500-1000 mrem)
Lifestyle: A person who lives in a high altitude city such as Denver Colorado will receive about 400 microsieverts per year right off the bat. If they happen to live in a masonry structure, cook with natural gas or get a few dental x-rays, this will further increase their annual dose. An annual dose o 10,000 microsieverts is above what mot people get, but not unusual.

Moderately High: 10,000-25,0000 microsieverts (1000-2500 mrem)
Lifestyle: It is not typical to get this high an annul dose of radiation exclusively due to natural sources, but it is certainly possible. A few areas of the world have been found to have very high background levels which expose residents to such levels every year. It is also possible that a person’s radiation dose could be pushed up into this level if they required a few medical imaging procedures in a year.

High: >25,0000 microsieverts (>2500 mrem)
Lifestyle: Only on rare occasions would this level be the result of natural sources exclusively, this dose is routinely exceeded in a year by those who need multiple medical imaging procedures. Cancer treatment often results in doses many times higher than this.

Single Event Exposure:

(typical numbers. Actual dose may be slightly more or less)

Single Dental X-ray: 10 microsieverts (1 mrem)
Extremity X-ray (arm, leg): 10-30 microsieverts (1-3 mrem)
Single Skull X-ray:
80 microsieverts (8 mrem)
Single chest X-ray
: 10o microsieverts (10 mrem)
Thyroid scan:
14o microsieverts (14 mrem)
Mammogram Session:
400 microsieverts (40 mrem)
Hip/Pelvis X-ray: 650 microsieverts (65 mrem)
Lumbar Spinal X-ray: 1,200 microsieverts (120 mrem)
Head CT Scan: 2,000 microsieverts (200 mrem)
Upper GI X-ray: 2,250 microsieverts (225 mrem)
Barium Enema (full film series): 5,000 microsieverts (500 mrem)
Chest/Upper Torso CT Scan: 7000 microsieverts (700 mrem)
Abdominal/Pelvis CT Scan: 10,000 microsieverts (1000 mrem)
Full body CT Scan: 12,000 microsieverts (1200 mrem)
CT-Scan Heart Angiogram: 20,000 microsieverts (2000 mrem)

North American Coast to Coast Flight: 30 microsieverts (3 mrem)
Trans-Pacific flight: 50 microsieverts (5 mrem)
Extended Non-Stop flight (eg New York to Hong Kong): 80 microsieverts (8 mrem)
Long Distance Round Trip (eg. London to Sydney and Back): 200 microsieverts (20 mrem)

Radiation levels with acute symptoms (radiation poisoning)

No Acute Symptoms: <.5 Sieverts (<50 rem)

Symptoms: No observable acute symptoms. Possible slight change in blood at very high end of exposure, such as increased white blood cell count.
Time to onset: N/A
Treatment: There is very little active treatment required or possible at such low levels of exposure.
Mortality: Zero

Slight: .5-1 Sievert (50-100 rems)

Symptoms: Mild nausea, possible temporary headache, mild temporary fatigue. Many persons exposed to this level will show no acute symptoms at all. Possible slight increase in risk of some infections.
Time to onset: Several hours to about a day, if symptoms show up at all.
Treatment: Bed rest. Monitoring and observation. Providing fluids.
Mortality: Approximately zero. Otherwise healthy individuals are not in serious risk of death from this level of exposure. Possible complications in individuals with preexisting health conditions.

Slight: 1-2 Sievert (100-200 rem)

Symptoms: Mild to moderate nausea, possible temporary headache, temporary fatigue. Roughly half of individuals exposed to this level will show some signs of . Possible increase in risk of some infections.
Time to onset: A few hours.
Treatment: Bed rest. Monitoring and observation. Providing fluids. In some circumstances antibiotics may be used to reduce the risk of infection.
Mortality: Rare in healthy individuals. Possible complications in individuals with preexisting health conditions. Approximately zero expected deaths with medical intervention.

Moderate: 2-4 Sievert (200-400 rem)

Time to onset: An hour to a few hours.
Symptoms: Moderate to severe nausea, headache, fatigue, diarrhea, fever, possibility of infection. Possible damage to bone marrow ranging from mild to moderate in severity. Possible internal bleeding.
Treatment: Bed rest. Extended period of reduced exertion. Antibiotics. Monitoring for infection. Fever reducers. In some cases, medications are administered to increase the production of white blood cells. Transfusions of red blood cells and platelets may be called. Antibiotics
Mortality: This dose level is life threatening. Even healthy individuals may die within a week without medical intervention. With medical intervention, most otherwise healthy individuals will recover.

Severe: 4-6 Sievert (400-600 rem)

Symptoms: Severe nausea, vomiting, fatigue. Possible loss of consciousness. Significant damage to bone marrow. Bleeding, possibly severe in some cases. Skin ulcers. Organ failure.
Time to onset: Less than an hour.
Treatment: Intensive care. Antibiotics. Surgical or non-surgical intervention to stop bleeding. Blood transfusions. Possibly kidney dialysis or other treatments intended to aid in cases of organ failure. Bone marrow transplant.
Mortality: The prognosis at this level becomes poor. Even healthy individuals have a high probability of death. With medical intervention, the likelihood of survival is less than 50%.

Very Severe: 6-8 Sievert (600-800 rem)

Symptoms: Severe nausea, vomiting, fatigue. Possible loss of consciousness. Significant damage to bone marrow. Bleeding. Skin ulcers and sores. Organ failure.
Time to onset: Less than an hour, possibly as little as minutes.
Treatment: Same as above, but with additional focus on pain management, palliative and hospice care.
Mortality: The prognosis is grim. Although it is possible to survive this high a level of exposure, it’s unlikely. Even with medical intervention, only a small portion of those exposed to this level will survive over the long term.

Unsurvivable: 8+ Sieverts (800+ rem)

Symptoms: Severe nausea, incapacitation, severe internal bleeding, multiple organ failure. Death.
Time to onset: Immediate or nearly immediate.
Treatment: Pain management, palliative and hospice care.
Mortality: 100% Depending on the dose and circumstances, an individual exposed to high doses may survive for a period of a few days to more than a week, but ultimately medical intervention is unlikely to result in longer term survival.

Radiation and Cancer:

There exists considerable debate in the scientific and policy-making sector about the long term effects of low doses of radiation on the probability of developing cancer. There is no doubt that very high doses of ionizing radiation do indeed increase the probability of cancer, but for lower doses it is much harder to measure the effect. Since low levels of exposure would be expected to produce, at most, very low increases in the likelihood of cancer developing, measuring the effect in real world situations is extremely difficult, especially since cancer is already a fairly common condition, with more than one third of humans developing some form of cancer some time in their life.

Early on in the study of radiation and human health, the linear non-threshold hypothesis was formulated. LNT simply means that the impact of radiation on long term health, such as cancer rates, is always directly proportional to the dose and therefore can be extrapolated down to zero. For lack of good data for low dose rates, it was adopted as “worst case scenario” for most policy use.

As scientific data has accumulated, the validity of LNT has come into question. Despite large studies on both humans exposed to radiation and animals, empirical evidence of increases in cancer rates at low doses of radiation continues to be elusive and in some cases the data has been contrary. Studies of populations living in areas with high background radiation levels, such as Ramsar Iran, have found no increase in cancer rates but have found decreases.

Such data supports the concept of radiation hormesis, which holds that increased exposure to radiation up to a point actually decreases cancer rates. The mechanism for this is not entirely understood, but appears to be the stimulation of DNA-repairing enzyme mechanisms in cells. It may also be related to the increased destruction of cells with corrupted genetic material or to increased immune system activity.

Alternately, there is also the threshold model, which holds that radiation exposure has negligible effect, either good or bad, at very low doses.

This is made more complex by the fact that the impact of radiation on health is related to the dose distribution. A single large dose of a radiation having a greater effect than the same cumulative dose if distributed over a longer period of time.

The debate on LNT versus threshold models versus hormesis goes beyond the scope of this post, and the above information is meant only as a very basic primer.

However, if LNT is presumed to be true:

One rem of exposure (short period of time) = .08% increase in the likelihood of death from cancer
One sievet of exposure (short period of time) = 8% increase in the likelihood of death from cancer

One rem of exposure (cumulative, over about a year) = .04% increase in the likelihood of death from cancer
One sievet of exposure (cumulative, over about a year) = 4% increase in the likelihood of death from cancer
(source)

Per individual the risk would be considered higher for younger persons and lower for older, since they are not likely to live as long anyway and cancer does not develop right after radiation exposure occurs but some years later. Thus if a 90 year old person were exposed to a high dose of radiation, there’s a high likelihood that they would die of other natural causes before any radiation-induced cancer had a chance to develop. Because of this the above rates are based on a standard population.

Another way of looking at this is based on the average impact on a standard population per dose, where the number of the probability is expressed as the number of additional cancer cases expected per a given number of persons.

By this measure:

One rem of exposure = One additional cancer-related death per 1,250 individuals
One sievet of exposure = One additional cancer-related death per 12.5 individuals

One rem of exposure (cumulative, over about a year) = One additional cancer-related death per 2500 individuals
One sievet of exposure (cumulative, over about a year) = One additional cancer-related death per 25 individuals
(source)

In practice, this would mean that for every rem of exposure to a population of 10,000, there would be an increase in the number of individuals who ultimately die of cancer from about 2,000 to 2,008. (of course the number of 2,000 per 10,000 is very approximate, but it puts this in context.)

Yet another way of quantifying this risk is based on the impact it has on the average life expectancy of an individual in a population exposed to a given dose of radiation.

By this measure:

A person exposed to one additional rem per year for their entire adult life would have a reduced life expectancy of about 50 days.
A person exposed to one additional seivert per year* for their entire adult life would have a reduced life expectancy of 13.65 years.

*which is a real real lot to be exposed to EVERY YEAR!
(source, source)

BUT, IF LNT IS NOT TRUE (which it probably isn’t)

While this does mean that the probability of a small dose of radiation causing cancer is nill, it also means it is a lot more complicated to calculate the actual risk, since it becomes more than just multiplying. To make matters more complicated, there is likely a considerable difference depending on the dose distribution (whether it is all at once or over what period of time the dose occurs).

Current data indicates that the LNT model is not supported by single event dosages of 100 mSv (10 rem) or less or by chronic annual dose levels of 200 mSv (20 REM). Above such dose rates there do appear to be small increases in cancer, although the available data does not indicate that the relationship is linear until much higher doses occurs. At levels o more than half a sievert per event the relationship appears to be more or less linear.

Based on this data, it could be concluded that one time exposure to 100 mSv does not result in an increase in the probability of cancer and that doses of more than 100 mSv but less than 250 mSv may or may not result in a minuscule increase in lifetime cancer risk, depending on the circumstances, and in any event, should not be cause for excessive worry.

Other Health Effects

Aside from cancer, there are a number of other health conditions which are known to be related to exposure to ionizing radiation.

Cataracts – Acute exposure to one to two 1-2 sieverts (100-200 rem) to the eye region is associated with the formation of cataracts. If the exposure is over the course of a longer period of time, the total dose may need to be up to four times higher before cataract formation is detected.

Increased cataracts over the long term, as a result of chronic exposure to lower levels of radiation is less well understood, due in part to the fact that cataracts are common in older individuals to begin with. Current data indicates that only relatively high exposure to radiation is likely to cause cataracts.

Infertility – A dose of 150 mSv (15 rem) to the testies will reduce sperm production and potentially cause temporary infertility in males. This is not enough to cause any measurable long-term effect, however. A similar dose may result in a temporary reduction in egg viability in females. Single doses above one sievert (100 rem) may create longer term infertility. In general, permanent infertility as a result of radiation exposure would require a dose level that would normally be fatal, if the dose is distributed across the entire body. However, if the dose is focused on the gonadal region it is possible for a person to become completely infertile for life without receiving a full body dose sufficient to cause radiation poisoning.

Birth Defects – A single event dose of 250 mSv (25 rem) to a population is believed to result in a small increase in birth defects, although it is more likely to result in non-viable pregnancies than term births of individuals with major birth defects. This topic is so complicated and has so many qualifications that it needs an entire post to itself and really goes beyond the limits of this post.

Chronic gland problems – Radiation is known to cause damage to saliva glands, mucus glands and other glands in the body which can result in insufficient secretions, causing membranes to become dry or irritated. This effect is only seen at very high localized dose levels and is usually found in cancer patients who have received very intense radiation therapy to a local area of the body.

Hair Loss - Most often seen in cancer patients, this is caused by the fact that radiation tends to have a greater effect on fast growing cells, such as hair follicles. It is usually temporary. The effect only happens with very high doses of radiation and is not immediate. Being exposed to radiation will not make your hair suddenly start falling out in clumps.

Sources:
Radiation and Risk
Radiation Sickness – The Mayo Clinic
NRC Basic References
Typical Patient Exposure
Radiation Exposure: Facts Versus Fiction (University of Iowa)
ANS Dose Chart
An Introduction to Radiation Hormesis
Radiation Hormesis and the Linear-No-Threshold Assumption
Radiation Limits


This entry was posted on Saturday, March 26th, 2011 at 1:35 pm and is filed under Bad Science, Enviornment, Good Science, Misc, Nuclear. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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26 Responses to “Putting Radiation Exposure in Context”

  1. 1
    DV82XL Says:

    An excellent primer on the subject Steve, and it will serve as a great reference in the ongoing debate.


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  2. 2
    Jody Says:

    Steve, wow. Quite a nice bit of research. Even though you link to the chart at the top of the page, I think it would be great if you just listed the various rad releases from the Japan disaster at the bottom of the article. I don’t propose a discussion of those levels as it would be quite contentious. But it would put the radiation released from the reactors in further context.


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  3. 3
    drbuzz0 Says:

            Jody said:

    Steve, wow. Quite a nice bit of research. Even though you link to the chart at the top of the page, I think it would be great if you just listed the various rad releases from the Japan disaster at the bottom of the article. I don’t propose a discussion of those levels as it would be quite contentious. But it would put the radiation released from the reactors in further context.

    It’s a lot to keep track of, especially since new numbers are coming out all the time. Note that I have been a bit light on the posts recently. In part this is because I was working on this one. I figured better to put it out than to spend more time researching the confirmed releases and population dose.

    That may come in a subsequent post.


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  4. 4
    Anon Says:

    IIRC the highest dose anyone got at Fukushima Dai-ichi was 106.3 mSv to one of the workers who was in the Unit 1 containment.


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  5. 5
    Huw Jones Says:

    Great post, very informative.

    I’ve learned a lot about radiation since Fukushima, but I’m still confused about two things:

    Firstly, risk of radiation sickness and its associated symptoms seem to be a function of the dose magnitude and the time in which it is exposed to the individual. For example, I have heard radiotherapy exposes one to perhaps 20 Sv, but as it is spread over days and weeks, it is not in anyway fatal. Can you please elaborate on the dynamics of the function of time and dose?

    Secondly, I’ve heard that when radioactive material is inside the body, it is far more dangerous to the individual. To what extent is this true? The only information I can find is preaching by the Greenpriests.


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  6. 6
    drbuzz0 Says:

            Huw Jones said:

    Firstly, risk of radiation sickness and its associated symptoms seem to be a function of the dose magnitude and the time in which it is exposed to the individual. For example, I have heard radiotherapy exposes one to perhaps 20 Sv, but as it is spread over days and weeks, it is not in anyway fatal. Can you please elaborate on the dynamics of the function of time and dose?

    Are you talking about medical imaging or cancer treatment?

    20 Sv is a hell of a big dose for a person to get from imaging, even if they needed many CT scans.

    Cancer treatment can be high enough to the point where it does cause some level of radiation poisoning. Usually efforts are made to maintain the dose in as small an area as possible. Localized dose is different than full body dose. You could have several Sv targeted at a small area while the total body dose is still lower.

            Huw Jones said:

    Secondly, I’ve heard that when radioactive material is inside the body, it is far more dangerous to the individual. To what extent is this true? The only information I can find is preaching by the Greenpriests.

    I general yes, but it gets complicated because it depends on factors like how much of the substance stays in your body for how long versus whether you excrete it.

    Also depends on the type of isotope. Alpha emitters are basically harmless outside the body but if you ingest them and absorb them into your cells they will do more damage than gamma emitters. While gamma emissions are not necessarily that much worse if internal versus an external source.

    It gets complicated. Hence, people go to grad school and get PhD’s in this stuff. I didn’t. I’m only summarizing info out there. I’m not an expert. You’d probably need one for info related to all the nuances of internal dosimetry.


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  7. 7
    Zahir Hussain Says:

    Impressive and informative,
    Such information may be useful to non-radiation community, who can understand facts and myth of dose level at various stages. More over, this will encourage the participation of the people in good governance for better understanding of the radiation-risk-effects and benefits in the long term perspectives. This is the right posting in the right time.


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  8. 8
    Mark Says:

    Nice post indeed !

    Just remember folks that the unit of effective whole body dose (the Sv) has to be expressed as such to make sense (the media misses that as do many experts). You take the absorbed dose (Gy) and weight it by a radiation weighting factor – this gives you equivalent dose (in Sv) for a part of the body. You then take the equivalent dose (in Sv) and weight with a tissue weighting factor this gives you a Whole Body Effective Dose in Sv. Most of the lower doses expressed above are actually expressed as Whole Body Effective Dose. In this way they are not really ‘doses’ at all – these are expressions of risk. The ball park figure used at present by ICRP (with rounding and not accounting for age etc) is 5% per Sv.

    It is important to get a grip with the above so that you can then understand the effects of internally incorporated radioactive material. Radioactive materials taken into the body will, based on their chemical nature etc, be taken up by certain parts of the body. Therefore the dose delivered to that part of the body will be an Equivalent Dose ONLY. Once you have worked out what it is, you can then apply the above weighing method to turn that equivalent dose into a Whole Body Effective Dose. It does NOT mean that the whole body has somehow now received a dose everywhere. All it means is that the overall risk of cancer is the same as if the whole body HAD been uniformly irradiated. It then allows the comparisons to be made as shown above.

    I think the following two YouTube vids that I had produced explain the above well, and would also enhance the overall blog article.

    Radiation Dose Part 1
    http://tinyurl.com/3xkybt3

    Radiation Dose Part 2
    http://tinyurl.com/689ppap

    Finally, to complicate matters a little further, but this is still valuable to consider, there are two completely opposing views that one can see in the media at the moment. One reports that the risk from ionising radiation are massively underestimated (from internally incorporated radioactive material), the other reports that they are massively overestimated. For interested readers the following resources might be worth a look at:

    http://www.llrc.org (underestimated)
    http://www.radiationandreason.com (over estimated)

    For the record, I am probably somewhere between the two (just like ICRP…)


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  9. 9
    drbuzz0 Says:

    It can be very hard to make such complex concepts reasonably understandable by summarizing them down to their basics while at the same time keeping them accurate and not leaving out anything too important. Obviously this is not actually all the info and it’s vastly more complicated.

    The question one needs to keep asking is “How much of this does someone need to know to at least have the gist and not be flying blind?”


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  10. 10
    Mark Says:

            drbuzz0 said:

    It can be very hard to make such complex concepts reasonably understandable by summarizing them down to their basics while at the same time keeping them accurate and not leaving out anything too important.

    Obviously this is not actually all the info and it’s vastly more complicated.

    The question one needs to keep asking is “How much of this does someone need to know to at least have the gist and not be flying blind?”

    You are right of course. My comments above are not in any way criticising the detail or depth of your article – rather, if someone is interested they can go deeper if they wish! One problem I have in the media is the concept of 10* safe dose etc etc. If you believe in LNT there is no safe dose, just an acceptable level of risk (acceptable is built into ALARA – taking into account social and economic factors). However, I concede that the general public want to know ‘what safe is’.

    For example – there have been recent reports on two workers that got their feet burnt. For days there were reports of 100-180 mSv (sometimes a dose and sometimes expressed as a dose rate). I was quite certain all along that these doses were not related to the burns (not directly anyway). They might have been measurements above the contaminated water, they might have been gamma dose rates, they might have been Sr-90 BREM x-ray dose rates – but I was sure they were not related directly to the feet burns. However, by reading the reports as they were – it implied that this level of dose (or dose rate !!) could lead to hospital care and real injury.
    I am now hearing reports that the dose to the feet was 6-8 Sv – this is more like it. That would cause some degree of local burning (reddening of the skin would start to occur after about 3Sv). However, even that should really be expressed in Gy (or RADs !!) – it is a deterministic effect and completely far removed from the whole body dose concept in Sv that we are talking about. In this case the radiation and tissue weighting factors I discussed above are irrelevant since we are not talking about risk of cancer – only threshold effects.


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  11. 11
    Mike Says:

    So what level of exposure do you think the worst of the workers (besides the ones that were just plain vaporized in the explosion) received? I’ve read people skin basically just melted off (I think the medical term is “sloughing”). Which category would that fall under?


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  12. 12
    Mark Says:

            Mike said:

    So what level of exposure do you think the worst of the workers (besides the ones that were just plain vaporized in the explosion) received? I’ve read people skin basically just melted off (I think the medical term is “sloughing”). Which category would that fall under?

    Had not heard that… Nothing to do with ionising radiation in my view – sounds more like thermal radiation (e.g. super heated steam on exposed skin??)


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  13. 13
    Engineering Edgar Says:

            Mike said:

    So what level of exposure do you think the worst of the workers (besides the ones that were just plain vaporized in the explosion) received? I’ve read people skin basically just melted off (I think the medical term is “sloughing”). Which category would that fall under?

    did not know any workers were killed in the explosion (surely not vaporized). I had heard that at least four were taken to the hospital with injuries in the first blast and 11 in the second. Did any of them die since?

    The workers who got burns I think were not the same workers. They went into the reactor building without good wading boots and the water was too high. Their boots got filled up with water and the water apparently contained enough radioactivity to cause burns to the skin it was in contact with.

    So I am guessing, based on my limited knowledge of this, that they probably got a very high dose to their feet and lower legs and probably got a pretty low dose to the rest of their body.


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  14. 14
    TomT Says:

    One small spelling fix.

    BUT, IF LNT IS NOT TRUE (which is probably isn’t)

    Probably should read (which it probably isn’t)


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  15. 15
    Mike Says:

            Engineering Edgar said:

    did not know any workers were killed in the explosion (surely not vaporized).

    I had heard that at least four were taken to the hospital with injuries in the first blast and 11 in the second.

    Did any of them die since?

    The workers who got burns I think were not the same workers.

    They went into the reactor building without good wading boots and the water was too high. Their boots got filled up with water and the water apparently contained enough radioactivity to cause burns to the skin it was in contact with.

    So I am guessing, based on my limited knowledge of this, that they probably got a very high dose to their feet and lower legs and probably got a pretty low dose to the rest of their body.

    I was referring to the workers at Chernobyl, not Japan. There are pictures of people whose skin is literally peeling right off in layers at least an inch thick. It’s like one really really bad sunburn.


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  16. 16
    TomT Says:

            Huw Jones said:

    Firstly, risk of radiation sickness and its associated symptoms seem to be a function of the dose magnitude and the time in which it is exposed to the individual. For example, I have heard radiotherapy exposes one to perhaps 20 Sv, but as it is spread over days and weeks, it is not in anyway fatal. Can you please elaborate on the dynamics of the function of time and dose?

    Basically if you give the body time to heal between doses it will. Again there can be complicating factors but in general if you get a dose of radiation, such as radiotherapy, your body will heal from the damage the radiation does. Unless severe enough in the single dose it doesn’t permanently damage the body. Which is why radiotherapy treatments are spread out over time to give the body a chance to heal between doses. Same with chemotherapy, massive doses of highly toxic chemicals, you want a break between treatments. Because the treatments for both types have to be ongoing there remains some continuous repeated damage to the body from these treatments. Thus for example the gland damage exhibited by some patients who have had radiotherapy. Basically their suffer from some long term damage as a result of the body not having sufficient time to heal between doses.

    es not as strong, thus the increase in cancer from high dosage exposure, basically in that case the bo

    Secondly, I’ve heard that when radioactive material is inside the body, it is far more dangerous to the individual. To what extent is this true? The only information I can find is preaching by the Greenpriests.

    Hmm, sort of. It isn’t as cut and dried and is often claimed. Eating something actively emitting high levels of radiation is probably not a good thing. But if their claim was true people couldn’t eat banana’s, spinach, and a number of other normal everyday foods that contain natural radioactive materials.

    Thus my caveat about eating active high dose emitters. I wouldn’t want to eat uranium for example or cobolt 60 or oh plutonium, or any of a number of things. But this is different than eating something like the potassium-40 in bananas. You just are not going to get any damage from the dose you eat and frankly the body will get rid of the excess potassium like it does any other mineral.

    So your instinct is right, but like anything you can eat radioactive things that are bad for you. But them try drinking a few gallons of water in a couple hours or breathing pure oxygen for to long and learn about oxygen poisoning or water toxicity. Surprisingly just about anything can kill you if you eat it.


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  17. 17
    TomT Says:

    quote comment=”31857″]
    Firstly, risk of radiation sickness and its associated symptoms seem to be a function of the dose magnitude and the time in which it is exposed to the individual. For example, I have heard radiotherapy exposes one to perhaps 20 Sv, but as it is spread over days and weeks, it is not in anyway fatal. Can you please elaborate on the dynamics of the function of time and dose?

    Basically if you give the body time to heal between doses it will. Again there can be complicating factors but in general if you get a dose of radiation, such as radiotherapy, your body will heal from the damage the radiation does. Unless severe enough in the single dose it doesn’t permanently damage the body. Which is why radiotherapy treatments are spread out over time to give the body a chance to heal between doses. Same with chemotherapy, massive doses of highly toxic chemicals, you want a break between treatments. Because the treatments for both types have to be ongoing there remains some continuous repeated damage to the body from these treatments. Thus for example the gland damage exhibited by some patients who have had radiotherapy. Basically their suffer from some long term damage as a result of the body not having sufficient time to heal between doses.

    es not as strong, thus the increase in cancer from high dosage exposure, basically in that case the bo

    Secondly, I’ve heard that when radioactive material is inside the body, it is far more dangerous to the individual. To what extent is this true? The only information I can find is preaching by the Greenpriests.

    Hmm, sort of. It isn’t as cut and dried and is often claimed. Eating something actively emitting high levels of radiation is probably not a good thing. But if their claim was true people couldn’t eat banana’s, spinach, and a number of other normal everyday foods that contain natural radioactive materials.

    Thus my caveat about eating active high dose emitters. I wouldn’t want to eat uranium for example or cobolt 60 or oh plutonium, or any of a number of things. But this is different than eating something like the potassium-40 in bananas. You just are not going to get any damage from the dose you eat and frankly the body will get rid of the excess potassium like it does any other mineral.

    So your instinct is right, but like anything you can eat radioactive things that are bad for you. But them try drinking a few gallons of water in a couple hours or breathing pure oxygen for to long and learn about oxygen poisoning or water toxicity. Surprisingly just about anything can kill you if you eat it.


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  18. 18
    Matte Says:

            Mike said:

    I was referring to the workers at Chernobyl, not Japan. There are pictures of people whose skin is literally peeling right off in layers at least an inch thick. It’s like one really really bad sunburn.

    The skin is not an inch thick so that is a bogus statement, please reference.


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  19. 19
    Robert Sneddon Says:

    I dug through the pdf reports at the JIAF site with the day-to-day summaries of the situation at the Fukushima Daiichi reactors. As part of their reporting they usually list a radiation exposure reading. Unfortunately they don’t always use the same location for this part of the report, but the two most common points where measurements were made are called the Main Gate and the West Gate, which I presume are on the site boundaries. The West Gate readings at 19 March were 313uSv/h and by the 29th March they were down to 116 uSv/h. At the Main Gate early on 20 March the reading was 269uSv/h and the last reading reported was 170uSv/h at 11:00 on 26 March.

    They also list a reading for the Daini site which has four BWR-5 reactors, all of which are reported to be in shutdown. These reactors are a few kms across the bay from the Daiichi site. Those readings run from 15.9uSv/h on 17 March down to 6.2uSv/h on 29 March with one anomolous spike to 26uSv/h on 22 March. I guess that a lot of the radiation detected at this location is due to airborne crap from the damaged Daiichi reactor buildings across the bay.


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  20. 20
    Zeph Says:

    I appreciate the information, I’ve been wanting just this perspective.

    However, I noticed fairly substantial discrepancies between this article and the chart linked dfrom the article (http://xkcd.com/radiation/). For example,

    arm x-ray, xkcd: 1 uSv
    arm/leg x-ray, this article: 10-30 uSv

    chest x-ray, xkcd: 20 uSv
    chest x-ray, this article: 100 uSv

    (is the upper GI x-ray really 22 times the chest, or did the upper GI figure mean to refer to a CT scan?)

    This seems like more variance than the disclaimer “Actual dose may be slightly more or less” would lead one to expect.

    Is there some good explanation? It would be good to understand this to better than an order of magnitude error, before I promulgate it further.

    One good bit, if accurate. According to the xkcd chart, living in Denver only adds around 450 uSv per year.
    According to that source, the lowest annual dose which is clearly linked to an increased cancer risk is 100,000 uSv (100 mSv), over 200 times that amount. And here I’ve long heard that living at altitude carried some extra cancer risk; apparently not measurably so, if that source is credible.


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  21. 21
    drbuzz0 Says:

            Zeph said:

    I appreciate the information, I’ve been wanting just this perspective.

    However, I noticed fairly substantial discrepancies between this article and the chart linked dfrom the article (http://xkcd.com/radiation/). For example,

    arm x-ray, xkcd: 1 uSv
    arm/leg x-ray, this article: 10-30 uSv

    chest x-ray, xkcd: 20 uSv
    chest x-ray, this article: 100 uSv

    (is the upper GI x-ray really 22 times the chest, or did the upper GI figure mean to refer to a CT scan?)

    This seems like more variance than the disclaimer “Actual dose may be slightly more or less” would lead one to expect.

    Is there some good explanation? It would be good to understand this to better than an order of magnitude error, before I promulgate it further.

    I tried to come up with a reasonable representative dose for modern procedures you’d get and I tried to use several sources to verify it, but the variance is actually more than slight. I just didn’t want to go into that at depth, becasue that’s a whole other topic.

    But the factors that influence it include:

    The speed of the x-ray film.
    Whether it’s film or electronic.
    If electronic, whether it’s digita or the older analog image intensifier system.
    Whether it’s a single film plate or multiple films.
    Exactly what they are looking for (broken bone versus foreign body versus fluids etc)

    GI X-rays are rather involved. You have to swallow quite a bit of a special barium compound and then the actual procedure usually involves several x-rays which may have an extended exposure versus standard.

    In many circumstances, it’s actually done in real time with the x-ray being more like a movie than a photograph, as with a “barium swallow”

    http://www.youtube.com/watch?v=5QhBvXsJ53E


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  22. 22
    Robert Estrada Says:

    Dr. Buzzo,
    Yesterday I was listening to npr and they had a british environmentalist from the “guardian weekly?” on. His name was George M.. I am going slightly deaf and could not get his name but he was making a statment that the problems with the reactors in Japan had changed his mind about Nuclear power as the plants were not the latest safest design but they had survived a maximum earthquake and tsunami and so far theere have been no deaths. He then went on to make statements regarding the huge anual death toll from coal mining. When asked about the radiation contamination and environmental exposure he said something about the dangers posed to those living near coal fired plants and the vast tracts of the world distroyed by mining. I am assuming the greens will burn him in effigy but maybe some others will come to their senses also.
    Robert Estrada


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  23. 23
    Chem Geek Gregor Says:

    A very good primer on the basics!

    Personally, I like rems and millirems. Perhaps it’s because I’m American and thus I was brought up to think in screwy units. Thankfully, in this case, it’s easy to convert between the two, unlike pounds, feet and degrees Fahrenheit.

    Easy solution: Keep on using REM’s, but call them centisieverts. You will be correct, because one sievert = 100 rem, so one rem = 1 centasievert. An odd division (you hear the centi prefix mostly with meters and rarely with other units), but totally proper within SI context.


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  24. 24
    BMS Says:

    Another way for Americans to think of it is the following: sieverts are dollars, rems are pennies.

    Unfortunately, both sieverts and rems tend to be too large when discussing most dose levels. Another good rule-of-thumb conversion factor relies on the factor of ten:

    10 microSv = 1 millirem

    Then remember that natural background radiation is about 300 millirem or 3000 microSv, although it is not uncommon for background to be twice that much.


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  25. 25
    Ty Belnap Says:

    Good article, I have been in the Health Physics field for 35 yrs, consistent info with what I have studied.


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  26. 26
    Depleted Cranium » Blog Archive » Radiation Claims by US Sailors Says:

    […] More info on radiation levels and effects […]


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