Geiger Counter Numbers, How Bad is Bad?
Given the recent events in Japan and the nuclear reactor damage and radiation entering the atmosphere there, the following information may help to understand the units of measurement being discussed, and how it may correlate to Geiger Counter readings such as those being displayed around the country on the Radiation Network.
Units of Measurement (Radiation)
1 rad = 0.01 gray (Gy)
1 rem = 0.01 sievert (Sv)
1 gray (Gy) = 100 rad
1 sievert (Sv) = 100 rem
Rad and Gray are ‘absorbed dose’ units.
Rem and Sievert are ‘equivalent dose’ units.
Why a Rem and a Sievert?
They relate to biological damage done to human tissue and factor the differences between types of radiation. A multiplication factor is used that represents the ‘effective’ biological damage of a given type of radiation. This is the main reason for these units – to factor the differences in damage that is caused from one type of radiation to the next.
Radiation Factor (QF Quality Factor)
(1) Beta
(1) Gamma
(1) X-ray
(10) Nuetron
(20) Alpha
For example, the list above shows that a ‘rad’ or ‘gray’ unit of ‘Alpha’ energy that is absorbed by soft human tissue does 20 times more damage than a ‘rad’ or ‘gray’ of Gamma, X-ray or Beta radiation.
Measuring Radiation with a Geiger Counter CPM
What is CPM (also the ‘number’ used on the Radiation Network )?
CPM (counts per minute) is a measure of radioactivity, a unit of measurement for a Geiger counter. Technically, “It is the number of atoms in a given quantity of radioactive material that are detected to have decayed in one minute.”
Most Geiger counters are calibrated to Cs137 (Cesium).
1,200 CPM on the meter (for Cs137) is about 1 mR/hr (milliRad per hour).
120 CPM on the meter (for Cs137) is about 1 uSv/hr (microSievert per hour).
How many CPM of radiation is bad?
Answer: It depends on how long you are exposed at any given level. The Radiation Network website, for example, uses a threshold warning level of 100 CPM, mainly because it is unusual to observe levels of 100 or higher without something more going on in the area than just background level.
Having said that, how could one figure out the ‘badness’ of a given level? How bad is bad? All we need to do is put in terms that makes sense.
First, we must understand a few radiation facts and numbers regarding dosage. There tend to be lots of conversions and it can be confusing, but by plodding through the math, you can determine a better idea and relationship of the Geiger counter numbers versus the risks to your health.
Radiation Dosage
Radiation dosage is a measure of the risk of biological harm that the tissues receive in the body.
The unit of absorbed radiation dose is the sievert (Sv). Since one sievert is a large quantity, radiation doses normally encountered are expressed in milliSievert (mSv) or microSievert (µSv) which are one-thousandth or one millionth of a sievert. For example, one chest X-ray will give about 0.2 mSv of radiation dose.
On average, our annual radiation exposure due to all natural sources is about 300 milliRem, which is equivalent to 3 milliSieverts (3 mSv). Adding man-made sources (medical procedures, and others) the average annual U.S. radiation dose is about 600 milliRem, which is equivalent to 6 milliSieverts (6 mSv).
Average annual human exposure to radiation (U.S.)
600 milliRem (mRem)
6 milliSievert (mSv)
Radiation dose for increase cancer risk of 1 in a 1,000
1,250 milliRem (mRem)
12.5 milliSievert (mSv)
Earliest onset of radiation sickness
75,000 milliRem (mRem)
750 milliSievert (mSv)
Onset of radiation poisoning
300,000 milliRem (mRem)
3,000 milliSievert (mSv)
Expected 50% death from radiation
400,000 milliRem (mRem)
4,000 milliSievert (mSv)
What do the Radiation Network CPM numbers mean with regards to health risk?
With the examples of radiation dose listed above, we can correlate how long it would take to experience those effects based on a hypothetical Geiger counter CPM number.
So, let’s use the number 100, since this is the threshold that the Radiation Network website has chosen. The Cs137 calibration factor listed above (120 CPM) was converted to obtain the proper factored results listed below (0.83x). Higher CPM numbers are also listed for relevancy.
Days compared with the avg. annual human exposure (U.S.)
207 (at 100 CPM)
42 (at 500 CPM)
14 (at 1,500 CPM)
2 (at 10,000 CPM)
Days to receive dose for increase cancer risk of 1 in a 1,000
432 (at 100 CPM)
86 (at 500 CPM)
28 (at 1,500 CPM)
4 (at 10,000 CPM)
Days for earliest onset of radiation sickness
25,937 (at 100 CPM)
5,187 (at 500 CPM)
1,729 (at 1,500 CPM)
259 (at 10,000 CPM)
Conclusion: Regarding the radioactive fallout from Japan reaching here to the U.S., the metered Geiger Counter CPM that we see on the Radiation Network can be compared to the equivalent ‘what-IF’ scenarios listed above. Not saying though that anything less would not be ‘bad’ for us, there are lots of theories out there regarding long-term effects of various types of radioactive ionized particles making it into the food chain, etc…
Interesting fact:
All food sources combined, expose a person to around 40 millirems per year on average.
Many foods are naturally radioactive, and bananas are particularly so, due to the radioactive potassium-40 they contain. The equivalent dose for 365 bananas (one per day for a year) is 3.6 millirems (36 μSv).
Other foods that have above-average levels are potatoes, kidney beans, nuts (especially brazil nuts), and sunflower seeds.
Ways to limit radiation exposure:
1. Time (limit exposure time)
2. Distance (intensity decreases sharply according to the inverse-square-law)
3. Shielding
(alpha: nearly anything… a sheet of paper will stop it)
(beta: wood, water, plastic-acrylic, aluminum)
(gamma: water, concrete, lead)
Disclaimer: Do not rely upon this information for life or health, it is only one person’s estimation based on a several hours research and punching calculator buttons. We have no affiliation with the Radiation Network, who may or may not agree with these numbers.
If you enjoyed this, or topics of preparedness or current events risk awareness, consider our survival blog RSS feed, new posts by E-mail, or bookmark us at Modern Survival Blog
So, we have radiation level readings, but is there any way to get readings on WHAT is coming over here? Do we know if its Iodine or Cesium or Plutonium? Seems like that’s more important than the levels themselves…
@Gelaine, Although apparently currently very low readings, we might expect to see Iodine-131, Cesium-137, and possibly Plutonium-239, based on the fuel that had been used in Fukushima. Again, emphasis currently on the very low traces, which are evidently representative of the fact that what we are seeing now is the very beginnings of what happened at Fukushima during Day 1. We’ll see if and how much the levels rise next week to reflect what has happened there during this week. I think we’re OK for now.
Do you still “think we’re ok”? Almost all States have had sustained CPM’s of just the CS-137 of 50 or above. I presume that any raised CPM is bad & that averaging doesn’t matter, since this stuff is coming to rest upon the ground, buildings & cars. Isn’t my presumption correct, because none of these “items” fully deplete in less than a month & no-one’s decontaminating or even testing their water, food, shoes, pets, playing fields, streets, sidewalks, stores, offices, houses or cars. I conclude that everyone has already blown through their typical 600mrem & even their harmful 1200mrem by now. What are your reactions to the reported increase in birth mortalities & alarming findings in food, water & milk…at this late date & after my above possibly flawed reasoning.
Yes. Depleted uranium or “DU” as they refer to it in military circles. According to a UC Davis study U-238/PU-238 uranium buckyballs were formed when the cold sea/fresh water was used to cool down the molten rods at Fukushima. The water then travels out to sea, many tons of it per day carrying these microscopic “buckyballs.” They travel fast and do not easily break down. They also aerosolize into the atmosphere and winds from whitecaps and wave breaking action along the shoreline. These buckyballs, primarily U-238, can cause all manner of cancers, genetic corruption and massive numbers of birth defects . . . DESPITE the element not giving off too much radiation, per se. It’s not the radiation we’re concerned about relative to the buckyballs. It’s the element, itself . . . The birth defects and the high numbers of veterans on disability from the Gulf War and Iraqi Freedom are almost identical as a result of their exposure to depleted uranium or “DU.” The birth defects taking place in Iraq, such as Basra, are massive as a result of the use of DU in Iraq, as well. The Obama Administration is simply denying anything’s wrong, increasing the level of radiation considered dangerous and denying funding to detect and measure the levels of buckyballs in a given area/region. Same old stuff: Moving the goalposts, again . . . and preventing discovery by preventing the means to discovery. Therefore, in their reasoning, these concerns don’t exist. It’s that simple. I’m wondering if the author of this website, which I greatly appreciate, is basing his data as to what is and is not deleterious/dangerous based on standards set forth by the Federal government BEFORE or AFTER the Obama Administration simply resorted to semantics (typical of lawyers) to skew the interpretation of what the radiation levels mean. I want you to see this: http://thewe.cc/weplanet/news/depleted_uranium_iraq_afghanistan_balkans.html
Great information Ken! Thank you!
In general Iodine and Cesium are the natural byproducts of the breakdown of the radioactive fuel. The reactor normally creates these byproducts by the billions of atoms a second So to the extent that radioactive material is “released” it will most generally be in the form of Iodine-131 and Cesium-137. If there is an explosion (steam or hydrogen) then the fuel itself is “disturbed” and could be released as well. Then it is possible that you would get plutonium or uranium released. Thankfully this fallout is usually of atom sized particles and this distribute and dilutes the risk. The bigger risk is if larger “clumps” of material are released but because of their size these particles tend to drop out very close to the source. Some of the “fallout” will be other ionized “stuff”. This could be small particles of concrete, dirt, building materials, almost anything. The risk from these particles is extremely low. By it’s nature the most likely “stuff” to travel any distance will be the least dangerous to life.
The EPA’s website (http://www.epa.gov/japan2011/) shows the GAMMA GROSS COUNT RATE (CPM) in Anaheim to be in the 3000 range. Why is this so much higher than the alert level you discuss which is 100 CPM?
@Jack, you need to look at this one: “Beta Gross Count Rate (CPM): 17″, which is near the top of the list for each station. All of the others, range 2 through 10, mean other things having to do with the isotopes themselves. The ‘range’ numbers are to be interpreted differently.
Thank-you for this article. Could you give a reference for the increase in cancer rates related to radiation?
@Luanne, There are a multitude of sources available by doing a Google search
Lots of various opinions about thresholds, etc…
I’m interested in further understanding the level of MOX plutonium headed here and how to logically respond to it.
How does the radiation fallout or the worst-case scenario at the Fukushima nuclear plant compare with the fallout that resulted from US nuclear-bomb tests in the Marshall Islands?
Does anyone have an idea?
I was considering to start collecting antique vaseline (uranium) glass. However, after reading this page, and looking at some Geiger counter measurements on the following site, I am having second thoughts about this hobby!
http://1st-glass.1st-things.com/vaselineglass.html
Although most vaseline glass sites maintain that it is perfectly safe (unless ground and ingested), I have my doubts. A drinking glass generating 24000 CPM does not sound very healthy to me!
I really appreciate the efforts by Modern Survival Blog to carefully risks.
Keep in mind please that these risk levels explained above reflect external exposure to radiation and do not address what happens when radionuclides lodge inside the body after being inhaled or ingested.
As Helen Caldicott tells us, one atom of plutonium could kill over time if lodged in the body near vulnerable tissues.
Also, the body mistakes radioactive iodine for the stable form and essentially sucks it up in the thyroid.
Strontium is confused with calcium and is embedded in bones.
Furthermore, Chris Busby and others have documented very thoroughly that the risk model explained so carefully above is flawed (no discredit to the very helpful efforts above)and lacks predictive value.
An account of the model’s limitations can be found here
http://majiasblog.blogspot.com/2011/08/short-history-of-risk-assessments-for.html
the article one sees showing the limitations of the standard model of assessment of radiation danger is very brief and makes one simple, albeit telling, point — that busby points out that the physicist approach was used, reducing the human being to a model of a bag of water of the same weight and shape, then seeing how that reacted to radiation. that is very helpful, in general, but then what are the detailed results of correcting the analytic viewpoint to taking into account a more complex, filled-out model of a human exposed to radiation? how does that model revise the figures given in the original article for danger levels? the blog does not address these important questions.
I have measured my Ipad1 and found 2x background readings. See a confirmation here:
http://www.youtube.com/watch?v=LT6qHaKFgGY
Could this be of concern for a heavy user?
Gary Ehlenberger
Retired Staff Scientist, Motorola
i work in a nuclear medicine department where everyday im exposed to radiation. when i give injections im exposing myself to technetium 99m and a count in the 10′s of thousands per second. my annual dose is around 2500 mSv. my odds of developing cancer from it are no higher than the general public. people just seem to have an unnecessary fear of radiation.
also when majia said 1 atom of plutonium can kill…. one atom of plutonium can only decay once. in nuclear medicine we give a dose of one Gigabecquerel to a patient for a bone scan (giving off many thousand of cpm from many thousand of technetium atoms decaying)…this gets taken up in bones when its labelled to MDP and will stay in their body irradiating them for a few days…it carries no real risk or we wouldn’t do it.
@anon; Well, if you follow your proper protocols you aren’t exposed to anything near what the pts are exposed to. And while I will agree that in the context of the “good derived form the diagnostic ability” of the scan, there is still SOME residual effect that has significant statistical meaning for health to the pts. No radiation is good radiation, pun intended, period. One “speck” of plutonium (not an atom) is, if inhaled, pretty much a death sentence, don’t split hairs. Yes, you give doses in the Gigabecquerel ranges, but the half life isn’t measured in years or decades much less centuries as fallout and contamination is. It does carry risk for the pts, regardless of what you say/think. Just sayin’. Also, fyi, Nuke techs do suffer from a ‘statistically higher” rate of leukemia and skin cancer, along with radiologists that do a “lot of fluoro” than other radiological technologists, also just sayin’. Are you new to this career field? Worked there for over 20 years. You should check with your radiation monitor for more in depth information about the effects of your “nuclear medicine” on people, so you understand what you are doing. Survive well. enjoy.
Links and numbers would be useful here.
I think you meant to say 2500 micro SV not Millsievert as 250 millisievert is 250 Rem which is 50 times the legally allowable annual maximum for a radiation worker
I have done extensive research on this subject and I would have to say that I don’t think alpha particles are the most damaging. I thought that alpha particles were the LEAST dangerous kind and that neutrons were able to pass through a metre of concrete and cause extensive damage to human tissue
If this isn’t true. Why?
The real reason for breaking radiation down to hundreds of new names is simply to confuse the layman and muddle the facts. This allows the polluters a smoke screen to hide behind and geiger counter businesses to pop up everywhere. What we really know is all radiation is dangerous to breath and eat. It is really measured in amount of exposure per hour. Total dose per year, if exceeded increases your chances of cancer. What we also know OS there are still Hiroshima survivors living today. We know age has a lot to do with it. The young people up to their 40s are in danger. Older than that uptake is limited because our body’s slow down. We live on a radioactive planet get used to it.
Can anyone answer a question for me. I have a CD-700 and I get 50 clicks per minute, when it clicks it will move the needle half way up the meter scale set on times one. I do believe this is a gamma click. How can I find the gamma ray particle. and how dangerous is this…
Oh yes I forgot to mention this is in a building outside of the building I get zero counts per minute. Could this be a particle from Fukushima in the duct work ?