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.

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.

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 this 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.

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).

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 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)

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.

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UPDATE: New Maps; Radiation in Perspective; Tokyo Faces Fallout; US Under Threat; Live Gieger Counter; Financial Panic

UPDATE: March 15, 2011 11:45 CST

…Japanese stock market down 2000 points in less than a week.

…World financial markets in panic – commodities, stocks, precious metals all down significantly in single day trading

…situation in Japan is escalating

…Over half a million evacuated. Prime Minister of Japan urges residents within 19 miles of reactors to flee or bug in

…Princeton Physicist: “It’s way past Three Mile Island already.”

…Tokyo radiation levels rising (200 miles from reactor site)… Live Geiger Counter

…Radiation levels around Japanese cities in real time (Link) *Note, due to an extremely large volume of traffic, this web site may not be accessible.*

…Secondary source: Latest real-time radiation level screen capture (source):

…While earlier posted fallout map showed innaccurate “RAD” level count, wind patterns remain intact… Radiation set to cross Pacific

…Nuclear Regulatory Commission spokesman David McIntyre: “Right now it’s quite possible that there could be some radiation floating over the United States“

…Radiation threatens California agricultural region (Map)

…Perspective on Radiation Levels:

Here’s a chart showing the range of radiation levels in milli sieverts (mSv). Currently up to 400mSv per hour are being recorded in the immediate vicinity of Fukushima. Remember, although these figures may suggest that the level of radiation being recorded at Fukushima is not extremely high, the danger is constant exposure over a period of time. For this reason, people within the 20km evacuation zone are at high risk of serious harm.

7,000-10,000mSv – Person dies from radiation poisoning. (Full body exposure).
1,000mSv – Nausea and vomiting (Full body exposure).
500mSv – Decrease of lymphocytes in peripheral blood (white blood cells that defend your body) (Full body exposure).
200mSv – No clinical conditions confirmed below this number
10mSv – 1 year’s worth of natural radiation (Brazil)
6.9mSv – CT scan
2.4mSv – 1 year’s worth of natural radiation (world average)
1mSv – Limit of one’s year’s exposure to non-natural radiation (excluding medical examinations)
0.6mSv – Stomach X-ray
0.2mSv – A return air trip from Tokyo to New York
0.05mSv – Chest X-ray (or the level of radiation expected around a nuclear power plant – in practice it is much lower than this)

…more updates to come as information becomes available

UPDATE: March 12, 2011 15:30 CST

…Japanese officials say nuclear disaster averted; but new reactor is now in danger

…Millions currently without power, gas

…Report from Mito, Japan:

In Mito, another town in the area, long lines formed outside a damaged supermarket as hundreds waited for medicine, water and other supplies. Supplies ran low as people stocked up, not knowing how long it would take for fresh goods to arrive.

“All the shops are closed, this is one of the few still open. So I came to buy and stock up on diapers, drinking water and food,” Kunio Iwatsuki, 68, told Reuters.

…Tour of grocery store in earthquake/Tsunami stricken area – Shelves just about empty:

…Grocery store in Tokyo – supplies of basic goods, non-perishables dwindling:

UPDATE: March 12, 2011 12:06 CST

…Status of nuclear plant is unconfirmed… Reports vary… some suggest plant has melted down… others suggest plant is intact

…Tens of thousands missing in Japan

…Thousands being evacuated in potential nuke fallout zone… 12 mile radius

…Explosion in building housing reactors (video)

…Chernobyl-like meltdown possible (video)

…Fuel rods may have melted

…West coast residents on alert in the event of a nuclear meltdown

…Wind may carry radiation across Pacific to West coast of North America…. 180 Hour Wind Forecast Model

…Unofficial fallout map (Note that this map has not yet been legitimately sourced, thus the estimated “Rad” levels are as of yet unconfirmed, though the wind patterns match those of the 180 hour forecast above):

***This Nuclear Fallout Map below has been identified as a hoax. As mentioned in our original posting, the source was not confirmed. We chose to publish this map to demonstrate the fallout pattern in the event high levels of radiation were released in Japan. ****

…As of yet, the estimates for radiation release levels in the event of meltdown as measured in Rads/Greys is unknown, therefore Rem/Microrem biologically effective doses cannot be measured accurately…

…radiation level outside the reactor became elevated to 1,015 microsievert—the equivalent of being exposed to the maximum allowable level for a full year in a single day. The level has since come down sharply.

…Survival / Alternative News forums go ballistic

…General Radiation Absorption ESTIMATES (source):

0-50 rads – No obvious short-term effects
80-120 rads – You have a 10% chance of vomiting and experiencing nausia for a few days
130 -170 rads – You have a 25% chance of vomiting and contracting other symptoms
180-220 rads – You have a 50% chance of vomiting and having other severe physical effects
270-330 rads – 20% chance of death in 6 weeks, or you will recover in a few months.
400-500 rads – 50% chance of death
550-750 rads – Nausia within a few hours ; no survivors
Greater than 1000 rads – immediate incapacitation and death within a week or less.

…Japanese emergency officials are planning to distribute iodine to those in nuclear radiation zones:

Japanese authorities are making plans to distribute stable iodine, a treatment to prevent radiation poisoning, to residents near two damaged nuclear plants, the International Atomic Energy Agency says.

…FDA has historically recommended Potassium Iodide (KI) within 3 – 4 hours of radiation exposure

…Retail provider of KI

…Related SHTFplan articles:

The Effects of Nuclear Weapons

Survive Anything: Nuclear Attack

UPDATE: March 11, 2011 19:45 CST

…88,000 Reported Missing, Hundreds dead

UPDATE: March 11, 2011 17:00 CST

…California: 1 Confirmed Dead, 2 Swept out to sea as they watched incoming Tsunami

…Oregon: 4 Swept out to sea, rescued by Coast Guard

UPDATE: March 11, 2011 16:30 CST

…Reports that Fukushima nuclear reactor is at 2.1 times normal pressure

…Radiation reportedly at 1000 times normal and rising; no evacuations of plant or surrounding areas as of yet.

The following just released video from PBS Newshour documents just how powerful the Japanese Tsunami was. It completely demolishes an entire village in under a minute:

The Sakurajima Volcano on Southern Tip of Japan has begun erupting:

ORIGINAL STORY POSTED March 11, 2011 09:00 CST:

…An estimated 8.9 magnitude earthquake off the east coast of Japan sent Tsunamis across the Pacific, striking Japan with waves reportedly as high as 33 feet.

…Other Southeast nations have also been struck.

…Hawaii was inundated with a Tsunami earlier this morning.

…Oregon closes schools…California on alert…expect waves potentially as high as 5 feet around 11am EST

…Canada on alert

Videos from Japan

Massive Tsunami wave races inland…tons of debris…burning fires atop waves…boats, cars, buildings uprooted:

Tsunami overwhelms Japan port city:

Tsunami causes whirpool:

Japan Tsunami: Cars, Debris thrown around by water like children’s toys:

Tsunami Reaches Hawaii:

Wave’s reportedly not unusually high. Officials warn waves may get as high as 6 feet:

The scene at a local grocery store in Hawaii as residents anticipate the Tsunami:

Tsunami in Open Sea – Headed towards other south east Asian countries…Almost all of Pacific Basin on alert:

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