What’s the radiation level right now?

March 19, 2011

Concerned about radiation from Japan?

It’s highly improbable that dangerous levels of radiation would drift more than a few miles from the damaged nuclear power plants in Japan, but maybe seeing some actual readings might convince people there’s not much to worry about — other than our sympathy for Japan, the Japanese people and especially those workers who have stayed on the site of the power plant to work to secure the reactors so they do not become hazards to the population at large.  Those workers may be exposed to significant, harmful radiation, and they deserve all the thanks you can give them.

Below is a map of the contiguous 48 states of the U.S., showing live readings from about a dozen sampling sites across the nation.  The map should update about every minute (if it doesn’t, and  you want to see updates, click through to the Radiation Network site).

Normal background levels are about 25 to 75; a low-level warning might be given if readings are sustained at 100.  These numbers are Counts Per Minute (CPM), a very crude measure from a Geiger counter showing how many radioactive particles or rays hit the sensor in a minute.  It does not distinguish alpha, beta or gamma, and it may be dependent on the design of the Geiger counter, especially the size of the sensor — differently designed machines give different readings even right next to each other.

So it’s a crude count, but it’s a map of counts.

Radiation Network map of radiation in the U.S.  Read legend, use with caution

Radiation Network map of radiation in the U.S. Read legend, use with caution. Click map to go to Radiation Network site.

Here is legend information for the map:

Legend for Radiation Network map

Sampling station symbols, Radiation Network

Nuclear site, calculated by the Radiation Network

At left is a symbol used on the map to mark “nuclear sites” by the Radiation Network.  Note that a nuclear “site” is not necessarily a nuclear power station.  For example, there are nuclear sites designated near Moab, Utah; there are a couple of ore refining facilities or tailing ponds there, but no nuclear power station.  The map shows a nuclear site in the Texas Panhandle.  There is no nuclear power station there.

Instructions on how to read the map, from RadNet:

How to Read the Map:

Referring to the Map Legend at the bottom left corner of the map, locate Monitoring Stations around the country that are contributing radiation data to this map as you read this, and watch the numbers on those monitoring stations update as frequently as every minute (your browser will automatically refresh).  The numbers represent radiation Counts per Minute, abbreviated CPM, and under normal conditions, quantify the level of background radiation, i.e. environmental radiation from outer space as well as from the earth’s crust and air.  Depending on your location within the US, your elevation or altitude, and your model of Geiger counter, this background radiation level might average anywhere from 5 to 60 CPM, and while background radiation levels are random, it would be unusual for those levels to exceed 100 CPM.  Thus, the “Alert Level” for the National Radiation Map is 100 CPM, so if you see any Monitoring Stations with CPM value above 100, further indicated by an Alert symbol over those stations, it probably means that some radioactive source above and beyond background radiation is responsible.

Notice the Time and Date Stamp at the bottom center of the Map.  That is Arizona Time, from where we service the Network, and your indication of how recently the Radiation Levels have been updated to the Map.

(Please note: Any White circles on the map represent Monitoring Stations that are running Simulations, instead of using a real Geiger counter, so any Alert levels that may occur over those stations are to be ignored since they represent only momentary testing.)

Remember, “alert level” is sustained count above 100. But again, be alert that this is only counts per minute, and may be difficult to translate to an accurate radiation reading.

The Radiation Network is an all volunteer operation, no government funding or other involvement.  In fact, the network is seeking volunteers to get a Geiger counter and hook it up to the internet to provide even more real-time readings.  See “How to Participate in the Nationwide Radiation Network.”

If you’re a denier of global warming/climate change, you should use your usual denial tool, claiming that because radiation at background levels is “normal,” no level of radiation can be harmful.  In fact, if you’d make that claim and volunteer to go staff the crews trying to cool the reactors, the entire world would salute you.

Should you be concerned? MIT’s Technology Review explains that the levels of radiation at the plant site itself are quite low, though higher than normal (article by Courtney Humphries).  The article also explains that radiation levels rapidly drop the farther from the plant one is; while we may be able to detect increases in radiation attributable to the radiation from Fukushima site, it is highly unlikely that radiation will exceed safety standards:

In terms of potential health dangers from radiation from the Fukushima Daiichi Nuclear Power Station, “the people who are in the most immediate danger from acute and severe radiation doses are those people who are on site at the moment and who are desperately trying to keep the reactors under control,” says Jacqueline Williams, a radiation oncologist at the University of Rochester Medical Center.

Moving away from the immediate vicinity of the plant, radiation levels drop very rapidly. James Thrall, radiologist-in-chief at Massachusetts General Hospital, says that radiation levels are inversely proportional to the square of the distance from the source: The level at two miles from the source are one-quarter what they are at one mile, and “at 10 miles away, it’s almost an infinitesimal fraction,” he says. Individual exposure also varies widely depending on whether a person is outside or indoors, or shielded with protective clothing. Japanese authorities have evacuated the population living within a 20-kilometer radius of the plant, and have warned those living within 30 kilometers to stay indoors. Some experts say that people living beyond this range have no cause for concern at this time. “This has nothing to do with the general population,” McBride says.

The trickier question is whether lower doses of radiation—well below the threshold of acute illness—could lead to long-term health consequences for those in that area. Thrall says that epidemiological studies on survivors of nuclear attacks on Japan have found that those receiving 50 millisieverts or more had a slightly elevated cancer risk—about 5 percent higher than expected—and that risk seemed to rise with higher exposures. But scientists still vigorously debate whether that risk can be extrapolated down to even lower exposures.

After the nuclear disaster at Chernobyl, the population experienced a surge in thyroid cancers in children. However, scientists found that the culprit was not radiation in the air but radioactive contamination of the ground, which eventually found its way into cow’s milk. Thrall points out that in Japan, this is highly unlikely because the authorities are carefully monitoring the water and food supplies and keeping the public informed, which did not happen at Chernobyl.

More, resources:

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