The U.S. Environmental Protection Agency maintains a network of radiation air monitoring stations stationed throughout the U.S.

Amid fears that harmful radiation from the damaged Japanese nuclear plant could reach U.S. shores, the EPA deployed additional monitors to Guam, Hawaii and Alaska. The monitors are part of RadNet, a national network of monitoring stations that regularly collects and analyzes air samples for radioactivity.

The public has access to the data in near real-time. (There’s generally a 1 to 2 hour delay.)

But the information is a bit dense. We’ve put together a basic guide for how to access the information.

Logging On

Take the following steps — there are many — to log on to the EPA’s Central Data Exchange website:

  • Go to www.epa.gov/cdx
  • On the left side of the screen, click, “Log-in to CDX”
  • On the left side of the screen, click, “Registration”
  • Under “Privacy Statement,” click “Click here to continue”
  • Scroll to the bottom of the screen (after reading the relevant material) and click, “I Accept”
  • If you choose, fill out the required information and follow the screen prompts
  • When given the list of access programs, click, “Radiation Network (RadNet)”
  • There is one more required field that pops up — enter “N/A” into it
  • After an option to select more programs (not necessary), you will be taken to the RadNet page
  • Scroll the map to Hawaii and click on the green bubble above Honolulu
  • This will show a series of data points, indicating radiation near-real-time local radiation levels

Reading the Data

Once you click to view Honolulu’s RadNet monitor data, here’s an example of what you’ll see:


The image shows Gamma gross count ranges and the beta gross count rate. Here’s the EPA‘s explanation of what those are:

  • The beta gross count rate measures the radiation from all radionuclides that emit beta particles, which is indicated by the term gross or total. The term count rate tells us how quickly beta particles are being detected, which indicates how much radioactivity the monitor is seeing.
  • The gamma data measures radiation from all radionuclides that emit gamma rays and splits them into ranges of energy. The word gross, or total, indicates that the measurement is from all gamma emitting radionuclides. Not all gamma rays have the same amount of energy. Breaking the data into discrete energy ranges helps scientists to determine which radionuclides may be present.

Both beta particles and gamma rays occur naturally in the environment, according to the EPA. Scientists look at RadNet data over time to identify what’s “normal.” Anytime there is a reading above “normal,” the EPA is alerted and scientists review the data.

To view Honolulu’s daily radiation report, look here.

Currently, reports show that both beta particles and gamma rays are thousands of times below levels requiring concern.

To get an idea of what’s “normal,” the table below shows figures for gamma ray ranges for the month of March.


As is evident from the tables, levels remain relatively stable for gamma ray ranges. The same has been true with beta particles, which have been at zero levels all month.

RadNet monitors in Sacramento, California have picked up minuscule quantities of the radioactive isotope xenon-133. An EPA press release on Friday stated:

“The origin was determined to be consistent with a release from the Fukushima reactors in Northern Japan…Xenon-133 is a radioactive noble gas produced during nuclear fission that poses no concern at the detected level. These types of readings remain consistent with our expectations since the onset of this tragedy, and are to be expected in the coming days.”