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Japanese Nuclear Emergency: Radiation Monitoring

Frequently Asked Questions

EPA no longer updates the information at this link, but it may be useful as a reference or resource. This site contains information and data from March 11, 2011 to June 30, 2011. EPA has returned to routine RadNet operations. This site will continue to be available for historical and informative purposes.

For real-time air monitoring data, please visit the EPA RadNet website and Central Data Exchange. To view both current and historical laboratory data, please visit our Envirofacts database.

Has EPA detected elevated radiation levels in the U.S.?

After a thorough review of all U.S. sampling and monitoring, the results from the accelerated sampling done in March and April 2011 showed that the radiation levels remained well below any level of public health concern and were consistently declining. This page discusses RadNet data from March 11, 2011 to June 30, 2011 only. To view historical data from that time period, please visit our EPA RadNet Monitoring Data webpage. For results for other dates, please visit our Envirofacts webpage. For real-time air monitoring data, please visit the EPA RadNet webpage.

On this page:

General RadNet Information

Precipitation, Drinking Water and Milk Sampling

Precipitation

Drinking Water

Milk

General RadNet Information

What is the difference between the data gathered by the stationary and deployable monitors?

  • The data gathered by the stationary monitors and the deployable monitors are different.
    • The stationary monitors send beta gross count rate and gamma gross count rate ranges.
      • 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 raysand 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.
    • The deployable monitors show external exposure rate.
      • The graph shows the external exposure rate data, which is the dose, or amount of radiation, you would receive on the outside of your body if you were standing in that particular location. Background, or normal, radiation levels depend on factors including altitude and the amount of naturally occurring radioactive elements in the soil. Background external exposure rates typically range between 0.005 and 0.020 millirem per hour (mR/hr).
    • Both sets of data provide us with information on the type and amount of radioactive material in the air, and both serve the same purpose: to notify scientists, in near real time, of elevated levels of radiation so they can determine whether protective action is required.
    • Following the Japanese nuclear incident, all of our near real time data showed background radiation levels.

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What are EPA's radiation air monitoring capabilities?

  • EPA's nationwide radiation monitoring system, RadNet, continuously monitors the nation's air and regularly monitors drinking water, milk and precipitation for environmental radiation.
  • The network contains more than 100 air monitors across the United States and 40 deployable air monitors that can be sent to take readings anywhere in the country.
  • The near-real-time air monitoring data is continually reviewed by computer, and if the results show a significant increase in radiation levels, EPA laboratory staff is alerted immediately and further reviews the data to ensure accuracy.
  • The system has been used to track radioactive material associated with foreign atmospheric nuclear weapons testing as well as for monitoring foreign nuclear accidents such as Chernobyl.
  • EPA maintains additional monitoring capabilities that can be deployed to any location in the United States or its territories.

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Is this monitoring able to cover the whole U.S.?

  • During the last five years, EPA has been upgrading the nationwide RadNet system by installing new near-real-time radiation air monitors across the country. Currently the RadNet system contains more than 100 real-time radiation air monitors in 48 states. EPA also has 40 deployable monitors that can be sent to supplement the system.

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What are deployable monitors? What do they measure?

  • EPA has 40 deployable radiation air monitors that can be sent anywhere in the United States to gather data.
  • The RadNet deployable monitors have built in weather stations and measure gamma radiation.
  • Like all RadNet radiation air monitors, the RadNet deployable monitors send both weather and gamma radiation readings hourly to EPA's National Air and Radiation Environmental Laboratory.

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When is air monitoring data available to the public?

  • The near-real-time air monitoring data are continually reviewed by computer and are usually posted to EPA's Central Data Exchange website within 2 hours of arriving at the laboratory.
  • If the results show an abnormality in radiation levels, EPA laboratory staff is alerted immediately and reviews the data to ensure accuracy before posting.

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How does EPA share this data?

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I read about the RadNet system, are these additional units linked into that system or are they different units?

  • The deployable monitors are part of the larger RadNet system.
  • When RadNet deployable monitors are in the field they operate like the stationary radiation air monitors. The RadNet deployable monitors send radiation air monitoring data to EPA's National Air and Radiation Environmental Laboratory hourly.

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Why do I have to log-in to the CDX site to get this information?

  • You do not need to log-in to CDX. In an effort to make EPA's RadNet data more easily accessible and understandable, we have created a webpage with graphs of the monitoring data from across the country between March 11, 2011 and June 30, 2011. You can access that information at http://epa.gov/japan2011/rert/radnet-data-map.html. For current real-time air monitoring data, please visit the EPA RadNet website and Central Data Exchange. To view both current and historical laboratory data, please visit our Envirofacts database.

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Where has EPA deployed additional radiation air monitors?

  • EPA maintains additional deployable radiation air monitors that can be sent to any location in the United States or its territories.
  • EPA made the decision to deploy additional monitors to aide us in gathering data from a position closer to Japan.
    • EPA sent two radiation air monitors to Guam.
      • In an effort to cover the widest possible area, one of those monitors from Guam was transferred to the Northern Mariana Islands in Saipan.
    • EPA sent two additional monitors to Hawaii.
    • EPA sent three additional air radiation monitors to Alaska.
      • The additional monitors were set up in Dutch Harbor, Juneau and Nome. The EPA deployable monitor in Juneau is in need of repair and has been returned to a staging area.
      • Since the Juneau stationary monitor continues to collect and report data, the deployable monitor will not be re-deployed.

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How does the EPA monitor radiation if the monitor in my area is temporarily unavailable?

  • EPA's RadNet monitors are highly sophisticated technical devices which occasionally require maintenance and repair. That is why we placed over a hundred monitors across the country - so we would have an abundance of monitors to provide overlapping coverage. If a monitor in one area is being repaired, EPA's network will still be able to detect any fluctuation in background levels. Following the Japanese nuclear incident, the RadNet air monitors across the U.S. showed typical fluctuations in background radiation levels. The levels detected were far below levels of concern. As the Nuclear Regulatory Commission has said, we did not expect to see radiation at harmful levels reaching the U.S. from damaged Japanese nuclear power plants.

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Why does the beta graph for my location not show current data?

  • The RadNet beta detector is designed to measure beta emissions from particulates on the filter. In some cases, external factors affect the beta detector system, resulting in readings that do not accurately represent the actual beta levels. This interference can come from issues such as radio wave interference. Since the readings do not represent the physical value for beta-emitting particulates in the air, the data are disapproved and not reported on the graph.

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Precipitation, Drinking Water and Milk Sampling

Precipitation

Are the levels we're seeing in precipitation likely to lead to harmful levels in milk and/or drinking water?

  • While short-term events such as these do not raise public health concerns, the U.S. EPA took steps to increase the frequency of monitoring of precipitation, drinking water, and other potential exposure routes.

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Did the levels found in rainwater exceed EPA drinking water MCLs? If so, why shouldn't people be concerned?

  • While the levels in the rainwater exceeded the applicable Maximum Contaminant Level (MCL) of 3piC/L for drinking water, it is important to note that the corresponding MCL for iodine-131 was calculated based on long-term chronic exposures over the course of a lifetime 70 years. The levels seen in rainwater were expected to be relatively short in duration.

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How often does EPA sample precipitation?

  • EPA scientists routinely test precipitation samples from more than 30 sites in the U.S. The stations submit precipitation samples to the EPA lab as rainfall, snow or sleet occurs. Under routine circumstances, samples are analyzed by EPA scientists monthly.

    EPA performs gamma analysis on each sample, followed by the routine analyses. Routine analysis of precipitation for gamma emissions takes about a week from the time the lab receives the sample. This is to ensure the proper analysis and quality assurance (QA) takes place before the results are released. The tests for specific radioactive material may take longer.

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Why is EPA sampling precipitation?

  • Sampling precipitation for radioactive contaminants is one way to help public health officials ensure that food and water supplies are safe for the public.

    In the event of a serious nuclear power plant accident, radioactive material may be released into the environment. Some of this radioactive material attaches itself to dust particles in the air and can be carried long distances in the wind. When these particles are caught in precipitation, e.g., rain or snow, they are deposited directly onto the ground. After landing on the ground, they may potentially contaminate drinking water sources and growing food supplies.

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Drinking Water

How do I know if my water is impacted by the Japanese nuclear incidentJapanese radiation if there is no RadNet water sampling in my town?

  • EPA's RadNet Drinking Water Program obtains quarterly drinking water samples from more than 50 sites across the country. Following the Japanese nuclear incident, our sampling stations nationwide immediately collected samples and sent them to our laboratory for analysis.
  • EPA conducted a second round of drinking water and milk sampling in April 2011, which came after EPA accelerated its normal quarterly sampling efforts for drinking water and milk. This second round of sampling allowed EPA to maintain an accurate understanding of radiation in the environment associated with the Japanese nuclear incident and share the most up to date data with the public.
  • After a thorough data review showing declining radiation levels related to the Japanese nuclear incident, EPA has returned to the routine RadNet sampling and analysis process for precipitation, drinking water and milk.
  • All of this is in addition to the 24/7 near-real-time air monitoring our network provides.
  • The low levels of radioactive material in air, precipitation, drinking water and milk that EPA has seen since the Japan nuclear incident were expected. To date, all of EPA's sampling and monitoring results have been below levels of public health concern.

How do I know if my water is impacted by the Japanese nuclear incident if there is no RadNet water sampling in my town?

  • The RadNet radiation monitoring system provides a national network for tracking radiation levels across the country. The system utilizes over 50 drinking water monitoring sites in the United States, and, because radioactive material from Japan was widely dispersed, reporting from multiple locations throughout the country showed impacts to the nation as a whole.

    Elevated levels of radioactive material in rainwater were expected as a result of the nuclear incident after the events in Japan since radiation is known to travel in the atmosphere. Short-term elevations such as these do not raise public health concerns and the levels seen in rainwater were expected to be relatively short in duration. 

    It's important to remember that radioactive material from Japan traveled thousands of miles through the air before reaching the U.S. The material was widely dispersed and diluted by wind and weather.

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What federal standards exist that address radiation in drinking water and milk?

  • Under the Safe Drinking Water Act, EPA has set maximum contaminant levels (MCLs) to establish limits of certain substances in drinking water, including microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals, and radionuclides. These MCLs apply only to drinking water. 

    EPAs drinking water MCL for the radionuclide iodine-131 is 3 picocuries per liter. It is important to note that this drinking water MCL was calculated based on long-term chronic exposures over the course of a lifetime 70 years.

    EPA samples milk for radioactive iodine helps ensure that the milk supply is safe for the public by identifying potentially contaminated milk. The Food and Drug Administration has set derived intervention levels (DILs) to assure that no one will reach a specific dose that would warrant protective actions as a result of a release of radionuclides. These levels also help the agency determine whether domestic food in interstate commerce or food offered for import into the United States presents a safety concern. FDA's DIL for iodine-131 in milk is 4,770 picocuries per liter. FDA's DIL for total cesium in milk is 33,000 picocuries per liter.

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Is EPA collecting additional milk or drinking water samples?

  • EPA conducted a second round of drinking water and milk sampling in April 2011, which came after EPA accelerated its normal quarterly sampling efforts for drinking water and milk. This second round of sampling allowed EPA to maintain an accurate understanding of radiation in the environment associated with the Japanese nuclear incident and share the most up to date data with the public.
  • After a thorough data review showing declining radiation levels related to the Japanese nuclear incident, EPA returned to the routine RadNet sampling and analysis process for precipitation, drinking water and milk.
  • The low levels of radioactive material in air, precipitation, drinking water and milk that EPA has seen since the Japan nuclear incident were expected. To date, all of EPA's sampling and monitoring results have been below levels of public health concern.

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What actions would EPA take if there were elevated levels of I-131 in drinking water?

  • EPA's MCL for I-131 in drinking water is 3 pCi/L. This level was set to be protective over a 70 year period of continuous intake at that level. A slight increase over this level for a short period would not necessarily cause a public health concern.

    If a water system is found to have levels higher than the MCL for a sustained period of time, the water system administrators would likely explore options for how to lower the levels. This could include finding alternate sources or additional treatment.

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Milk

Does EPA test milk for radiation contamination?

  • As part of our efforts to ensure that there is no public health concern in the U.S. related to radiation exposure, EPA routinely samples cow milk at more than 30 stations every three months. 
  • EPA conducted a second round of drinking water and milk sampling in April 2011, which came after EPA accelerated its normal quarterly sampling efforts for drinking water and milk.
  • This second round of sampling allowed EPA to maintain an accurate understanding of radiation in the environment associated with the Japanese nuclear incident and share the most up to date data with the public. After a thorough data review showing declining radiation levels related to the Japanese nuclear incident, EPA returned to the routine RadNet sampling and analysis process for precipitation, drinking water and milk.
  • The low levels of radioactive material in air, precipitation, drinking water and milk that EPA has seen since the Japan nuclear incident were expected. To date, all of EPA's sampling and monitoring results have been below levels of public health concern.

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Why is milk sampling important?

  • Sampling milk for radioactive iodine helps ensure that the milk supply is safe for the public by identifying potentially contaminated milk.

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Why has EPA increased their milk sampling?

  • EPA's existing milk sampling routine would have RadNet operators collect milk samples during the first week in April 2011. Because of the accelerated schedule, our sampling stations across the nation collected the samples immediately.

    This action was precautionary, to make sure that we were gathering as much data as possible in order to inform our scientists and the public.

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What is the estimated time for obtaining milk testing results?

  • From the time the sample analysis begins, we can have preliminary results within four hours, but a complete analysis can take up to three days.

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Did Japan test for contaminated milk and, if so, what was found?

  • Yes, Japan tested milk. FDA coordinated with the Japanese government to ensure products from the affected prefectures do not pose a health risk to U.S. consumers. Please see the FDA website for more information http://www.fda.gov/.

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What federal standards exist that address radiation in drinking water and milk?

  • Under the Safe Drinking Water Act, EPA has set maximum contaminant levels (MCLs) to establish limits of certain substances in drinking water, including microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals, and radionuclides. These MCLs apply only to drinking water. 

    EPAs drinking water MCL for the radionuclide iodine-131 is 3 picocuries per liter. It is important to note that this drinking water MCL was calculated based on long-term chronic exposures over the course of a lifetime 70 years.

    EPA samples milk for radioactive iodine to help ensure that the milk supply is safe for the public by identifying potentially contaminated milk. The Food and Drug Administration has set derived intervention levels (DILs) to assure that no one will reach a specific dose that would warrant protective actions as a result of a release of radionuclides. These levels also help the agency determine whether domestic food in interstate commerce or food offered for import into the United States presents a safety concern. FDA's DIL for iodine-131 in milk is 4,770 picocuries per liter. FDA's DIL for total cesium in milk is 33,000 picocuries per liter.

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Is EPA collecting additional milk or drinking water samples?

  • EPA conducted a second round of drinking water and milk sampling in April 2011, which came after EPA accelerated its normal quarterly sampling efforts for drinking water and milk. This second round of sampling allowed EPA to maintain an accurate understanding of radiation in the environment associated with the Japanese nuclear incident and share the most up to date data with the public.
  • After a thorough data review showing declining radiation levels related to the Japanese nuclear incident, EPA returned to the routine RadNet sampling and analysis process for precipitation, drinking water and milk.
  • The low levels of radioactive material in air, precipitation, drinking water and milk that EPA has seen since the Japan nuclear incident were expected. To date, all of EPA's sampling and monitoring results have been below levels of public health concern.

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