Answer to Question #11428 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Measurements and Reporting

The following question was answered by an expert in the appropriate field:


How can I establish background radiation levels in my county? Which U.S. agency is responsible for establishing background radiation levels?


These are excellent questions, and the short answer is that it is not a simple task to establish background radiation levels for a specific location. Because background radiation varies with factors like altitude and geology (see the Health Physics Society fact sheet on environmental radiation), many measurements are required to provide a statistically valid background range. The exact number of measurements depends on the size (area) of the location of interest.

In spite of these difficulties, researchers have established background radiation levels for many locations over many decades of research. As an example, research was done by Oak Ridge National Laboratory in the 1970s on background radiation levels in various U.S. states. The report can be found at and provides details of the type of data collected and how it was collected. The reference list includes many other reports of early research into background radiation levels.

More recently, publications such as the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reports, National Council on Radiation Protection and Measurements (NCRP) reports (for example, NCRP 160), and International Commission on Radiological Protection (ICRP) reports summarize results of such research and provide details on how background radiation levels are determined.

In the United States, the Environmental Protection Agency (EPA) has collected radiation levels at many locations. Where these measurements are not affected by radioactive contamination or other sources of radiation (which is likely to be most locations), the radiation levels may be considered to be due to background radiation. The EPA's RadNet measurements are available online at

Another resource for establishing background radiation levels is the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), a document prepared by several U.S. agencies including the Department of Defense, Department of Energy, EPA, and Nuclear Regulatory Commission. The MARSSIM provides information on planning, conducting, evaluating, and documenting radiological surveys for demonstrating compliance with regulations or standards. An important part of such a process is establishing background (or reference) radiation levels to compare with radiation levels in contaminated areas.

So you can see that while it is not a trivial project to establish background radiation levels, it has been done for specific locations throughout the world over many years. If you cannot find background radiation levels for your location published in the scientific literature, the documents cited above may give you some ideas for how such research can be performed.

Linnea Wahl, CHP

Answer posted on 14 December 2015. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.