Answer to Question #7498 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Radon

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


I recently conducted air sampling in my basement with a passive alpha track film cannister. I only ran the test for 79 days. The Environmental Protection Agency (EPA) recommends 90 days. The lab will not analyze it. Can I get a count from the lab and do the math myself? I realize it affects the lab's quality control since it is under 90 days. What formula can I use if they give me a count? I had used a short-term test and found between 37 and 74 becquerels per cubic meter (Bq m-3). I have a three-year-old and limited funds and need to sleep at night knowing she is safe. I cannot turn back the clock and get that time back. It was peak exposure during the winter. Now the windows are open. If not, can I get the sample back and send it to another lab that can give me results? What would the ballpark cost of analysis be?


A lab should be able to give you a qualified estimate of your radon concentration based on the 79 days of exposure, versus the normal value of 90 days or more. It should only require an adjustment for the exposure time. Because the time is less than normal, the lab would be understandably reluctant to provide an unqualified result, for which all procedural and quality measures would have had to fall within specifications. There would be fewer alpha tracks than would be produced by the same radon concentration in 90 days, and the measurement uncertainty would be somewhat larger. The lab should qualify the value as an "estimate" rather than a regular result, however. 

Providing estimates of the results from sample analyses is a normal practice in radiological analysis labs when procedures are not followed exactly or other quality assurance aspects of a measurement are out of specification by small amounts. This is especially appropriate in a case such as yours when the exact measurement cannot be reperformed and a new measurement cannot be performed in a reasonable length of time. I suggest trying to contact the laboratory again to request an estimate of the concentration from the available data. Do not hesitate to ask to speak to a supervisor or technical person if you get another unqualified "no."

I do not recommend trying to have the sample analyzed by another laboratory since that lab would probably not have access to the needed calibration data and the specific analytical procedure, which could be considered proprietary by the original lab.

On a related matter, since your short-term screening test was in the range of 37 to 74 Bq m-3, which is less than the EPA recommended action level 4 pCi L-1 (150 Bq m-3)*, it seems unlikely that you or your family would be "unsafe" over the period of time required to remeasure your home.

Tom Gesell, CHP, PhD

*The radon concentration units are given here in pCi L-1 (called traditional units) because those are the units used by the Environmental Protection Agency. However, the Health Physics Society has adopted SI (International System) units and these are given in parentheses.

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 12 May 2008. 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.