Answer to Question #9778 Submitted to "Ask the Experts"

Category: Environmental and Background Radiation — Building and Construction Material

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

I recently read that construction materials, such as brick and stone, give off more radiation than something such as wood, and I saw a YouTube video where someone put a Geiger counter next to brick and it read either 3 or 0.3 microsieverts per hour. It was three times the level of the air. Is this much of a hazard, and how far away from a brick wall would one have to be to be at background levels? I am considering buying a home with a brick front and some of the kids' rooms would be sharing the same walls. Estimates of doses I've seen range from 7 mrem to 100 mrem per year extra for people living in brick or stone homes. I am basically wondering if we should buy the house and, if we do, try to distance the beds as far from the brick walls as possible. Is this necessary?

It is true that brick and stone are likely to be more radioactive than wood, simply because brick and stone contain more naturally radioactive material like uranium and thorium. Scientific studies (which YouTube videos most definitely are not!) have found that for brick-veneer houses, the building materials contribute about 0.008 microsievert (µSv) per hour. This value is from the National Council on Radiation Protection Report 160, Ionizing Radiation Exposure of the Population of the United States.

The same report provides an estimate of our overall dose from "ubiquitous" background radiation, which includes the dose from building materials in our homes. In the United States, our overall dose from natural background radiation is about 3.11 millisieverts (mSv) per year or 311 millirem (mrem) per year. Of this, about 0.07 mSv/y (7 mrem/y) is from building materials.

The higher dose rates that you cite may be from dwellings in other parts of the world, which typically use much different building materials and techniques than in the United States. There are reports of research done on indoor dose rates in China, Nigeria, Norway, Ireland, and the Netherlands ranging from 0.1-1.3 mSv/y (10-130 mrem/y).

There is little or no risk to you and your family from the brick in the house. The Health Physics Society has published a position paper on this topic (see PS005-3, "Ionizing Radiation Safety Standards for the General Public").The Society's position is that dose rates up to 1 mSv/y (100 mrem/y) above the annual natural radiation background are acceptable because at this dose, risks of radiation-induced health effects are either nonexistent or too small to be observed.

Linnea Wahl, Certified Health Physicist

Answer posted on 15 July 2011. 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.