Answer to Question #13593 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment and Shielding

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

Q

I live in an apartment on the 11th floor. and my window is directly facing a radiology facility of a hospital two blocks away (roughly 24–27 m away). Would scattered or leaked radiation exposure from the radiology facility pose a risk? If so, how significant would that risk be? Also, would living on a higher floor decrease the scattered/leaked radiation exposure coming from this facility?  

A

There is no need to worry about scattered or leakage radiation from the radiology facility. There are two reasons why the situation you describe isn’t a problem. First, radiation exposure drops off with distance based on something called the "Inverse Square Law." Essentially, that means that every time the distance from the radiation source doubles, the exposure is reduced by a factor of 4. Thus, the distance of 24 m or more distance provides a tremendous reduction of the radiation exposure from that facility. While one could theoretically calculate an exposure at that distance, it would be extremely small and impossible to measure.

Second, radiation exposure is also reduced by solid materials between the radiation source, radiation scattered from patients, and the area of interest—your apartment. Scattered radiation from x rays has lower energy which determines the penetrating ability of the radiation. As such, standard building materials and even glass will reduce the radiation exposure by absorbing much of the radiation as it passes through those materials. Thus, the windows and walls of the radiology facility, plus the windows and walls of your apartment would serve as "protective barriers" in addition to the distance. You have no need to worry about radiation exposure from the radiology facility.

Mack L. Richard, MS, CHP

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 28 August 2020. 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.