Answer to Question #14692 Submitted to "Ask the Experts"

Category: Regulations, Policies, and Standards — Regulations and Guidelines

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

Q

The ICRP dose limit for occupational exposure is relatively high, at 20 milisievert per year (mSV y-1) compared to 1 mSV y-1 for members of the general public. Why? The same human physiology governs both workers and members of the public. At the same radiation exposure, aren't both of them at the same risk? If yes, then why this large difference in dose limit?

A

Risk is a tricky thing to quantify especially in radiation exposures. While family history, diet, smoking, and other factors may impact an individual's risk of cancer, much debate still exists whether low levels of radiation exposure (20 mSv or 1 mSv) increase, decrease, or do nothing to change that risk of cancer. Statistically, scientists conducting studies with large populations do not consistently find increases in cancer for these low-level radiation exposures. The Health Physics Society (HPS) Position Statement on Radiation Risk in Perspective advises against estimating health risks to people from exposures to ionizing radiation that are near or less than natural background levels because statistical uncertainties at these low levels are great.

While you are correct in stating 1 mSV y-1 is the limit for a member of the public, realize this is the limit that each facility or licensee may not exceed. It would be possible that a person with several exposure events within this 1 mSv limit from several different facilities would accumulate a dose exceeding 1 mSv and possibly approach 20 mSv. A nuclear worker who chooses the profession is allowed a higher limit (although at this low dose it does not directly correspond to a higher risk), typically from a single facility or licensee, as part of their occupation. Miners and farmers are at higher risk for on-the-job injury than nuclear workers, for example.

To answer your question, much debate still exists if there's any risk at all with a 20 mSv or 1 mSv exposure to ionizing radiation. Our bodies have evolved powerful immune systems which regularly repair damage from viruses, breathing oxygen, and exposure to ionizing radiation. These values were chosen to be well below the level at which human harm is known to occur, and if spread out through an entire population of nuclear workers and the public, any increase in risk, if it exists, is too low to be measured. While 20 mSv may be 20 times higher than 1 mSv, and alone that comparison may be alarming, consider taking one airplane flight this year and 20 airplane flights next year. Statistically, your chance of harm from even 20 airplane flights is infinitesimal when compared with the risk of harm by simply driving your vehicle to the airport terminal.

I hope this helps.

Daniel Sowers, CHP

Answer posted on 3 October 2022. 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.