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The Third Annual Thomas S. Tenforde Topical Lecture HPS Ask the Experts

The Most Intriguing Questions and Answers

Roessler, Genevieve S.1; Baes, Fred2; Classic, Kelly3

Author Information
doi: 10.1097/HP.0000000000001238
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THE HEALTH Physics Society (HPS) conceived of the idea of an online “Ask the Experts” (ATE) feature in 1999 when the Society created its website (HPS 2019a). The newly appointed Website Editor, Genevieve S. Roessler, and the new Webmaster, Fred Baes, convened a meeting of a small group of advisors, including HPS members who had extensive publications experience. The group first laid out the basic structure of the website—statement of goals, list of officers, information on meetings, dues structure, rules of the Society, and related topics.

Roessler and Baes suggested that this new online tool would provide a unique opportunity for the Society to reach members of the public with information on radiation safety. They outlined their idea of an online ATE feature to the advisory group. ATE features are popular today, but 20 y ago, it was a novel idea. The group was initially apprehensive about ATE’s possible success but thought that at the upcoming turn of the century, they could be creative and recommended a move forward to develop the editorial and functional structure to support the feature.

Robert L. Brent, MD, a longtime member of the HPS and an emeritus member of the National Council on Radiation Protection and Measurements (NCRP), saw the need for this outreach and helped the website group set the tone for establishing an accessible and credible communication venue. He advocated answering questions in a brief and personal manner.


The ATE structure was developed so people could submit their questions through the website. Instructions stated that only questions in the field of radiation safety would be answered.

Within a few days of the inception of this feature, questions began to arrive. The majority of the questions came from members of the public who had concerns about exposures from a number of different radiation sources. An email with each submitted question went to the website editor for distribution to an appropriate subject expert.

For each question, an expert prepared an answer and sent it to the ATE editor, who reviewed it and sent it promptly and personally by email to the questioner. If the answer to a question was deemed to be of general interest, it was posted on the ATE section of the website. The names of the experts who answered questions were posted, but questioner names were not.

During the first year, one editor, the webmaster, and about 40 experts were able to manage the flow of questions. However, as the volume of questions grew and the type of questions required broader and more in-depth expertise, it was more than what one editor could manage. Subject-area assistant editors, named topic editors, were added as the volume and variety of questions increased. Since questions were submitted by health physicists and other technical people in addition to members of the public, topic editors were added who had specific expertise in the more in-depth technical aspects of radiation safety.

This expanded structure prompted the addition of a procedural requirement that the questioner select from a list of topic areas when submitting a question. This sent the question to the appropriate topic editor, who could then answer the question personally or select an expert in that category for an answer. If the expert prepared an answer, it was sent to the topic editor (with a copy to the main editor). After review, it was sent personally to the questioner.

Currently, the main editor, the webmaster, 20 topic editors, a technical editor, an editorial associate, and more than 300 experts participate in the ATE feature.


Now, 20 y after its inception, the HPS considers its ATE feature a success and the most valuable service the Society offers for the public. Nearly 13,000 questions have been submitted to the feature. All have been answered personally by radiation safety experts.

While it is important to answer each question personally, it is recognized that the most far-reaching impact of the feature is the presence of the answered questions and other written material on the website, which allows people to search for answers to their questions without the necessity of posting a question. The posted material includes frequently asked questions, summary papers on topics of interest, links to other pertinent information, and answers to submitted questions of general interest. It is organized in 26 radiation safety categories. To enhance the information search, all postings, including answers to questions, have a short headline. These serve as keywords that facilitate website searches. This material is all posted at the “Ask the Experts” webpage (HPS 2016).

This feature draws over one million visitors per year. This statistic suggests that a substantial number of people are finding the answers to their questions on the website and, therefore, do not need to submit a personal question.

Reference is also made to another HPS publication, Radiation Answers (HPS 2019b), a document on radiation written especially for the public.


ATE editors have learned much through the years about effective interaction with questioners, especially members of the public.

  • Answers should show compassion. Experts have learned, as Theodore Roosevelt said, “Nobody cares how much you know until they know how much you care.”
  • Answers should present the bottom line first.
  • Answers should be factual, but as brief as possible to get the point across.
  • Answers should use plain language at the cognitive level of the questioner. Experts keep in mind the fact that effective communication occurs among equals.
  • Answers can be supported by reference to published documents. This allows the questioner the option of doing more reading if interested. NCRP publications, HPS position statements, and other peer-reviewed documents add to the credibility of the information for both members of the public and colleagues.



The number of questions received has remained at a consistent level in recent years, and questions continue to cover a wide range of radiation safety issues. The Society’s ATE feature is available for everyone as long as the questions are about radiation safety. Questions that should be answered by physicians or lawyers are not answered. Experts do not do homework for students but often give advice as to where a student can go for an answer. If a question is beyond the expertise of the experts, a recommendation is given as to where the questioner might look further.

Although questions cover a wide range of subjects, by far the most frequent are those that deal with medical exposures. Again, these span a wide range of procedures, but the highest number involve computed tomography (CT) procedures. Other questions from the public deal with a wide range of concerns including contaminated products from Japan, granite countertops, radon, smoke detectors, luggage and whole-body scanners, and radiation exposure from airline travel. Another major concern is exposure to nonionizing radiation sources such as cell phones, radar, ultraviolet radiation, lasers, and power lines.


Questioners cover a wide range—from those with little knowledge of radiation safety and a high level of anxiety to those with knowledge of the field and little or no anxiety who have a need for some specific information. Questioners can be grouped into five categories:

  • Members of the general public: This group is usually the least knowledgeable about radiation safety and, probably because of this lack of knowledge, is the most anxious.
  • The news media: These questioners—who include television, newspaper, and magazine writers—are usually responding to a radiological incident or a report of some perceived or real danger involving radiation or radioactivity. They need a quick response (usually within hours) and information in short bites. They appreciate being able to interview people with radiation safety credentials.
  • Entry-level health physicists and other technical persons: The members of this group often do not have the specific academic background that is necessary for a situation that has come up in their work or academic responsibility. They need an explanation of the basics on a specific concept and recommendations for reference materials where they can go for further learning. A special case includes health physics graduate students who seek direction and references for their academic study.
  • Professionals who are not health physicists: This educated group—which includes other scientists, medical doctors, and lawyers—looks for more detail and backup for their situations and often reassurance that their approach is valid.
  • Professional-level health physicists: This group needs high-level information in an area of the field not specific to their training.


Examples from members of the public

It is difficult to select only a few intriguing questions and answers from the large number that have been submitted in the lifetime of this feature. To give an overview of the scope and variety of information that is sought from members of the public, nine abridged examples are presented.

Education doesn’t necessarily mean knowledge.

Q: I’m pregnant. I need to do business travel by plane. Should I cancel my trips, especially in the first trimester? (Submitted by a radiologist with an MD and a PhD at a major institution.)

A: The dose needed to cause harmful effects for an embryo/fetus is at least 100 millisieverts (mSv). Radiation dose during commercial flight is on the order of 0.01–0.02 mSv per hour of flying time. This means you would need to fly on 1,000 trips of 10 hours each during pregnancy to receive the amount that might be harmful.

Response: “Awesome, thanks for your help.”

Discussion: This first example is a common question demonstrating that a good education does not necessarily mean knowledge about a subject that is somewhat out of a person’s background. This question leads one to wonder why physicians, especially radiologists, are not provided with a better education on radiation and radiation safety. The reality is that in most medical schools, the curriculum is so packed that there is no time to cover this and many other important subject areas.

ATE was a good resource for this physician. The expert gave information on the dose level above which there might be concern, gave typical dose levels during commercial flights, and ended by putting those numbers in perspective. The answer was brief and factual. It worked in this case and a nice thank you note was received.

Radon is a popular subject for questions.

Q: While changing my furnace filter, I checked it with a Geiger counter and found it was radioactive. Is it common for furnace filters to collect radon daughter products?

A: Your interesting observation sent me to my own basement to measure my filter. I found the same result. The initial measurement, taken immediately after I removed the filter, was 10 times the background count in my basement. Measurements over a period of two hours showed that the activity decreased the way you would expect radon-222 decay products to behave. I suspect it is a common occurrence to find this activity on furnace filters. The Health Physics Society has a position statement on indoor radon that you might find helpful ( (HPS 2009).

Discussion: Radon questions are frequently submitted to ATE. The questions often follow the airing of a television ad or a newspaper article about testing for radon in the home. This one may have been prompted by media reports, but the question and the answer were also rather unique. The questioner has a higher level of knowledge than most. His curiosity prompted him to take his Geiger counter and measure his furnace filter.

ATE’s radon expert didn’t get all caught up in theoretical explanations. Instead she grabbed her Geiger counter and measured her own furnace filter to be able to answer the question. She also pointed the questioner to the HPS position statement on radon for more information on the subject. This is another example of a questioner who apparently did not need a lot of equations and scientific backup. Often a simple answer and a reference to a place where more information can be found is all that is needed.

All those waves around us.

Q: My nephew is exposed to WiFi day and night. He has a giant TV screen which he sits close to and he uses an iPad, a cell phone, and a microwave. I have read that this can be harmful. Please send me some research that I can offer him.

A: These kinds of exposures are ordinary in modern society. Eating microwaved food or being near a TV set does not entail any noticeable exposure to electromagnetic fields. While some may involve exposure to radiofrequency (RF) fields, the levels of exposure are far below U.S. and major international exposure limits. The known hazards of RF energy are associated with excessive heating of tissue and do not occur with ordinary use of consumer devices. After half a century of research, no clear evidence has emerged for health risks from low-level exposure to RF fields.

Discussion: Nonionizing sources of radiation like microwaves, radio waves, cell phones, radar, power lines, infrared, and lasers are a source of enough questions to require two ATE topic editors. Usually only one source of exposure is of concern in a question. In this case, a person saw his nephew surrounded by various waves day and night.

The expert’s brief summary of prevalence and effects of RF fields eased the person’s mind about his nephew’s life surrounded by all of his gadgets.

Fukushima is still a worry

Q: I am interested in a classic car located near the Fukushima exclusion zone. What would be involved in decontaminating the vehicle before shipping? Or is it a lost cause?

A: I'm aware that Fukushima fallout was detected on used cars from Japan in 2012, only 1 y after the accident. Now, 7 y later, most of the fallout is gone due to natural decay and weathering. Nothing remains radioactive forever. If the car was garaged, it should be clean. If not, the metal surfaces can be cleaned of any remaining radioactivity simply by washing. The tires could be washed vigorously.

Discussion: The accident at the Fukushima Daiichi Nuclear Power Plant in Okuma, Fukushima Prefecture, occurred following the Tohuku earthquakes and tsunami on 11 March 2011. Eight years later, questions are submitted to ATE by people with a variety of concerns, especially about products produced in Japan.

ATE’s expert provided brief but reassuring information. It appeared that this person really wanted that car, and all he needed was for someone to put his mind at ease.

Better communication skills needed.

Q: I am concerned about radiation exposure from repeated CTs. I asked the radiologist to tell me how much I received during my abdominal scan. The amount was expressed in a way that I cannot convert, 278.29 mGy cm−1 (DLP) [dose-length product].

A: The effective dose from an abdominal/pelvic CT scan is around 4.2 millisieverts (mSv). At effective doses less than 100 mSv, the risk of health effects is too small to be seen. For more information on the risk, check out the HPS position statement, “Radiation Risk in Perspective,” (HPS 2010).

Response: “You're a Prince! I can't thank you enough for your timely and thorough response. This is exactly what I am looking for. I truly wish physicians would be trained to provide this level of objective information rather than the often-palliative responses they use to assuage concerns.”

Discussion: By far the most frequent and most detailed questions are about medical exposures and are asked by the most anxious questioners. These primarily involve CT scans. This example is typical. Because patients are so concerned about radiation exposures, they often ask medical personnel how much dose they have received from an exam.

Had the radiologist in this case been a better communicator, the person’s concern might have been allayed. ATE’s expert gave an estimate of the effective dose and put it in perspective by referring to the appropriate HPS position statement.

Four topic editors are required to handle the questions in the medical subject areas: Medical and Dental Patient Issues (two editors), Medical and Dental Equipment/Shielding, and Nuclear Medicine Issues. A number of medical questions also come in to the Radiation Effects category.

Scary information on the internet.

Q: I have had two barium swallows and two mammograms. I was informed I had a 1:33,000 risk of cancer from the barium swallows and 1:49,000 risk of cancer from my mammograms. I am presuming these calculations are from the LNT (linear no-threshold) model and that the risk is theoretical. Why is the LNT model still used if the risk of cancer associated with medical imaging at doses below 100 mSv is “too small to see?”

A: The expert discussed the conservative approach of LNT, put doses below 100 mSv into perspective, and recommended the Image Gently® website for information on the risks and benefits of medical exposures.

Response: I cannot thank you enough for your reassuring words and for giving me a better understanding of the effects of radiation. Unfortunately, before finding the Ask the Experts page, I read a lot of scary information about radiation, which caused me extreme anxiety.

Discussion: Poor or misleading information on the internet, television, and other media sources can be scary. Presenting the facts in plain language and putting doses in perspective can reassure concerned people. The Image Gently® website (SPR 2014) was recommended for more information.

The answer to this question stimulated this concerned questioner to submit two more detailed follow-up questions. The topic editor expended many pages and much more background information on radiation dose units and quantities and why different dose units are used. This is not an unusual case. It happens fairly often that a questioner will come back for more detailed information and more reassurance. Thus, characteristics of a successful ATE topic editor or expert include patience and understanding.

Concern about cat after a nuclear stress test.

Q: My husband is going to have a nuclear stress test next week. He is to avoid coming within 3.05 m of small children for 24–48 hours post-test. I am concerned about our cat. I am assuming if a young child can potentially be affected, a small animal could as well.

A: You don’t need to be concerned about your cat. The recommendation for your husband to avoid coming within 3.05 m of small children for 24–48 hours after the test is a very conservative precaution. The precaution is not based on size. It is based on the fact that developing cells present in children are more sensitive to radiation than fully developed cells.

Discussion: People are often concerned after a family member has a nuclear medicine procedure. They have been told that the patient will be radioactive for some period of time after the exam. To many people, a pet is part of the family and needs to be seen as such by the expert who answers the question.

Journalist fights radiophobia.

Q: I am a journalist from the Netherlands setting up a website on radiophobia. I cover all kinds of radiation related subjects: hormesis/LNT, Brazilian beaches, radiotherapy, etc. I am interested in the case of Harold McCluskey, who in 1976 was heavily contaminated with americium-241. He lived another 11 y and died of a disease unrelated to the accident. Did someone calculate his lifetime exposure?

A: In a September 1995 Health Physics article on the accident, cumulative absorbed doses to his bone surface, liver, and lung were listed. The article concluded that “the probability of not observing a fatal cancer based on BEIR-IV risk factors for these absorbed doses was 12%.”

Note: The entire article was provided to the questioner along with a suggestion that he join the Society so that he would receive the Journal for reference on other topics of interest for his website.

Discussion: This question was one of the easiest to answer because it only involved the provision of a published article (Toohey and Kathren 1995) containing the information. No interpretation was necessary. The journalist was pointed not only to the article conclusion but to the article’s closing paragraph, which says: “The lack of carcinogenesis in this case does not indicate that currently accepted risk factors for alpha irradiation are in error. Even assuming upper limits of risk, there was a significant (>10%) chance of not observing a cancer induced in this case in the period between exposure and death. In actuality, risks may well have been lower due both to cell killing and the relatively short latent period.”

It is not known at this time what use the journalist has made of this information.

Grand Canyon.

Q: What were the likely exposures and health effects to Grand Canyon museum visitors from the three buckets of uranium ore that were on display there for three decades?

A: We assume your question is prompted by the USA Today article on 19 February 2019 that stated: “For nearly two decades at the Grand Canyon in Arizona, tourists, employees, and children on tours passed by three paint buckets stored in the national park’s museum collection building, unaware that they were being exposed to radiation.” The concern came after a Grand Canyon safety manager released information to the press about “measurements made by Park Service officials, which appeared to be hundreds of times higher than thresholds set by the government for exposure to radiation.”

Discussion: ATE experts reviewed available information and concluded that “the uranium ore in the buckets is a low-risk material that, unless ingested, would not be emitting enough radiation to cause a harmful effect.”

More detailed information is given in an information sheet (HPS 2019c):

ATE editors had been alerted to the USA Today article and were prepared for questions that might come to ATE. The ATE main editor worked with the HPS media liaison to facilitate a response to questions that came in from reporters in Tennessee, Arizona, and several other locations. Responses were handled by phone interviews. Reporters also were referred to an information sheet written by HPS uranium experts and posted on the HPS website that same day (HPS 2019c).

In the days following, several articles appeared in news reports that quoted health physicists. The headline for one of the stories (Wagner 2019) said, “Experts dispute Grand Canyon safety manager’s claim that radiation posed risk to public.” In the weeks that followed, other articles were published suggesting that the radiation levels were overstated as we had originally suspected.

Nonpublic sector

Questions from the nonpublic sector (health physicists, physicians, lawyers, and other technical people and scientists) comprise about 15% of the total received. The questions are almost always much more complex, and the answers require more time and a broader and deeper base of knowledge on the part of the expert.

Because of the complexity involved, individual sample questions and answers are not presented here. Instead, Table 1 lists the question number and titles of the examples to give some idea of the type and level of the questions asked and answered.

Table 1
Table 1:
Nonpublic sector questions.

These questions and answers are posted on the ATE feature of the HPS website and can be accessed by the listed links.


This paper addresses the history and structure of the Society’s ATE feature and gives a sample of the types of questions and answers that have been received and answered over the 20 y of its operation. Lessons learned are also presented. The most rewarding evaluation of the success of the venture came from the Society board, which stated that it considers its ATE feature a success and the most valuable service the Society offers for the public.

ATE editors view the support for the scientists as another significant service offered by ATE.

Editors state that the most important conclusion about this endeavor can be stated briefly, “We help people! Especially the very many, very anxious members of the public.”

That’s why the two dozen editors and the more than 300 experts are such willing volunteers.

No title available.


Current ATE topic areas are listed below along with the names of the prestigious, talented, willing, and hard-working topic editors and staff. It is impossible to estimate how many volunteer people hours go into this effort each year. It is huge and it is very important work.


Health Physics Society. Update on perspectives and recommendations on indoor radon. Position Statement of the Health Physics Society. Herndon, VA: HPS; 2009. Available at Accessed 20 July 2019.
Health Physics Society. Radiation risk in perspective. Position Statement of the Health Physics Society. Herndon, VA: HPS; 2010. Available at Accessed 10 October 2019.
Health Physics Society. Ask the experts [online]. 2016. Available at Accessed 20 July 2019.
Health Physics Society. HPS Specialists in Radiation Protection [online]. 2019a. Available at Accessed 20 July 2019.
Health Physics Society. Radiation answers [online]. 2019b. Available at Accessed 20 July 2019.
Health Physics Society. Uranium at the Grand Canyon—HPS Expert Input. Herndon, VA: HPS; 2019c. Available at Accessed 20 July 2019.
Society for Pediatric Radiology. The Image Gently Alliance [online]. 2014. Available at Accessed 20 July 2019.
Toohey RE, Kathren RL. Overview and dosimetry of the Hanford americium accident case. Health Phys 69:310–317; 1995.
Wagner D. Experts dispute Grand Canyon safety manager’s claim that radiation posed risk to public [online]. 2019. Available at Accessed 20 July 2019.

education; Health Physics Society; National Council on Radiation Protection and Measurements; public information

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