Meet the "Ask the Experts" Editors

by Genevieve S. Roessler, Ask the Experts Editor

Do you have a question about radiation safety? Both health physicists and members of the public have questions and are finding help on the Health Physics Society (HPS) website "Ask the Experts" (ATE) feature. Since the inception of the feature a number of years ago, nearly 12,000 questions have been submitted. Many of these questions and answers have been posted under 28 subject categories on the site. Questions, whether posted or not, either are answered personally by an appropriate expert or a formal answer is not given because the question is not in the field of radiation safety. In the latter case, a recommendation is made to the questioner as to where the information might be obtained.

An average of 10 to 12 questions come in per week. How many people does it take to manage this workload? Until several years ago, it took one editor (me), our webmaster, and about 40 experts. It soon became obvious that more help was needed due to the number of questions and also because of the need for more in-depth scientific expertise than one editor could provide.

Now, two associate editors, 20 topic editors, and nearly 300 experts participate in the ATE feature. When a question is submitted, the person is asked to select a subject category. The question then goes to the topic editor responsible for that particular category. The topic editor either answers the question or assigns it to an expert in the field. The expert drafts an answer and sends it to the topic editor. The topic editor reviews it and then sends it as a personal response directly to the questioner. If the topic editor decides that the question and answer is of general interest, he or she will review it for technical and scientific accuracy and then forward it to me. I review it again for scientific accuracy, consistency, editorial appropriateness, and grammar. It is then posted on the ATE part of the HPS site.

We have found that many media personnel use the information we have posted under our ATE section of the HPS website. For more specific information, media personnel can contact Outreach Editor Kelly Classic (

Bios and photos of the ATE editors follow.

Editor, "Ask the Experts"

Gen Roessler is a University of Florida associate professor emeritus and now resides in Minnesota. She has served on scientific advisory committees for the Environmental Protection Agency (EPA), the Centers for Disease Control and Prevention, and the National Cancer Institute. She is a distinguished emeritus member of the National Council on Radiation Protection and Measurements (NCRP) and was appointed in 2001 to the Presidential Advisory Board on Radiation and Worker Health. She holds a BA in mathematics from Jacksonville University and an MS in radiation biophysics and a PhD in radiological engineering from the University of Florida. Her specialties are radiation dosimetry, radiation biology, and communications. At the University of Florida she was head of health physics and medical physics in the Department of Nuclear Engineering. Gen is a past president of the HPS and a former editor in chief of Health Physics, Health Physics News, and the HPS website. She was awarded the HPS Distinguished Public Service Award in 2011.

Associate Editor

John Jacobus began his career in health physics as a commissioned officer in the U.S. Navy after receiving master of science degrees from Pennsylvania State University in 1973 and in 1976. During his naval career, he served on submarine repair ships based in Charleston, South Carolina, and in Guam when deployments were made to Diego Garcia in the Indian Ocean and to the Philippines. Other assignments included the Armed Forces Radiobiology Research Institute in Bethesda, Maryland, and as the radiation safety officer for both the Naval Hospital in Charleston, South Carolina, and the National Naval Medical Center in Bethesda, Maryland. Following retirement as a lieutenant commander in 1994, he worked as the junior medical physicist at a private hospital in Dallas, Texas. John joined the staff of the currently named Division of Radiation Safety at the National Institutes of Health in Bethesda, Maryland, in 1995. After 21 years John retired at the end of April 2016. For over 10 years, he was the topic editor for the Medical and Dental Patient Issues area of the ATE feature on the HPS website. In 2000, John was certified by the ABHP and maintains his certification. He was selected a fellow of the HPS in 2004 and is an emeritus member of the American Association of Physicist in Medicine.


Kamran Vaziri received his PhD in nuclear physics from Utah State University in 1987, doing his doctoral thesis work at Los Alamos National Laboratory. He then worked on nuclear physics experiments at the University of Colorado Nuclear Physics Laboratory and later joined Rensselaer Polytechnic Institute, working on experiments at Brookhaven National Laboratory, Jefferson Lab, and Massachusetts Institute of Technology Bates Linear Accelerator Center. Kamran joined Fermilab's Radiation Physics group in 1992. He has been working on radiation physics problems and reviews of different accelerators and experiments. As a radiation physicist, his responsibilities include radiation physics modeling and calculation in support of experiments and accelerators designs, site radiation measurements and instrumentation, environmental measurements, regulatory issues, Fermilab radiation safety interlocks coordinator, and national emission standards for hazardous air pollutants (NESHAP) coordinator. He is the radiation safety coordinator for the NOvA experiment at Fermilab. Kamran has coauthored more than 100 scientific and technical papers regarding radiation physics and nuclear physics. He is an occasional book and article reviewer for Health Physics. He has taught a radiation physics course at the U.S. Particle Accelerator School and has taught radiation monitoring and environmental monitoring courses at the HPS professional development school. He is the past president of the HPS Accelerator Section.

Alpha Emitters

Ronald L. Kathren is professor emeritus at Washington State University at Tri-Cities and president of The Kathren Group, Inc., an environmental health physics and safety consulting firm. He holds degrees from the University of California, Los Angeles and the University of Pittsburgh and is certified by both the American Board of Health Physics (ABHP) and the American Academy of Environmental Engineers. In a career that spans nearly 50 years, he has received numerous honors and awards, including the Elda E. Anderson Award and the Distinguished Scientific Achievement Award of the HPS. His more than 175 papers in the peer-reviewed scientific literature as well as several textbooks, including Radioactivity in the Environment and Radiation Protection, attest to his broad background in the radiological sciences. His primary interests are environmental radioactivity; history of the radiological sciences; biokinetics and health effects of uranium, plutonium, and the transuranium elements; and radiation dosimetry.

Cell Phones, Lasers, Microwaves, Ultraviolet, and Radar

Gary H. Zeman is an expert on radiation health matters and is certified as a health physicist by the ABHP. He received an ScD degree from Johns Hopkins University. He served a 20-year career as a radiation health officer in the U.S. Navy Medical Service Corps, retiring from the U.S. Navy with the rank of commander. Following his naval service, Gary held the positions of radiological safety officer at Argonne National Laboratory in Illinois, radiological control manager at Lawrence Berkeley National Laboratory (LBNL) in California, and manager of radiation protection and product safety at AT&T Bell Laboratories/Lucent Technologies in New Jersey. At Bell Labs/Lucent Technologies, Gary led the department that dealt with evaluating product safety for wireless and optical communications systems, including cell phones and lasers. He teaches graduate-level courses in radiation dosimetry and operational health physics at the Illinois Institute of Technology master's program in health physics. He has authored a number of publications on ionizing and nonionizing radiation effects and measurements. He serves as a member of the National Council on Radiation Protection and Measurements and was a member of the former Veterans Advisory Board on Dose Reconstruction.

Computers and Consumer Products

Orhan SuleimanOrhan Suleiman is involved in a variety of Food and Drug Administration (FDA) initiatives involving human research with radiolabeled drugs, imaging in drug development, and drug safety issues. His current tenure in FDA's drug center complements his earlier experience in the Center for Devices and Radiological Health, where he was responsible for the Nationwide Evaluation of X-Ray Trends (NEXT) survey program and was actively involved in the Mammography Quality Standards Act of 1992. He served as the executive secretary of FDA's Technical Electronic Products Radiation Safety Standards Committee and was responsible for consumer products such as sunlamps, cellular telephones, personnel security systems, and medical products such as fluoroscopy and computed tomography (CT). He served as the NCRP subcommittee chair (Consumer Products) for the 2009 report on radiation exposure to the U.S. population and also represents the FDA on the Nuclear Regulatory Commission's (NRC) advisory committee on the medical use of isotopes. Orhan received his BS (1970) and MS (1972) from the University of Florida and his PhD (1989) from the Johns Hopkins School of Hygiene and Public Health. He is a fellow of the American Association of Physicists in Medicine (AAPM). He has served on a variety of national and international organizations and numerous committees and has published and lectured extensively. 

Decommissioning and Radioactive Waste Disposal

Tim Vitkus is the survey and technical operations director at Oak Ridge Associated Universities (ORAU), managing the health physics, laboratory, and professional training groups who provide technical support to the Department of Energy, the Nuclear Regulatory Commission, and other customers at decommissioning project sites throughout the country. He received a bachelor's in biology from Emory University and a master's in applied and environmental microbiology from Georgia State University. He began working with ORAU in 1990, taking responsibility for planning and implementing radiological and environmental investigations, characterizations, and independent evaluations. He received American Board of Health Physics certification in 2000 and has over 30 years of radiological site assessment and decommissioning experience involving over 50 decommissioning projects. Tim also conducts radiological survey and site investigation training both domestically and internationally. Prior to working with ORAU, he specialized in Resource Conservation and Recovery Act and Toxic Substances Control Act remediation, transportation, treatment, and disposal projects. He has served as secretary for the local Health Physics Society (HPS) chapter, and as president of the HPS Decommissioning Section. He served on the American National Standards Institute N13.49 working group and has authored or contributed to numerous professional papers and presentations, technical reports, and regulatory guidance documents.

Environmental and Background Radiation

LinneaLinnea Wahl is a native of Minnesota and an alumnus of the University of Minnesota (bachelor's in liberal arts, 1976; master's in technical communication, 1986). While working as a technical editor at Los Alamos National Laboratory in New Mexico, Linnea became interested in health physics and completed a master of science in the field in 1993. She obtained certification in 1996, working in Los Alamos as an environmental health physicist. In 1999 Linnea took a position at LBNL in Berkeley, California. Linnea was program leader for environmental radiation protection at LBNL until 2013, when she retired from LBNL. Currently, Linnea works with the HPS Web Operations team, providing technical writing and editing support for ATE, Health Physics News, and special publications. Linnea is a fellow of the HPS, past member of the HPS Board of Directors, past president of the HPS Accelerator Section, and past secretary of the Northern California Chapter of the HPS.

Health Physics Society and AAHP

Howard Dickson received an undergraduate degree in education and a master's degree in physics. He began his career teaching health physics at ORAU and went on to a diverse 40-year health and safety career with leadership positions at Oak Ridge National Laboratory (ORNL), at the Nevada Test Site, and with Bechtel National at Three Mile Island, EG&G, in support of homeland security, and at Johnson Controls at Livermore National Laboratory. He is an HPS fellow, past president, past treasurer, and past director and a recipient of the HPS Elda E. Anderson Award. He has also served as treasurer and past president of the American Academy of Health Physics (AAHP) and has received the Joyce Davis Award from AAHP. In addition to being a certified health physicist, Howard is a certified industrial hygienist and a certified safety professional. Howard currently serves the HPS as the Web Operations editor in chief.


Ray Johnson directed the Radiation Safety Academy from 1985 to 2007 until merging with Dade Moeller & Associates, where he now serves as vice president for training. From 1970 to 1985, he served as a commissioned officer in the U.S. Public Health Service on a permanent assignment to the U.S. EPA, where he served as chief of the Radiation Surveillance Branch. From 1988 to 2006, he managed a contract for radiation safety services at the National Institutes of Health. He has been a member of the HPS since 1966 and served on the Executive Committee for nine years as secretary, treasurer, and president. He has also served local chapters for over 40 years—in particular the Baltimore-Washington Chapter, where he edited its newsletter for 25 years, served as president in 1990, and is now an honorary life member. He has chaired and served on many HPS committees, including as chair of the History Committee since 2004. He is currently treasurer of the AAHP. He is a fellow of the HPS and certified by the ABHP since 1983. He has graduate degrees from Massachusetts Institute of Technology and Harvard and spent six years on doctoral studies at Rensselaer Polytechnic Institute. He has over 30 professional-society awards and has authored over 500 book chapters, articles, professional papers, training manuals, technical reports, and presentations on radiation safety and radiation risk communication. 

Homeland Security/Security Screening

Tom O'Connell has an extensive background in radiation safety and chemical, biological, radiological, nuclear, and high-yield explosives (CBRNE) response. He is a fellow of the Health Physics Society and is an expert instructor for the International Atomic Energy Agency. He maintains Pro Board accreditation as a National Fire Protection Association Fire Service Instructor II through the Massachusetts Fire Training Council and holds an MS degree in radiological sciences and protection from the University of Massachusetts Lowell.  

He recently retired from the Massachusetts Department of Public Health after 37-plus years in public service. The last 12 years he served as the department liaison to the Massachusetts Department of Fire Services Hazardous Materials Response Division.

During his service to the Commonwealth, he was an on-scene responder to various hazardous materials incidents. In his liaison role, he coordinated connecting public safety and public health response with the health care infrastructure.

Tom teaches radiation safety and emergency response to all types of responders around the world. For more than 30 years he has worked with and provided practical aspects of response and interdiction training to fire departments, emergency medical services, law enforcement organizations, the Federal Bureau of Investigation, emergency management officials, hazardous materials teams, and regulatory and foreign government representatives.

Industrial Radiation and Radiation Effects

John Hageman is a certified health physicist, radiation safety officer, and principal scientist at Southwest Research Institute® (SwRI®). He has a BS in physics from the University of Texas (UT) at Arlington and an MS in radiological sciences-medical health physics from the UT Health Science Center at San Antonio. At SwRI he is responsible for the use of a large variety of radionuclides under a broad radioactive material license issued for research and development. He is also responsible for the safe operation of a large variety of radiation-producing machines used for laboratory analysis and the High-Level Radiation Effects Facility, which is licensed for sealed sources of 60Co and 137Cs. He holds a patent on a charged-particle powered battery and has consulted in the design analyses for hot cells and accelerator shielding. He was a manager with the Center for Nuclear Waste Regulatory Analyses at SwRI for several projects for the NRC's high-level radioactive waste program. He also worked with Westinghouse Electric Corporation as a nuclear plant engineer, where he supervised plant operations and the training of Naval officers at the Idaho Naval Reactors Facilities. For the HPS, he is an associate editor of Operational Radiation Safety (1999–present), was a member of the Board of Directors (2003–2005), became a fellow in 2004, and served as treasurer-elect/treasurer (2009–2012).

Instrumentation and Radiation Basics

George Chabot is currently professor emeritus at the University of Massachusetts Lowell, where he previously served as professor of radiological sciences in the Physics Department and, for many years, as radiation safety officer for the university. He serves as a consultant in radiation science and radiation protection to public utilities, industry, medical facilities, government agencies, and others. His earlier work experience includes employment as an analytical organic chemist in private industry and six years of work as a radiochemist and in the training group of the Radiological Health Branch of the U.S. Public Health Service (now the FDA). He has been active in the HPS, the AAHP, the NCRP, and other scientific organizations. His formal education includes a BA degree in chemistry from Harvard University, an MS in industrial hygiene/radiological health from the Harvard School of Public Health, and a PhD in analytical chemistry from the University of Lowell. He is the author of numerous publications that include refereed journal articles, book chapters, reports, and manuals dealing with various aspects of radiation science and protection, especially in areas of radiation dosimetry and radiation measurement.

Medical and Dental Equipment/Shielding

Kenneth Duke LovinsKennith "Duke" Lovins is a medical health physicist and is certified by the ABHP. He has an MS degree in health physics from the University of Cincinnati and a BHS degree in radiological health science from the University of Kentucky. He has been employed by Unicon Physics, Inc., in Cincinnati, Ohio, since 1995 and provides consulting services to hospitals and clinics. His responsibilities include performing nuclear medicine department audits, developing quality-assurance programs for diagnostic radiology departments, performing quality-control testing on x-ray equipment, and providing training and membership on a number of radiation safety committees. Previously, he was a health physicist at the VA Medical Center in Lexington, Kentucky. He is a member of the HPS, the American Association for Physicists in Medicine (AAPM), the Conference of Radiation Control Program Directors, and the Cincinnati Radiation Society. He was a member of the joint HPS/AAPM working group to develop an ANSI standard for fetal radiation dose calculations.

Medical and Dental Patient Issues

Kent Lambert received his undergraduate degree in radiation protection engineering from Texas A&M University and his master's degree in radiation sciences from Rutgers University. He spent several years in industry before changing career paths and has over 25 years of experience at academic/medical institutions. Currently he is the director of regulatory compliance and radiation safety officer for Drexel University in Philadelphia. He also teaches (or has taught) physics courses to radiology technologist students and undergraduate and graduate courses in health physics, and he is a guest lecturer in numerous other courses. He has a faculty appointment as a senior instructor in the Department of Radiation Oncology. He is also the radiation safety officer for St. Christopher's Hospital for Children and Shriners Hospitals for Children–Philadelphia. For several years he was the consulting radiation safety officer for Hahnemann University Hospital, the Medical College of Pennsylvania, Cancer Treatment Centers of America at Eastern Regional Medical Center, and Woman's Medical Hospital and provided consulting health physics services to five other Tenet hospitals in Philadelphia.  

Kent is a fellow member of the HPS and is certified by the ABHP. He served on the HPS Board of Directors as a director and as treasurer. He was the Society's parliamentarian and served on various committees. He served on and chaired the ABHP Part I Exam Panel and was appointed to the ABHP, which he chaired in 2011. He has served two terms as president of the Delaware Valley Society for Radiation Safety.

Medical and Dental Patient Issues

Steven King received an undergraduate degree in environmental biology and teaching and a master's degree in radiation protection from the University at Buffalo. He became an assistant health physicist at the Penn State Hershey Medical Center in 1983 and has remained there for 32 years, currently serving as director of health physics. He has a faculty appointment as a senior instructor at Hershey Medical Center, where he is an imaging physicist and teaches radiation physics courses to radiology residents.

Steve is a fellow of the HPS and is certified by both the ABHP and the American Board of Medical Physics. He has been a member of the HPS Board of Directors and has served on a number of the Society's committees. He has also served as the president of the HPS Medical Section and is an associate editor of Operational Radiation Safety. Steve served for two terms as president of the Susquehanna Valley Chapter of the HPS.

In addition to his HPS activities, Steve is a member of the AAPM.

Nuclear Power, Devices, and Accidents

Joel Cehn is a native of Waterbury, Connecticut. He received his bachelor of science degree in physics from Worcester Polytechnic Institute in Massachusetts and a master of science degree in engineering from North Carolina State University. As an independent, board-certified health physicist, Joel measures radiation levels around nuclear power plants, research laboratories, and hospitals and at many varied locations in the United States and abroad. His work involves measurements of radioactivity in soil and groundwater, as well as measuring and estimating radiation doses to workers and the public. He has written and spoken extensively on exposure to radiation and its effects and has conducted numerous training sessions. He has served as an expert witness in several cases involving radiation and, in his spare time, creates educational kits for teaching about radiation. Joel lives in Central California and is past president of the local HPS chapter.

Nuclear Medicine Patient Issues

Marcia Hartman was a medical health physicist at the University of California Davis Medical Center (UCDMC) prior to taking her job as the HPS Web Operations Society operations editor. She has an MS in health physics from the University of Florida, where she was inspired to become a health physicist by her professors, HPS "Ask the Experts" Editor Gen Roessler, Chuck Roessler, and Emmett Bolch. She has 20 years of experience at UCDMC (an academic medical center) and was involved in all aspects of clinical and research use of radiation, including diagnostic and therapeutic machines, radiopharmaceuticals, and radioactive materials. Prior to that, Marcia worked in radiation protection programs in the nuclear power industry for 10 years. She has been involved in radiological emergency medical response planning in the nuclear power and hospital environments.

Policy, Guidelines, Standards, Regulations

Margaret Cervera came to health physics accidentally after a winding career path that included work in the service industry and veterinary medicine, as well as stints as a research microbiologist, pharmaceutical chemist, and cell biologist. Her formal education includes a BS in microbiology and chemistry with a certificate in biotechnology from Colorado State University. She went on to complete her master's degree in health physics at Colorado State University, serving along the way as president of the student chapter of the HPS. Upon graduation in 2009, Margaret quit her job as a forklift driver loading beer at the Anheuser-Busch brewery and reported for duty as a staff health physicist at the NRC. Her professional specialty is physical security of byproduct materials, but occasionally she has branched out into nuclear reactor regulation.

Pregnancy and Radiation

Robert Brent, MD, PhD, is the Distinguished Louis and Bess Stein Professor of Pediatrics, Radiology, and Pathology and head of the Clinical and Environmental Teratology Laboratory at Jefferson Medical College and A.I. duPont Hospital for Children. He obtained all of his degrees from the University of Rochester and did his pediatric training at Massachusetts General Hospital. He was chief of radiation biology at the Walter Reed Army Institute of Research and in 1957 came to Jefferson, where he has been primarily involved in research dealing with the causes and prevention of birth defects and reproductive problems. He has authored over 510 publications, including six books, and has made four movies. He belongs to 15 scientific societies, was one of the founding members and president of the Teratology Society, and was editor of the journal Teratology for 17 years. He was chairman of the Department of Pediatrics for 30 years, and during that period, his research was continuously funded by the National Institutes of Health. He has received many honors, including every award offered by his medical school, the most coveted of which was his selection as the third Distinguished Professor in Jefferson's 175-year history. He is a member of the Institute of Medicine of the National Academy of Sciences. His university has further honored him by creating the Robert L. Brent Professorship for the chairman of pediatrics at Jefferson and at the A.I. duPont Hospital for Children in Wilmington, where Brent's laboratory is now located. The HPS honored him in 2000 with the Robley Evans Award for his lifelong accomplishments in the field of radiation biology and for the counseling that he provides women of reproductive age with regard to the reproductive risks of radiation and other environmental exposures.

Radiation Safety Careers

Richard BreyRichard Brey is a full professor and director of the Health Physics Program at Idaho State University (ISU). Additionally, he serves as the director of the Environmental Assessment Laboratory at ISU. He holds an AAS degree in nuclear power technology from Terra Technical College. He also holds BS, MS, and PhD degrees in health physics from Purdue University. While at Purdue University, Richard was an Environmental Restoration and Waste Management fellow, an HPS Fellowship recipient, and an Institute of Nuclear Power Operations graduate fellow. Prior to this, he worked in applied health physics at the Donald C. Cook Nuclear Power Station in Bridgman, Michigan. He is a member of the HPS, the American Nuclear Society, and the American Conference of Governmental Industrial Hygienists. He has served as secretary and also as a president of the Eastern Idaho Chapter of the HPS. He is certified by the ABHP.

Radiation Workers/Pregnancy and Radiation

Kelly Classic, ATE associate editor and Web Operations deputy editor in chief, is a medical health physicist at Mayo Clinic Rochester and is certified by the American Board of Medical Physics. She has an MS degree in health physics and a BS degree in environmental health from Purdue University. She also has an MA degree in organizational management from Concordia University in St. Paul, Minnesota. In 1984 Classic was brought to Mayo Clinic Rochester as the assistant radiation safety officer and later also became the secretary to the organizational Radiation Safety Committee and Radioactive Drug Research Committee. She has been active in the HPS since 1984, serving on several committees, as section president for the RSO Section, and as a member of the Board of Directors. She has also held the position of president for the North Central Chapter of the HPS and participated on the Local Arrangements Committee for that chapter when an annual meeting was held in Minneapolis. In addition to her activities with the "Ask the Experts" website, she is an associate editor for the Society publication Operational Radiation Safety and is a council member of the NCRP.


Fred BaesFred Baes received a BS in biology at the University of Tennessee in 1972 and an MS in biology at Emory University in 1977. He then began a career at ORNL, where initially he developed computer codes, models, and data bases for assessing doses from radionuclides and risks from hazardous chemicals through terrestrial food-chain pathways. Later he became involved in air-pollution studies and explored the use of chemical analysis of tree rings as biomonitors for trace metal pollution and the effects of air pollution and acid deposition on forests. He later became a regulatory analyst and training instructor for the DOE, developing workshops on environmental laws and regulations and serving as editor of two newsletters on environmental laws and regulations. This latter work eventually evolved into an Internet-based effort, and Fred is now the webmaster for the DOE Office of Environmental Policy and Guidance website. In 1999 Fred became the webmaster for the HPS.

Editorial Associates

Sharon Hebl    Linnea
Sharon Hebl    Linnea Wahl