Leading experts in RF dosimetry dissect the pain of 5G—and the difference between exposure and dose
Kenneth R. Foster has decades of experience studying radio frequency (RF) radiation and its effects on biological systems.Now, he has co-authored a new survey on the topic with two other researchers, Marvin Ziskin and Quirino Balzano.Collectively, the three of them (all tenured IEEE fellows) have more than a century of experience on the subject.
The survey, published in the International Journal of Environmental Research and Public Health in February, looked at the past 75 years of research into RF exposure assessment and dosimetry.In it, the co-authors detail how far the field has advanced and why they consider it a scientific success story.
IEEE Spectrum spoke via email with University of Pennsylvania professor emeritus Foster.We wanted to learn more about why RF exposure assessment studies are so successful, what makes RF dosimetry so difficult, and why public concerns about health and wireless radiation never seem to go away.
For those unfamiliar with the difference, what is the difference between exposure and dose?
Kenneth Foster: In the context of RF safety, exposure refers to the field outside the body, and dose refers to the energy absorbed within the body tissue.Both are important for many applications - for example, medical, occupational health, and consumer electronics safety research.
"For a good review of research on the biological effects of 5G, see [Ken] Karipidis' article, which found 'no conclusive evidence that low-level RF fields above 6 GHz, such as those used by 5G networks, are harmful to human health.' "" -- Kenneth R. Foster, University of Pennsylvania
Foster: Measuring RF fields in free space is not a problem.The real problem that arises in some cases is the high variability of RF exposure.For example, many scientists are investigating RF field levels in the environment to address public health concerns.Considering the large number of RF sources in the environment and the rapid decay of the RF field from any source, this is not an easy task.Accurately characterizing individual exposure to RF fields is a real challenge, at least for the few scientists who attempt to do so.
When you and your co-authors wrote your IJERPH article, was your goal to point out the successes and dosimetric challenges of exposure assessment studies?Foster: Our goal is to point to the remarkable progress that exposure assessment research has made over the years, which has added a lot of clarity to the study of the biological effects of radio frequency fields and has driven major advances in medical technology.
How much has the instrumentation in these areas improved?Can you tell me what tools were available to you at the start of your career, for example, compared to what's available today?How do improved instruments contribute to the success of exposure assessments?
Foster: Instruments used to measure RF fields in health and safety research are getting smaller and more powerful.Who would have thought a few decades ago that commercial field instruments would become robust enough to be brought to the workplace, capable of measuring RF fields strong enough to cause an occupational hazard, yet sensitive enough to measure weak fields from distant antennas?At the same time, determine the precise spectrum of a signal to identify its source?
What happens when wireless technology moves into new frequency bands—for example, millimeter and terahertz waves for cellular, or 6 GHz for Wi-Fi?
Foster: Again, the problem has to do with the complexity of the exposure situation, not the instrumentation.For example, high-band 5G cellular base stations emit multiple beams that move through space.This makes it difficult to quantify exposure to people near cell sites to verify that exposure is safe (as they almost always are).
“I am personally more concerned about the possible impact of too much screen time on child development and privacy issues.” – Kenneth R. Foster, University of Pennsylvania
If exposure assessment is a solved problem, what makes the jump in accurate dosimetry so difficult?What makes the first so much simpler than the latter?
Foster: Dosimetry is more challenging than exposure assessment.You generally cannot insert an RF probe into someone's body.There are many reasons why you might need this information, such as in hyperthermia treatments for cancer treatment, where tissue must be heated to precisely specified levels.Heat too little and there is no therapeutic benefit, too much and you'll burn the patient.
Can you tell me more about how dosimetry is done today?If you can't insert a probe into someone's body, what's the next best thing?
Foster: It's OK to use old-fashioned RF meters to measure fields in air for a variety of purposes.This is of course the case with occupational safety work, where you need to measure the radio frequency fields that occur on workers' bodies.For clinical hyperthermia, you may still need to string patients with thermal probes, but computational dosimetry has greatly improved the accuracy of measuring thermal doses and has led to important advances in the technology.For studies of RF biological effects (for example, using antennas placed on animals), it is critical to know how much RF energy is absorbed in the body and where it goes.You can't just wave your phone in front of an animal as a source of exposure (but some investigators do).For some major studies, such as the recent National Toxicology Program study of lifetime exposure to RF energy in rats, there is no real alternative to computed dosimetry.
Why do you think there are so many ongoing concerns about wireless radiation that people measure levels at home?
Foster: Risk perception is a complex business.The characteristics of radio radiation are often cause for concern.You can't see it, there's no direct link between exposure and the various effects that some people worry about, people tend to confuse radio frequency energy (non-ionizing, meaning its photons are too weak to break chemical bonds) with ionizing X-rays, etc. Radiation (really dangerous).Some believe they are "overly sensitive" to wireless radiation, although scientists have been unable to demonstrate this sensitivity in properly blinded and controlled studies.Some people feel threatened by the ubiquitous number of antennas used for wireless communications.The scientific literature contains many health-related reports of varying quality through which one can find a scary story.Some scientists believe there may indeed be a health problem (though the health agency found they had little concern but said "more research" was needed).The list goes on.
Exposure assessments play a role in this.Consumers can buy inexpensive but very sensitive RF detectors and investigate RF signals in their environment, of which there are many.Some of these devices "click" as they measure radio frequency pulses from devices such as Wi-Fi access points, and will sound like a Geiger counter in a nuclear reactor for the world.scary.Some RF meters are also sold for ghost hunting, but this is a different application.
Last year, the British Medical Journal published a call to halt 5G deployments until the safety of the technology was determined.What do you think of these calls?Do you think they will help inform the segment of the public concerned about the health effects of RF exposure, or cause more confusion?Foster: You're referring to an opinion piece by [epidemiologist John] Frank, and I disagree with most of it.Most health agencies that have reviewed the science have simply called for more research, but at least one — the Dutch health board — has called for a moratorium on the rollout of high-band 5G until more safety research is done.These recommendations are sure to attract public attention (although HCN also considers it unlikely that there are any health concerns).
In his article, Frank writes, "The emerging strengths of laboratory studies suggest the [radio-frequency electromagnetic fields] destructive biological effects of RF-EMF."
That's the problem: there are thousands of RF biological effects studies in the literature. Endpoints, relevance to health, study quality and exposure levels varied widely.Most of them reported some kind of effect, at all frequencies and all exposure levels.However, most studies were at significant risk of bias (insufficient dosimetry, lack of blinding, small sample size, etc.) and many studies were inconsistent with others."Emerging research strengths" don't make much sense for this obscure literature.Frank should rely on closer scrutiny from health agencies.These have consistently failed to find clear evidence of adverse effects of ambient RF fields.
Frank complained about the inconsistency in publicly discussing "5G" -- but he made the same mistake by not mentioning frequency bands when referring to 5G.In fact, low-band and mid-band 5G operates at frequencies close to current cellular bands and does not appear to present new exposure issues.High-band 5G operates at frequencies slightly below the mmWave range, starting at 30 GHz.Few studies have been done on biological effects in this frequency range, but the energy barely penetrates the skin, and health agencies have not raised concerns about its safety at common exposure levels.
Frank didn't specify what research he wanted to do before rolling out "5G," whatever he meant.The [FCC] requires licensees to adhere to its exposure limits, which are similar to those in most other countries.There is no precedent for a new RF technology to be directly assessed for RF health effects before approval, which may require an endless series of studies.If the FCC restrictions are not safe, they should be changed.
For a detailed review of 5G biological effects research, see [Ken] Karipidis' article, which found "there is no conclusive evidence that low-level RF fields above 6 GHz, such as those used by 5G networks, are harmful to human health. The review also called for more research.
The scientific literature is mixed, but so far, health agencies have found no clear evidence of health hazards from ambient RF fields.But to be sure, the scientific literature on mmWave biological effects is relatively small, with around 100 studies, and of varying quality.
The government makes a lot of money selling spectrum for 5G communications, and should invest some of it in high-quality health research, especially high-band 5G.Personally, I am more concerned about the possible impact of too much screen time on child development and privacy issues.
Are there improved methods for dosimetry work?If so, what are the most interesting or promising examples?
Foster: Probably the main advance is in computational dosimetry with the introduction of finite difference time domain (FDTD) methods and numerical models of the body based on high resolution medical images.This allows a very precise calculation of the body's absorption of RF energy from any source.Computational dosimetry has given new life to established medical therapies, such as hyperthermia used to treat cancer, and has led to the development of improved MRI imaging systems and many other medical technologies.
Michael Koziol is an associate editor at IEEE Spectrum, covering all areas of telecommunications.He is a graduate of Seattle University with a BA in English and Physics, and an MA in Science Journalism from New York University.
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Current role: Distinguished Adjunct Professor at UCLA; Retired President, CEO and CTO of BEI Technologies
Education: 1968, RCA College; B.S., 1969 and 1972, M.S., UCLA, both in Electrical Engineering; Ph.D., California Coast University, 1987
Heroes: In general, my father taught me how to learn, how to be human, and the meaning of love, compassion, and empathy; in art, Michelangelo; in science, Albert Einstein; in engineering In, Claude Shannon
Favorite music: In Western music, the Beatles, Rolling Stones, Elvis; Eastern music, Ghazals
Organization members: IEEE Life Fellow; US National Academy of Engineering; UK Royal Academy of Engineering; Canadian Academy of Engineering
Most meaningful award: IEEE Medal of Honor: "Pioneering contributions to the development and commercialization of innovative sensing and systems technologies, and outstanding research leadership"; UCLA Alumni of the Year 2004
Madni received the 2022 IEEE Medal of Honor for pioneering GyroChip, among other contributions in technology development and research leadership.
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"I want to be an engineer who can invent things," Madeney said, "and do things that will ultimately impact humans. Because if I can't impact humans, I feel like my career will be unfulfilled."
Madni entered UCLA in 1969 with a bachelor's degree in electrical engineering after two years in the Electronics Technology program at RCA College.He went on to pursue a master's and a doctorate, using digital signal processing and frequency domain reflectometry to analyze telecommunication systems for his thesis research.During his studies, he also worked as a lecturer at Pacific State University, worked in inventory management at Beverly Hills retailer David Orgell, and as an engineer designing computer peripherals at Pertec.
Then, in 1975, newly engaged and at the insistence of a former classmate, he applied for a job in Systron Donner's microwave department.
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Post time: Apr-18-2022