Showing posts with label NTP. Show all posts
Showing posts with label NTP. Show all posts

Tuesday, August 11, 2026

NTP Cellphone Carcinogenicity Study: Followup Studies

Flawed "Validation" Studies Do Not Negate Established Evidence 
That Cell Phone Radiation Causes Cancer in Rats

Summary: A new paper published in Environmental Health finds that the Japanese and Korean cell phone radiation cancer studies do not prove cell phone safety, as they were underpowered and used too few exposure doses to legitimately challenge the U.S. National Toxicology Program’s landmark findings of increased cancer from long-term cell phone radiation exposure. Long-overdue policy changes to reduce public exposure are urgently needed.

A new peer reviewed paper published in the journal Environmental Health states that two industry-linked “validation” studies from Japan and Korea published in 2026, designed to verify the U.S. National Toxicology Program’s (NTP) finding that cell phone radiofrequency (RF) radiation causes cancer in rats, were so underpowered and narrowly designed such that they could never have confirmed or refuted the original results, regardless of the outcome. The authors state that these “validation” studies should not comfort the public when it comes to the safety of cell phones and other wireless devices.

The paper “Conflicting views in experimental carcinogenesis: A commentary on design and methodological deficiencies in the follow-up validation studies on radiofrequency radiation,” authored by Ronald L. Melnick (formerly of the National Institute of Environmental Health Sciences), Joel M. Moskowitz (University of California, Berkeley), and Paul Héroux (McGill University) on behalf of the International Commission on the Biological Effects of Electromagnetic Fields (ICBE-EMF), examines the design and interpretation of the Japan and Korea studies against long-standing scientific and regulatory standards for animal carcinogenicity testing.

Background

In 2011, the World Health Organization’s International Agency for Research on Cancer (IARC) classified RF radiation as “possibly carcinogenic to humans,” based largely on results from human epidemiological studies. In 2018, the National Toxicology Program, which is part of the U.S. Department of Health and Human Services, issued the final report of their $30 million animal studies concluding there is “clear evidence” that male rats exposed to cell phone (RF) radiation for two years developed malignant heart schwannomas, a rare tumor, along with “some evidence” of brain gliomas and adrenal tumors. The NTP study was designed to provide greater sensitivity than international guidelines for rigorous cancer-testing.

A study conducted by the Ramazzini Institute in 2018 reported increased tumors similar to those observed in the NTP. These new animal cancer findings, along with additional human studies, prompted the WHO/IARC advisory group to repeatedly recommend a new evaluation of the scientific evidence on the carcinogenicity of wireless radiation. Many scientists with expertise in environmental carcinogenicity then published their conclusion that the current evidence is now consistent with IARC criteria for the classification of wireless RF radiation as a “probable human carcinogen”  (IARC Group 2A), or even  “carcinogenic to humans” (Group 1).

However, after the NTP study was released, new animal studies were launched in Japan and Korea, under an “International Validation Project,” aiming to test whether the NTP’s findings were reproducible. Their results, separately published in 2026, concluded that long-term RF radiation exposure did not produce reproducible carcinogenic or genotoxic effects.

However, according to the new paper, the Japanese and Korean animal studies did not replicate the NTP study and had several deficiencies, including:

  • Severely Reduced Statistical Power: The follow-up studies used only 70 animals per group, compared to 90 per group in the NTP study. Power calculations indicate that detecting a significant response for rare tumors at the lower exposure level used in those studies would require many more animals per group.
  • Omission of High-Dose Groups: The follow-up studies tested only a single exposure level (4 W/kg) and dropped the NTP’s highest exposure level (6 W/kg), where significant carcinogenic effects were most statistically pronounced.
  • Violation of FDA and the Organization for Economic Co-operation and Development Guidelines: Testing guidelines by these groups require at least three different doses plus a control group to conduct a critical dose-response trend analysis. Single-dose studies eliminate the ability to detect dose-dependent trends.
  • Overlooked Signals of Harm: Despite being underpowered, the Korean study actually observed a 3% incidence rate of heart schwannomas in exposed rats (versus 0% in controls), matching the tumor rate observed at 3 W/kg in the NTP study, yet the researchers surprisingly dismissed the finding.
  • Prominent Role of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and Industry-Friendly Advisors: The project’s principal investigator was an ICNIRP member, and the advisory committee overseeing the research was heavily composed of current and former ICNIRP members, several of whom have served as industry consultants. The Japan/Korea studies were aimed at protecting ICNIRP’s current cell phone radiation safety limits rather than at documenting radiation risks.

The authors of the new analysis conclude that the Japan and Korea studies’ conclusion of “no reproducible carcinogenic potential” of cell phone radiation is simply not supported by the studies’ design and, in the case of the Korean study, is undercut by its own data. Therefore, the Japan and Korea studies do not alter the National Toxicology Program’s finding of “clear evidence” of cancer.

In a paper published earlier this year, Melnick and Moskowitz concluded that, based on the NTP cancer findings, current FCC and ICNIRP exposure limits would need to be at least 200 times lower to protect against cancer risk from 8 hours of daily exposure. The International Commission on the Biological Effects of Electromagnetic Fields is calling on governments to implement policies that reduce public exposure and inform cell phone users on how to minimize their risk.

Ronald L. Melnick, PhD, lead author and retired toxicologist at the National Institute of Environmental Health Sciences, who led the design of the original NTP radiofrequency radiation studies:

“The Japan and Korea studies cannot be used as proof of safety. To properly verify a study that found clear evidence of rare tumors like heart schwannomas, follow-up research must be designed with equal or greater sensitivity. By dropping the highest exposure level, testing only a single dose, and using fewer animals, these follow-up underpowered studies failed to meet basic FDA and OECD testing guidelines and were systematically biased toward finding no significant effect. These studies appear to be engineered to come back negative, no matter what the true biology is.

In short, the Japan and Korea studies cannot be used to invalidate the National Toxicology Program’s peer-reviewed findings of carcinogenicity or to justify the FCC’s and ICNIRP’s thermal-based exposure limits.”

Joel M. Moskowitz, PhD, School of Public Health, University of California, Berkeley, whose research focuses on the public health implications of wireless radiation exposure:

“Millions of people carry cell phones against their bodies for hours a day, and children are being exposed over far longer lifetimes than any generation before them. Public health decisions about safety limits should be built on the most rigorous animal evidence available, not on studies constructed in a way that was unlikely to detect harm even if it exists. We cannot allow flawed experimental designs to shield outdated safety guidelines from necessary, health-protective revisions. The scientific evidence on cancer and other biological effects is sufficient to warrant policies to reduce exposure.”

Dr. Paul Héroux, Department of Epidemiology, Biostatistics and Occupational Health, McGill University:

“These studies did not reproduce the original methodology, exposure assessment, or study conditions. From a biostatistical perspective, testing only 70 animals at a single dose level leaves a study severely underpowered to detect rare carcinogenic events. Without multiple dose groups and adequate sample sizes, finding ‘no statistically significant effect’ is an artifact of poor study design rather than evidence of safety. Importantly, when the NTP and Korean and Japanese studies are considered together, the overall evidence confirms cancer risk.” 

Implications for Public Policy and Public Health

The authors state that governments have a responsibility to protect public health by ensuring that exposure limits are based on the strongest available scientific evidence, not on studies that lack the scientific rigor necessary to detect known hazards. They conclude that the Japanese and Korean follow-up studies cannot be relied upon to dismiss the U.S. National Toxicology Program’s findings or to delay protective action. Before negative validation studies can be interpreted as evidence against the NTP’s findings, they must match or exceed the original study’s design, including the same animal model, exposure regimen, adequate group sizes, multiple exposure levels, and sufficient statistical power. Accordingly, they state that the WHO’s International Agency for Research on Cancer (IARC) and regulatory agencies should base hazard evaluations and public health policies on the strongest available evidence.

ICBE-EMF maintains that current U.S. and ICNIRP exposure limits for cell phones, Wi-Fi, smart meters, and cell towers are not adequately protective because a substantial body of research reports cancer and other biological effects, including DNA damage, oxidative stress, neurological effects, and reproductive harm. The Commission calls on governments to halt the rollout of new wireless technologies until independent safety assessments are completed and to adopt policies that reduce RF radiation exposure risks.

Scientific reference:

Melnick, R.L., Moskowitz, J.M., Héroux, P. et al. Conflicting views in experimental carcinogenesis: a commentary on design and methodological deficiencies in the follow-up validation studies on radiofrequency radiation. Environ Health 25, 66 (2026). https://doi.org/10.1186/s12940-026-01324-5

About the ICBE-EMF 

ICBE-EMF is an international consortium of scientists, doctors, and researchers with expertise and peer-reviewed publications on the biological and health effects of electromagnetic fields, including RF radiation. The Commission is committed to upholding the highest standards of scientific research and makes science-based recommendations to ensure the protection of the public and the environment. 

https://icbe-emf.org/flawed-validation-studies-do-not-negate-the-established-evidence-that-cell-phone-radiation-causes-cancer-in-rats-scientists-conclude/


Conflicting views in experimental carcinogenesis: a commentary on design and methodological deficiencies in the follow-up validation studies on radiofrequency radiation

Melnick RL, Moskowitz JM, Héroux P, on behalf of International Commission on the Biological Effects of Electromagnetic Fields. Conflicting views in experimental carcinogenesis: a commentary on design and methodological deficiencies in the follow-up validation studies on radiofrequency radiation. Environ Health 25, 66 (2026). https://doi.org/10.1186/s12940-026-01324-5.

Abstract

Conflicting views in experimental carcinogenesis often arise due to differences in study design among reported studies. For carcinogenicity assessments, regulatory agencies, such as the US Food and Drug Administration (FDA), and intergovernmental advisory organizations, such as the Organization for Economic Co-operation and Development (OECD), specify the use of at least three dose levels plus control group for trend analyses, with the highest dose inducing a measurable toxic response. In addition, there needs to be a sufficient number of animals per group to have adequate power to detect a true carcinogenic effect. Departure from such recommendations can weaken the interpretations of study results. We examine here two recent carcinogenicity studies from Japan and Korea that were conducted following the positive carcinogenicity study of radiofrequency radiation (RFR) in experimental animals by the National Toxicology Program (NTP). The Japan and Korea follow-up studies used fewer animals per group, a single RFR exposure group, and a lower exposure level than the NTP study. Not surprisingly, while the NTP study revealed the carcinogenicity of RFR, the Japanese and Korean studies, which had reduced statistical power compared to the NTP study, issued conclusions conflicting with those of the more substantial NTP study on the health effects of RFR. In general, carcinogenicity studies with weaker doses, fewer exposure groups, and reduced statistical power should not be used to test the validity of more robust studies.

Excerpt

Despite the numerous limitations in their study design, the authors of the Japan-Korea studies concluded there is “no reproducible carcinogenic potential of mobile phone-type RF exposure in rats,” and that alternatives to the ICNIRP “recommend[ed] exposure limits for RF radiation based on thermal effects” are inconclusive [3]. These statements reflect ideological support for ICNIRP’s thermal-only mechanism of adverse effects and its repeated dismissal of the validity of the NTP carcinogenicity studies (e.g [12]). The project’s principal investigator is a member of ICNIRP, and the advisory committee that provided oversight and guidance throughout this project was heavily represented by current and past members of ICNIRP, suggesting a strong influence of ICNIRP in the design and interpretation of these studies.

In conclusion, methodological shortcomings due to the design choices in the Japan–Korea studies, specifically the restriction to a single exposure group of 4 W/kg of CDMA-modulated RFR and reduced statistical power, systematically biased the study toward null results and eliminated the possibility of detecting a positive trend. Consequently, these findings cannot be used to reasonably refute the peer-reviewed evidence of toxicity and carcinogenicity of CDMA- and GSM-modulated RFR in the NTP studies, nor to reinforce ICNIRP’s thermal-based exposure limits. It is also important to note that the increases in schwannomas and gliomas reported in experimental studies of RF-EMF are of the same tumor types (glioma and vestibular schwannoma) that were increased in epidemiological studies in which brain cancer risk was increased among heavy users of mobile phones [13]. The example described in this commentary demonstrates how limited and divergent experimental designs and potential biases in the interpretation of experimental carcinogenicity results can lead to conflicting views on the health effects of RFR.

Open access: https://link.springer.com/article/10.1186/s12940-026-01324-5

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The International Collaborative Animal Study of Mobile Phone Radiofrequency Radiation Carcinogenicity and Genotoxicity

Imaida K, Kawabe M, Wang J, Yokohira M, Imai N, Han K-H, Kim Y-B, Jeon SB, Kim HY, Ahn YH.The International Collaborative Animal Study of Mobile Phone Radiofrequency Radiation Carcinogenicity and Genotoxicity: The Japanese Study. Toxicol Sci. 2026. 1/13/26. https://doi.org/10.1093/toxsci/kfag002.

Abstract

The potential carcinogenic and genotoxic effects of radiofrequency electromagnetic fields, particularly those emitted by mobile communication systems, have raised public health concerns. A previous study by the U.S. National Toxicology Program suggested increased incidences of gliomas and cardiac schwannomas in rats exposed to high levels of RF radiation. To evaluate these findings, an international collaborative study was initiated between Japan and Korea.

Male Hsd:Sprague Dawley® SD® rats were exposed to 900 MHz CDMA-modulated RF-EMFs at a whole-body specific absorption rate of 4 W/kg for 18 hours and 20 minutes daily over two years. The study included a 28-day preliminary toxicity study, genotoxicity assays (alkaline comet and micronucleus tests), and a two-year carcinogenicity assessment. All procedures followed OECD guidelines and Good Laboratory Practice. No statistically significant increases in the incidences of neoplastic or non-neoplastic lesions were found in any major organ, including the brain, heart, and adrenal glands. Genotoxicity assays revealed no evidence of DNA damage or chromosomal aberrations in RF-exposed rats. A higher survival rate in the RF-exposed group, likely due to lower body weight and food consumption, was observed.

This study performed in Japan, jointly planned and executed by Japan and Korea, provides strong evidence that long-term exposure to 900 MHz RF-EMFs did not produce reproducible carcinogenic or genotoxic effects in male rats. Combined with data from the Korean counterpart study, these results are expected to contribute to future international assessments of the carcinogenic potential of electromagnetic radiation.

Open access: https://academic.oup.com/toxsci/article/209/3/kfag002/8423504

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The International Collaborative Animal Study of The Carcinogenicity and Genotoxicity of Mobile Phone Radiofrequency Radiation: The Korean Study

Kim HS, Han KH, Kim YB, Jeon SB, Lee AK, Moon JI, Choi HD, Imaida K, Yokohira M, Kawabe M, Imai N, Wang J, Ahn YH. The International Collaborative Animal Study of The Carcinogenicity and Genotoxicity of Mobile Phone Radiofrequency Radiation: The Korean Study. Toxicol Sci. 2026 Jan 16:kfag001. doi: 10.1093/toxsci/kfag001. 

Abstract

A chronic bioassay investigating radiofrequency (RF) carcinogenicity, intentionally designed to be conducted simultaneously in Korea and Japan, using the same research protocol and experimental environment. The study aimed to assess the potential carcinogenicity of Code Division Multiple Access (CDMA)-modulated 900 MHz RF signals at a whole-body specific absorption rate (SAR) of 4 W/kg, which is the reference level of the international human safety guideline, and to verify the key findings from the National Toxicology Program (NTP) study at that SAR level. Two reverberation chamber systems were used for RF exposures, and the same study protocols were followed. Male Harlan Sprague-Dawley (Hsd: Sprague Dawley® SD®) rats were randomly assigned to cage-control, sham-exposed, or RF-exposed groups. The exposure started on gestational day 5 and lasted for 18 hours and 20 minutes each day, with 10-minute on/off cycles. The project included a 28-day toxicity study, a 2-year carcinogenicity study, and a 14-week genotoxicity test. Histopathological evaluations were conducted in a partially blinded manner. The results were independently analyzed and submitted separately based on each country's research findings. In the Korean study, no statistically significant changes in tumor incidence or survival rates were observed. No significant RF-related effects were detected in the heart, brain, or adrenal glands. No changes in body temperature. Genotoxicity tests showed no evidence of DNA damage or mutation. In conclusion, the Korean part found that long-term exposure to CDMA-modulated 900 MHz RF was neither carcinogenic nor genotoxic at a SAR of 4 W/kg in male rats.

Open access: https://academic.oup.com/toxsci/article/209/3/kfag001/8428133

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An International Collaborative Animal Study of the Carcinogenicity of Mobile Phone Radiofrequency Radiation: Considerations for Preparation of a Global Project

Ahn YH, Imaida K, Kim YB, Han KH, Pack JK, Kim N, Jeon SB, Lee AK, Choi HD, Wang J, Kawabe M, Kim HS. An International Collaborative Animal Study of the Carcinogenicity of Mobile Phone Radiofrequency Radiation: Considerations for Preparation of a Global Project. Bioelectromagnetics. 2022 May;43(4):218-224. doi: 10.1002/bem.22407. 

Abstract

Radiofrequency radiation (RFR) was classified as a "possible" human carcinogen in 2011, which caused great public concern. A carcinogenicity study by the National Toxicology Program (NTP) found Code Division Multiple Access-and Global System for Mobile Communications-modulated mobile phone RFR to be carcinogenic to the brain and heart of male rats. As part of an investigation of mobile phone carcinogenesis, and to verify the NTP study results, a 5-year collaborative animal project was started in Korea and Japan in 2019. An international animal study of this type has two prerequisites: use of the same study protocol and the same RF-exposure system. This article discusses our experience in the design of this global study on radiofrequency electromagnetic fields (RF-EMFs).

Open access: https://onlinelibrary.wiley.com/doi/10.1002/bem.22407

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Wednesday, May 13, 2026

Wireless Radiation Exposure Limits


Maximum recommended radio frequency exposure levels
(power density) by source


For the general public, the recommended maximum whole-body average radio frequency exposure limit as measured by the incident power density varies by source:

FCC (based on acute heating averaged over 30 minutes)

https://www.rfcafe.com/references/electrical/fcc-maximum-permissible-exposure.htm

Recommended levels:

2,000,000 µW/m2 (for 30 - 300 MHz)

frequency (in Hz)/150 µW/m2 (for 300 MHz - 1500 MHz)

10,000,000 µW/m2 (for 1500 MHz - 100,000 MHz)


ICNIRP (2020) (based on acute heating averaged over 30 minutes)

https://www.icnirp.org/cms/upload/publications/ICNIRPrfgdl2020.pdf

Recommended levels:

2,000,000 µW/m2 (for 30 - 400 MHz)

frequency (in Hz)/200 µW/m2 (for 400 MHz - 2000 MHz)

10,000,000 µW/m2 (for 2000 MHz - 300,000 MHz)

 
China


400,000 µW/m2


Russia


100,000 µW/m2


Council of Europe, Resolution 1815

https://assembly.coe.int/nw/xml/XRef/Xref-XML2HTML-en.asp?fileid=17994

Recommended level: 106 µW/m2


European EMF guideline for the prevention, diagnosis and treatment of EMF-related health problems and illnesses.(Belyaev et al,, 2016)

https://www.degruyter.com/document/doi/10.1515/reveh-2016-0011/html?lang=en

Recommended levels:

FM radio: 100 - 10,000 µW/m2

Cell phone frequencies: 1 - 100 µW/m2

Wi-Fi (2400 and 5000 MHz): 0.1 - 10 µW/m2


BioInitiative Report (2012)

https://bioinitiative.org/wp-content/uploads/pdfs/section_1_table_1_2012.pdf

Recommended levels: 3–6 µW/m2


Building Biology Institute guideline for sleeping areas (2015)

https://static1.squarespace.com/static/55517edbe4b0b260d3936ec1/t/5e3ca9927d681d130c3c0364/1581033875399/SBM-2015_Building_Biology_Evaluation_Guideline_Values.pdf

Recommended level: <0.1 µW/m2


Definitions:

Mhz = megahertz = million cycles per second

µW/m2 = microwatts per square meter = millionths of a watt per square meter

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May 13, 2026

Exposure limits to radiofrequency EMF do not account for cancer risk or reproductive toxicity assessed from data in experimental animals

Melnick RL, Moskowitz JM, International Commission on the Biological Effects of Electromagnetic Fields (ICBE-EMF). Exposure limits to radiofrequency EMF do not account for cancer risk or reproductive toxicity assessed from data in experimental animals. Environ Health. 2026 Mar 14. doi: 10.1186/s12940-026-01288-6.

Abstract

Background  Recent WHO-commissioned systematic reviews have concluded with “high certainty” that exposure to radiofrequency electromagnetic fields (RF-EMF) increases cancer risk and reduces male fertility in experimental animals.

Methods  We performed benchmark dose (BMD) analyses on experimental cancer data to estimate exposure levels associated with cancer risk of 1 × 10–5 (1 in 100,000). Due to the lack of an established non-linear mode of action for RF-EMF-induced tumor responses, we utilized linear low-dose extrapolation from 1% BMD values. In addition, we applied traditional uncertainty factors to the reported linear potency value of 0.03 per W/kg for male reproductive toxicity to derive health-protective exposure limits.

Results  The derived dose per hour (expressed as the specific absorption rate, SAR) at 1 × 10–5 cancer risk ranges from about 0.8 to 5 mW/kg. It should be noted that cancer risk increases with increasing time of exposure to RF-EMF. For protection of male fertility due to exposure to RF-EMF, the estimated SAR exposure limit was 3.3 to 10 mW/kg. These health protective whole-body exposure values are significantly lower than the current whole-body exposure limit value of 0.08 W/kg (80 mW/kg) established by ICNIRP and the FCC for the general public.

Conclusions  For the general public, current regulatory limits to RF-EMF are 15- to 900-fold higher than our estimates of exposure levels associated with cancer risk of 1 × 10–5 (depending on the duration of daily exposure), and 8- to 24-fold higher than levels that are protective of male reproductive health. Thus, we strongly recommend an independent re-evaluation of RF-EMF exposure limits, integrating scientific data accumulated over the past 30 years and applying rigorous health-protective methodologies.


1 x 10-5 = excess risk of 1 per 100,000 persons
     W/kg = watts per kilogram of tissue
  mW/kg = milliwatts per kilogram of tissue

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April 19, 2022


Leading experts on wireless radiation biological effects call for stronger exposure limits in new research review

On April 19, Dr. Henry Lai and B. Blake Levitt published an extensive review of the research on the biological effects of wireless radiation which calls for stronger limits on radio frequency radiation exposure to protect human health. According to their paper, governments should adopt a maximum full-body Specific Absorption Rate (SAR) of 1.65 milliwatts per kilogram which is 48 times lower than the wireless exposure limits that allow the public to be exposed to a full-body SAR of 80 milliwatts per kilogram and 960 times lower than the 1.6 watts per kilogram cell phone exposure limit for the head and torso in the U.S. The paper was published in the peer-reviewed journal, Electromagnetic Biology and Medicine (see abstract and excerpts below).

Dr. Lai is professor emeritus at the University of Washington. In his long research career he has focused on the biological effects of non-ionizing electromagnetic fields and their possible medical applications with research end points covering molecular biology, neurochemistry, behavior, and cancer treatment. He has published over 100 peer-reviewed research papers.


Lai H, Levitt BB. The roles of intensity, exposure duration, and modulation on the biological effects of radiofrequency radiation and exposure guidelines. Electromagn Biol Med. 2022 Apr 3;41(2):230-255. doi: 10.1080/15368378.2022.2065683.

Abstract

In this paper, we review the literature on three important exposure metrics that are inadequately represented in most major radiofrequency radiation (RFR) exposure guidelines today: intensity, exposure duration, and signal modulation. Exposure intensity produces unpredictable effects as demonstrated by nonlinear effects. This is most likely caused by the biological system’s ability to adjust and compensate but could lead to eventual biomic breakdown after prolonged exposure. A review of 112 low-intensity studies reveals that biological effects of RFR could occur at a median specific absorption rate of 0.0165 W/kg. Intensity and exposure duration interact since the dose of energy absorbed is the product of intensity and time. The result is that RFR behaves like a biological “stressor” capable of affecting numerous living systems. In addition to intensity and duration, man-made RFR is generally modulated to allow information to be encrypted. The effects of modulation on biological functions are not well understood. Four types of modulation outcomes are discussed. In addition, it is invalid to make direct comparisons between thermal energy and radiofrequency electromagnetic energy. Research data indicate that electromagnetic energy is more biologically potent in causing effects than thermal changes. The two likely function through different mechanisms. As such, any current RFR exposure guidelines based on acute continuous-wave exposure are inadequate for health protection.

Excerpts

"Over the last 25–30 years, significant information has been published that in other regulated areas would have resulted in re-examination and adjustments to allowable exposure limits. This has not been the case with these two groups [the FCC and ICNIRP] which adhere to a model based on obsolete scientific evidence, especially in light of the new 5G network that uses higher frequencies and novel modulation forms that have never been used before in broad civilian telecommunications and which are poorly studied."

"RFR effects have been observed at low intensities (< 0.4 W/kg) – a list of which is included in Supplement 1 – far below the guidelines. This points to both the nonlinearity of how living systems couple with nonionizing radiation as well as the inadequacy of acute thresholds. The studies encompass many different biological effects to myriad systems, including: apoptosis induction, adrenal gland activity, blood–brain barrier permeability, brain transmitter levels, calcium concentration in heart muscle, calcium efflux, calcium movement in cells, cell growth, cognitive functions, cellular damage in liver, decreased cell proliferation, embryonic development, endocrine changes, enolose activity, genetic effects, hippocampal neuronal damage, immunological functions, kidney development, memory functions, latency of muscular contraction, membrane chemistry, nerve cell damage, metabolic changes, neural electrical activity, oxidative stress, plant growth, prion level, protein changes, renal injury, serum testosterone concentration, heat-shock protein induction, testis morphology, testosterone synthesis, thymidine incorporation, and ultrastructural alteration in cell cytoplasm. In fact, there are not many physiological functions in humans, animals, or plants that are not affected by low-level RFR."

"As reflected in Supplement 1, SARs at which effects were observed were available from 112 studies. Of these, 75 (67%) were in vivo exposure studies with whole body/organ SARs available. The other 37 (33%) studies were in vitro experiments.... The level at which biological effects occur represents data from in vivo and in vitro and acute and chronic/repeated-exposure experiments. There is a very wide range of effects seen. With an exposure that induces a SAR of 0.0165 W/kg, and using a ten-fold protection, the SAR would be 0.00165 W/kg (i.e., 1.65 mW/kg). For rate of energy absorption in body organs, 0.00165 W/kg is far below the maximum level allowed in the guidelines (whether over 1 or 10 gm of tissue as per FCC/ICNIRP allowances). Given the large body of work as illustrated in Supplement 1, the SAR at, or below, 4 W/kg as a safe threshold is insupportable."

"The duration of exposure is another important factor in biological effects. Other than demarcations for whole body exposures averaged over 30 minutes and local body areas averaged over 6 minutes, neither FCC nor ICNIRP address duration, especially pertaining to long-term and low-level RFR exposures. These are prevalent in both near-field exposures to people with WiFi routers, for example, as well as cell phones, and far-field exposures from infrastructure that have created chronic rising ambient background levels (Levitt et al. 2021a). The guidelines are written only for short-term acute durations.... What we do know is that the supposition that all exposures are the same above and below the SAR threshold set by FCC/ICNIRP is fundamentally flawed in light of the most current research. One feasible and logical solution to such uncertainties regarding duration as an exposure factor would be to adopt an SAR level commensurate with the studies summarized in Supplement 1 at no higher than 0.00165 W/kg, no matter the exposure conditions."

"It is generally believed that modulated RFR is more biologically active than continuous-wave (CW) radiation, i.e., the carrier-wave. To understand the biological and possible hazardous health effects of RFR, it is therefore important to understand modulation effects. Below we discuss what is known about modulation from the research literature (mostly from 1990 to date) and examine the claim that modulation makes RFR more biologically significant...There is research showing no significant biological effects of CW-RFR (Table 1a) but there are also studies that reported CW-RFR effects too (Table 1b). The reason why CW-RFR produced effects in some studies but not others is unknown. Both types of studies (with “effect” and “no effect” outcomes) involved many different biological endpoints, exposure intensities, and duration of exposure – with no discernible differences. A possible explanation is that different tissue types respond differently to CW-RFR. But that just adds another level of inquiry. One of the most puzzling observations is when CW caused an effect but modulation did not (e.g., Kubinyi et al. 1996; Luukkonen et al. 2009). In some studies, a modulated field produced an effect that was not produced by CW. These observations may indicate that the CW carrier-wave itself and modulation act on different mechanisms.... Differences in responses between CW and modulated fields of the same frequency and incident power density provide strong proof that non-thermal effects occur since the two conditions should produce the same amount of heating.... Some studies reported that different frequencies of modulation caused different biological responses .... CW and modulated fields can cause the same effects but with different degrees of biological activity and intensity of reactions. In most instances, a modulated field was found to be more potent than CW versus only one study in which the opposite was reported (Persson et al. 1997).... To add to the complexities described above, effects with modulated fields have also been shown to depend on exposure duration.... there are many studies that used intermittent exposure (e.g., 10 min ON/10 min OFF) instead of continuous exposure with the supposition that intermittent exposure is more biologically active. But not much data showed this to be true.... There are many studies using pulsed fields (i.e., mobile phone signals are pulsed), but there are not many studies that compared pulsed and CW fields of the same SAR in the same study. However, there are reports that effects only occurred with a pulsed field but not CW.... there are many studies showing effects of RFR on the hippocampus..."

"Oxidative changes and stress have been reported in many papers on exposure to electromagnetic fields (Lai 2020; Yakymenko et al. 2016). These are the most consistent cellular responses to RFR exposure. Mechanisms have been proposed to account for oxidative effects that may involve the low-frequency component of modulation (e.g., see Barnes and Greenebaum 2015; Castello et al. 2021). ... But there is not enough data to conclude that modulation effects are caused by oxidative processes. In fact some effects of CW exposure alone also found changes in free radical mechanisms."

"It is important to point out as significant proof of non-thermal RFR effects that CW and modulated-waves of the same frequency and incident power density can/and do produce different effects. The bottom line is that certainty is elusive regarding precise effects in all circumstances. What is clear is that both modulation and continuous-wave RFR are biologically active and both should be considered in exposure guidelines. In situations where enough evidence exists to warrant specific caution, such as with pulsed fields used in cell phones and phased modulation with 5G, particular attention should be paid to include modulation in the guidelines beyond the suppositions of safety contained within the safety allowances. Peak exposures must also be factored in and not just the averaged values which only hide their significance."

"It is apparent that the biological outcome of changing the intensity and duration of RFR exposure is basically unpredictable. This is mainly due to the complex nature of the biological system studied. Intensity and duration can interact and produce different response patterns as shown in the literature reviewed above.

It is also apparent that how RFR modulation affects biological functions is difficult to quantify. Observed effects are multi-variant and involve many factors such as intensity, carrier frequencies and modulation, the modulation waveform itself, exposure duration, and properties of the exposed object. Not enough research data are presently available to provide an explanation or prediction of modulation effects under all circumstances. It may also turn out that modulation is of little major health concern or conversely that it is the only factor that matters – evidence is thus far too contradictory regarding modulation’s ability to consistently enhance the biological effects of carrier-waves. Then again, with most modulation forms the carrier-wave is completely altered. All of this awaits proper investigation with comparison studies. In the meantime, there are legitimate reasons for concern, given the contradictions in the literature.

In general, anthropogenic RFR – with highly unusual waveform characteristics and intensities that do not exist in the natural world – is new to the environment and thus has not been a factor in the evolution of species. Living organisms evolved over millions of years in the presence of static and extremely-low frequency (ELF) electromagnetic fields. These fields play critical roles in their survival, e.g., in migration, food foraging, and reproduction, etc. (see Levitt et al. 2021b). Living organisms are extremely sensitive to the presence of these environmental fields and thus, they can easily be disturbed by man-made EMF. RFR probably acts upon and modifies these primordial EMFs and affects biological functions. Interactions of static/ELF EMF and RFR are basically not well studied, not to mention the mechanisms of involvement of RFR modulations. The interactions are inevitably complex. Such interaction studies would provide answers to wildlife effects.

Regarding the perennial thermal- versus non-thermal- effects criticism inherent in human RFR exposure guidelines, it must be said that the underlying mechanisms of effects should not be a matter of concern in setting of exposure guidelines as is common today. What is important is the level at which energy absorption causes an effect. One such powerful proof – among so very many others – of non-thermal effects is evidenced in the fact that CW and modulated-waves of the same frequency and incident power density can produce different effects, as seen in the modulation section of this paper and Table 2."

"When effects continue to be observed over a long period of time that go against prevailing beliefs, even when mechanisms remain imperfectly understood, the appropriate course of regulatory action is to examine the underlying basis upon which an original premise was formed. When proven incomplete or invalid by new information, the change in a regulatory course is not only justified but is imperative. Disproven or incomplete deductions of how RFR affects living cells and tissues, as well as suppositions of safety for exposed individuals and the environment are insupportable given the wealth of studies to draw from today that have filled in many gaps. We need to more responsibly address the increasing near- and far-field RFR exposures of contemporary life with an eye toward 5G technology’s unique characteristics. A new conceptual framework is called for."


==


Study: Wireless radiation exposure for children should be hundreds of times lower than current federal limits

Environmental Working Group, July 2021

WASHINGTON – A peer-reviewed study by the Environmental Working Group recommends stringent health-based exposure standards for both children and adults for radiofrequency radiation emitted from wireless devices. EWG’s children’s guideline is the first of its kind and fills a gap left by federal regulators.

The study, published in the journal Environmental Health, relies on the methodology developed by the Environmental Protection Agency to assess human health risks arising from toxic chemical exposures. EWG scientists have applied the same methods to radiofrequency radiation from wireless devices, including cellphones and tablets.

EWG recommends the Federal Communications Commission, or FCC, adjust its woefully outdated health standards for wireless radiation, last revised a quarter-century ago, well before wireless devices became ubiquitous, heavily used appliances synonymous with modern life. The recommendation draws on data from a landmark 2018 study from the National Toxicology Program, or NTP, one of the largest long-term studies on the health effects of radiofrequency radiation exposure.

EWG’s new guidelines, the first developed in the U.S. to focus on children’s health, recommend that children’s exposure overall be 200 to 400 lower than the whole-body exposure limit set by the FCC in 1996.

The EWG recommended limit for so-called whole-body Specific Absorption Rate, or SAR, for children is 0.2 to 0.4 milliwatts per kilogram, or mW/kg. For adults, EWG recommends a whole-body SAR limit of 2 to 4 mW/kg, which is 20 to 40 times lower than the federal limit.

The FCC has not set a separate standard for children. Its standards for radiofrequency radiation set a maximum SAR of 0.08 watts per kilogram, or W/kg, for whole-body exposure and an SAR for localized spatial peak – the highest exposure level for a specific part of the body, such as the brain – of 1.6 W/kg for the general population.

The NTP studies examined the health effects of 2G and 3G wireless radiation and found there is “clear evidence” of a link between exposure to radiofrequency radiation and heart tumors in laboratory animals. Similar results were reported by a team of Italian scientists from the Ramazzini Institute.

Cellphone radiation was classified a “possible carcinogen” in 2011 by the International Agency for Research on Cancer, part of the World Health Organization, a conclusion based on human epidemiological studies that found an increased risk of glioma, a malignant brain cancer, associated with cellphone use.

EWG scientists say that more research is needed on the health impacts of the latest generation of communication technologies, such as 5G. In the meantime, EWG’s recommendation for strict, lower exposure limits for all radiofrequency sources, especially for children.

When the FCC established its radiofrequency radiation limits, following the passage of the 1996 Telecommunications Act, relatively few Americans, and likely no children, owned and used cellphones.

Much has changed since the federal limits were set, including technology and how these devices are used. A survey completed by the nonprofit Common Sense Media in March 2020, just before the start of the Covid-19 spread in the U.S., found that 46 percent of 2- to 4-year-olds, and 67 percent of 5- to 8-year-olds, had their own mobile devices, such as a tablet or smartphone.

With remote learning, a necessity during the Covid-19 pandemic, phones, tablets and other wireless devices became a part of life for young children, tweens and teens nationwide.

“The FCC must consider the latest scientific research, which shows that radiation from these devices can affect health, especially for children,” said Uloma Uche, Ph.D., EWG environmental health science fellow and lead author of the study.

“It has been 25 years since the FCC set its limits for radiofrequency radiation. With multiple sources of radiofrequency radiation in the everyday environment, including Wi-Fi, wireless devices and cell towers, protecting children’s health from wireless radiation exposures should be a priority for the FCC,” she added.

“We have grave concerns over the outdated approach the federal government has relied on to study the health effects of cellphone radiation and set its current safety limit and advice for consumers,” said EWG President Ken Cook. “Government guidelines are a quarter-century old and were established at a time when wireless devices were not a constant feature of the lives of nearly every American, including children.”

Reviewing 5G and other aspects of wireless technology should be the focus of public health agencies, noted Cook. “It is long past time the federal government made exposure to 5G wireless devices safe. We strongly believe those exposures deserve far more investigation and scientific rigor than has been applied to date.”

“The evidence shows that children absorb more radiofrequency radiation than adults, and the developing body of a child is more vulnerable to such effects,” said Olga Naidenko, Ph.D., EWG’s vice president for science investigations and co-author of the study.

“More research on the safety and sustainability of wireless technology is essential,” added Naidenko. “Meanwhile, there are simple steps everyone can take to protect their health, such as keeping wireless devices farther from their bodies.”

There are a number of easy, precautionary steps consumers can take until the government conducts the rigorous scientific assessment the issue deserves, which should have occurred years ago.

“Based on our review of the health risks and the inadequacy of current standards to protect children, while the science evolves, it is perfectly reasonable for parents to consider minimizing or eliminating radiofrequency radiation sources at home by relying more on wired internet access, and to urge schools to take comparable steps to reduce classroom and campus exposure,” said Cook.

Other health-protective tips for consumers who want to reduce radiofrequency radiation from wireless devices include using a headset or speaker, texting instead of talking, and limiting the time children spend on smart phones.

Find all of EWG’s tips to reduce exposure to wireless radiation here.

EWG’s recommendation for limits for radiofrequency radiation exposure is its latest effort to advance the public dialogue about science-based standards that protect public health.

https://www.ewg.org/news-insights/news-release/2021/07/study-wireless-radiation-exposure-children-should-be-hundreds


Development of health-based exposure limits for radiofrequency radiation from wireless devices using a benchmark dose approach

Uche UI, Naidenko OV. Development of health-based exposure limits for radiofrequency radiation from wireless devices using a benchmark dose approach. Environ Health. 2021 Jul 17;20(1):84. doi: 10.1186/s12940-021-00768-1.

Abstract

Background  Epidemiological studies and research on laboratory animals link radiofrequency radiation (RFR) with impacts on the heart, brain, and other organs. Data from the large-scale animal studies conducted by the U.S. National Toxicology Program (NTP) and the Ramazzini Institute support the need for updated health-based guidelines for general population RFR exposure.

Objectives  The development of RFR exposure limits expressed in whole-body Specific Absorption Rate (SAR), a metric of RFR energy absorbed by biological tissues.

Methods  Using frequentist and Bayesian averaging modeling of non-neoplastic lesion incidence data from the NTP study, we calculated the benchmark doses (BMD) that elicited a 10% response above background (BMD10) and the lower confidence limits on the BMD at 10% extra risk (BMDL10). Incidence data for individual neoplasms and combined tumor incidence were modeled for 5% and 10% response above background.

Results  Cardiomyopathy and increased risk of neoplasms in male rats were the most sensitive health outcomes following RFR exposures at 900 MHz frequency with Code Division Multiple Access (CDMA) and Global System for Mobile Communications (GSM) modulations. BMDL10 for all sites cardiomyopathy in male rats following 19 weeks of exposure, calculated with Bayesian model averaging, corresponded to 0.27–0.42 W/kg whole-body SAR for CDMA and 0.20–0.29 W/kg for GSM modulation. BMDL10 for right ventricle cardiomyopathy in female rats following 2 years of exposure corresponded to 2.7–5.16 W/kg whole-body SAR for CDMA and 1.91–2.18 W/kg for GSM modulation. For multi-site tumor modeling using the multistage cancer model with a 5% extra risk, BMDL5 in male rats corresponded to 0.31 W/kg for CDMA and 0.21 W/kg for GSM modulation.

Conclusion  BMDL10 range of 0.2—0.4 W/kg for all sites cardiomyopathy in male rats was selected as a point of departure. Applying two ten-fold safety factors for interspecies and intraspecies variability, we derived a whole-body SAR limit of 2 to 4 mW/kg, an exposure level that is 20–40-fold lower than the legally permissible level of 0.08 W/kg for whole-body SAR under the current U.S. regulations. Use of an additional ten-fold children’s health safety factor points to a whole-body SAR limit of 0.2–0.4 mW/kg for young children.

==

Related Posts:  

Study: Wireless radiation exposure for children should be hundreds of times lower than federal limits (based on NTP study)

ICNIRP’s Exposure Guidelines for Radio Frequency Fields 

Worldwide Radio Frequency Radiation Exposure Limits versus Health Effects


Wednesday, August 13, 2025

NIEHS Cell Phone Radiation Studies


US Government Releases Report on Pilot Studies of Cell Phone Radiation and DNA Damage


Safety is not assured and questions remain unanswered. 


Electromagnetic Radiation Safety, August 13, 2025


In August 2025, the National Institute of Environmental Health Sciences (NIEHS) published a peer-reviewed report online that described its pilot studies on cell phone radiation exposure conducted by the Division of Translational Toxicology (DTT). These pilot studies were launched specifically “to better understand the biological mechanisms that produced tumor development and DNA damage” as reported in the 2018 rodent studies conducted by the NIEHS National Toxicology Program (NTP).

Although the pilot studies reported “limited findings” and claimed no DNA damage in its 5-day exposure tests, these results cannot be used to conclude that cell phone radiation is safe. Not only were the experiments short-term and limited in scope, but contrary to the stated conclusion of no effects, the authors reported statistically significant evidence of DNA damage. These findings do not negate the findings from the earlier NTP research that reported animals exposed to 14 to 19 weeks of cell phone radiation experienced DNA damage.

The NIEHS's decision to disregard the findings of the DTT and NTP studies, which linked cell phone radiation to DNA damage and cancer, and to halt further research on this environmental carcinogen, represents a failure to uphold its mandate of protecting public health.

The DTT Pilot Studies

The DTT developed a small-scale radio frequency radiation (RFR) exposure system with a signal generator capable of generating a broader array of RF signals than the 2G/3G signals employed in the NTP studies. This system was developed to allow for efficient testing of later generations of cell phone technology (e.g., 4G and 5G).

To help understand the NTP studies, the DTT conducted 2G/3G pilot studies that were limited to 5 days of exposure and used smaller sample sizes compared to the original NTP studies. Nevertheless, these peer-reviewed studies found statistically-significant (p < .05) (in addition to marginally-significant, p < .10) trend effects of cell phone radiation on DNA damage (Wyde et al., 2025):

Male rats: GSM -- hippocampus (p-trend = .002), blood (p-trend = .053), frontal cortex (p-trend = .064)
Female rats: CDMA -- frontal cortex  (p-trend = .043)
Male mice: CDMA --  liver (p-trend = .010), heart (p-trend = .054), blood (p-trend = .077)

Numerous peer-reviewed studies have reported DNA damage caused by cell phone radiation exposure (e.g., Weller et al., 2025Lai, 2021) in addition to the earlier NTP studies. Thus, it is surprising that the DTT report dismissed these adverse effects calling them of "uncertain biological significance."

Overcoming technical challenges, the DTT developed a prototype capable of testing the effects of later generations of cell phone technology. The DTT report concluded:

"Despite a number of difficulties (i.e., engineering requirements, system modifications, measurement of body temperature during exposure), this small-scale RFR exposure system presents a prototype for investigative toxicological studies by researchers interested in conducting experimental RFR studies in rodent models. High-quality studies to understand the effects of RFR exposure on biological responses are needed given the widespread human exposure to RFR associated with cell phone use." 

However, on August 7, 2025, contrary to the results of the DTT report, the NIEHS posted on its website:

 "Also, NIEHS researchers found that exposure to RFR did not induce DNA damage, after five days of continuous exposure, up to 9 watts/kg in rats and 15 watts/kg in mice." https://ntp.niehs.nih.gov/research/topics/cellphones 

And contrary to the report's conclusions, the NIEHS stated:

"The research using this small-scale RFR exposure system was technically challenging and more resource intensive than expected... no further work with this RFR exposure system will be conducted and NIEHS has no further plans to conduct additional RFR exposure studies at this time." https://ntp.niehs.nih.gov/research/topics/cellphones

Results of the NTP Studies

https://www.niehs.nih.gov/sites/default/files/NTP_cell_phone_factsheet_jan_2024_508.pdf

Based on the NTP studies, the NIEHS published a peer-reviewed paper which concluded that exposure to radio frequency radiation (RFR) is associated with an increase in DNA damage (Smith-Roe et al., 2020). The NTP found significant increases in DNA damage in the frontal cortex of male mice (both modulations--GSM and CDMA), leukocytes of female mice (CDMA only), and hippocampus of male rats (CDMA only) from 14-19 weeks of exposure to cell phone radiation. Increases in DNA damage judged to be equivocal were observed in several other tissues of rats and mice. 


Comparison of 2018 NTP Studies and 2025 DTT Pilot Studies 


2018 NTP Studies

2025 DTT Pilot Studies

Purpose

Comprehensive evaluation of cancer and DNA damage risks from long-term cell phone radiofrequency radiation exposure in male and female rats and mice

Mechanistic follow-up to explore possible biological pathways for tumor and DNA damage seen in the 2018 NTP study in male and female rats and male mice

Exposure Duration

14 to 19 weeks for DNA genotoxicity tests


2 years for carcinogenicity study

5 days for DNA genotoxicity tests

Pre-natal Exposure

Yes, for male and female rats, studies began on gestation day 6.

No, for male mice, 5-6 weeks old on first day of study.

No, male rats were 28–31 weeks old, female rats were 23 weeks old, and male mice were 33 weeks old on first day of study.

Cancer 

Increased tumors in male rats:

  • Clear evidence of cancer in the heart (malignant schwannoma)

  • Some evidence of cancer in the brain (malignant glioma)

  • Some evidence of tumors in the adrenal glands (benign, malignant, or complex combined pheochromocytoma)


Did not test for cancer

DNA Damage

Significant increases in DNA damage in:


  • the hippocampus of male rats,

  • the frontal cortex of the brain in male mice, and

  • the blood cells of female mice.


Although report concluded RFR exposure for 5 days did not induce DNA damage, the studies found significant increases in DNA damage in:


  • the hippocampus of male rats,

  • the frontal cortex of the brain in female rats, and

  • the liver in male mice.

 


Related posts:

==

Cell Phone Radiation Follow-up Studies

NIEHS, August 7, 2025

"NIEHS scientists in the Division of Translational Toxicology, which supports the NTP, undertook research to better understand some of the findings seen in the earlier RFR rodent studies reported in NTP Technical reports TR-595 and TR-596.

They designed and developed a novel custom small-scale RFR exposure system, which included building, testing, and validating the exposure system. This new exposure system was based on the system used in the published NTP rodent studies. Researchers then conducted a series of short-term in vivo rodent studies.

NIEHS has completed the follow-up studies with this small-scale RFR exposure system. The results from these follow-up studies are published in a peer-reviewed report posted on the NIEHS website (see sidebar).

The research using this small-scale RFR exposure system was technically challenging and more resource intensive than expected. In addition, this exposure system was designed to study the frequencies and modulations used in 2G and 3G devices, but is not representative of newer technologies such as 4G/4G-LTE, or 5G (which is still not fully defined). Taking these factors into consideration, no further work with this RFR exposure system will be conducted and NIEHS has no further plans to conduct additional RFR exposure studies at this time."

RFR Follow-up Studies

"Following publication of the NTP RFR studies, NIEHS scientists conducted additional research to better understand the biological mechanisms that produced tumor development and DNA damage in exposed rodents. Specifically, they set out to understand if the health effects seen in the original studies were due to direct RFR exposure or RFR-induced changes in the temperature of body-tissue.

The scientists designed and developed a RFR exposure system that employed sub-cutaneous chips and implanted temperature data loggers to measure internal body temperature of rodents. Technical advances of the system also supported improved control of the exposure process and testing of 2G, 3G, 4G-LTE, and unmodulated RF signals. The scientists conducted short-term studies using the new system.

The scientists obtained some limited results. For example, scientists observed no changes in rodent behavior during operation of the RFR exposure system. Also, NIEHS researchers found that exposure to RFR did not induce DNA damage, after five days of continuous exposure, up to 9 watts/kg in rats and 15 watts/kg in mice.

Despite these findings, the new RFR exposure system left the body temperature question unanswered. Neither the microchips nor the data loggers successfully measured internal body temperature of the test rodents making it impossible to draw conclusions about the role of tissue heating in RFR-induced toxicity and carcinogenicity. The system is also incapable of testing many of the frequencies associated with newer 5G cell phone technology. It became clear that this experimental approach is insufficient for additional RFR research by NIEHS.

Nevertheless, the study generated useful exposure information that may support further study by other organizations.

The full, peer-reviewed report of the study is published under the title of Development and Testing of a Novel Whole-Body Exposure System for Investigative Studies of Radiofrequency Radiation in Rodents on the NIEHS website."

https://ntp.niehs.nih.gov/research/topics/cellphones

--

Development and testing of a novel whole-body exposure system for investigative studies of radiofrequency radiation in rodents

Wyde ME, Capstick M, Hall SM, Hooth MJ, Kuster N, Ladbury JM, Roberts GK, Shipkowski KA, Shockley KS, Smith-Roe SL, Stout MD, Walker NJ. 2025. Development and testing of a novel whole-body exposure system for investigative studies of radiofrequency radiation in rodents. Research Triangle Park, NC: National Institute of Environmental Health Sciences. [https://doi.org/10.22427/NIEHS-RFR]

Executive Summary

"The predominant source of human exposure to radiofrequency radiation (RFR) occurs through the use of cell phone handsets. Previous toxicology studies on RFR, conducted in support of the National Toxicology Program (NTP) by researchers at the National Institute of Environmental Health Sciences (NIEHS), found exposure-related effects on body temperature and DNA damage. The studies reported herein were conducted by NIEHS researchers in the Division of Translational Toxicology to better understand the biological mechanisms that produced tumor development and DNA damage in exposed rodents. These studies were not conducted as part of the NTP.

The goals of the current research were to design, construct, and use a small-scale RFR exposure system to conduct toxicological research in rats and mice. One of the primary specific objectives of this research was to test and use new, experimental methods to collect physiological data from animals in real time during RFR exposures, including assessment of body temperature and use of videos for clinical observations. Previously, such data collections were not feasible without cessation of RFR exposure.

A new RFR exposure system based on the technical parameters of the system used in the previous NTP toxicology and carcinogenesis studies was developed for small-scale investigative studies with fewer animals. The system was designed with enhanced capabilities and more flexibility, including the ability to generate additional radiofrequency (RF) signals with frequencies and modulations used in more current wireless communication technologies. After development and installation, the system was rigorously tested and independently verified before animal studies were conducted. Following completion of the mouse study, several system modifications were required before the rat studies could be conducted. These system modifications required significant technical expertise and sometimes took several months to resolve successfully.

A series of 5-day studies was conducted in male or female Sprague Dawley (Hsd:Sprague Dawley® SD®) rats or B6C3F1/N mice to evaluate the effect of exposure to the same Code Division Multiple Access (CDMA)- or Global System for Mobile Communications (GSM)-modulated RF signals used in the previous NTP studies. Video from the cameras in the exposure chambers demonstrated no visible response in either rats or mice at the first time the exposure system was activated, at subsequent system on/off transitions, or during the periods of exposure. Exposure to RFR for 5 days did not induce DNA damage in brain cells (frontal cortex, hippocampus, and cerebellum), or in liver, heart, or blood cells of rats and mice, as measured using the comet assay. These investigative studies of RFR exposure were technically challenging to conduct and, unfortunately, measurement by two different methods did not yield data useful for assessing body temperature during exposure.

Despite a number of difficulties (i.e., engineering requirements, system modifications, measurement of body temperature during exposure), this small-scale RFR exposure system presents a prototype for investigative toxicological studies by researchers interested in conducting experimental RFR studies in rodent models. High-quality studies to understand the effects of RFR exposure on biological responses are needed given the widespread human exposure to RFR associated with cell phone use. The aim of this report is to share knowledge and facilitate advancement in research methodologies for investigating the potential health effects of RFR."

Excerpts

"In the current studies, male rats were exposed to CDMA or GSM-modulated RFR, and female rats and male mice were exposed to CDMA-modulated RFR."

"Based on the homogeneity results of previous analyses that modeled the specific absorption rate (SAR) distribution of RFR across the whole body, rats were exposed at a frequency of 900 MHz, and mice were exposed at 1,900 MHz."

"While reviewing videos captured during exposure (see Section 4.2.3.5), it was noted that the stirrer on the back wall of the control chamber (Chamber 4) did not move throughout the four experiments (male mouse CDMA, male rat CDMA, female rat CDMA, male rat GSM)."

"The signal generator (SMBV-100A, Rhode & Schwarz, Germany) chosen was capable of generating the types of signals used in the previous NTP RFR studies."

"These chambers and the studies described in Section 4.2 utilized a 10-minute on/10-minute off alternating exposure paradigm by which animals in each chamber were exposed for 9 hours and 10 minutes per day over an 18-hour and 20-minute exposure period."

"An RFR field exposure system was designed to enable equivalent exposure conditions to those utilized in the previous NTP 2-year studies and for a smaller number of animals with a smaller facility footprint."

Figure 3: The mouse CDMA study was conducted in July 2020. The rat studies were conducted from September to November 2021.

"During the acclimation period, prior to the start of exposure, it was discovered that the rats were able to chew through the cage filter tops and escape their cage units."

"After system installation, verification, and qualification were completed, a series of four 5-day studies was conducted in Sprague Dawley (Hsd:Sprague Dawley ® SD®) rats or B6C3F1/N mice. The goal of these studies was to further characterize radiofrequency radiation (RFR)-induced changes in body temperature and DNA damage observed in the previous National Toxicology Program (NTP) RFR studies and evaluate the use of new methods for collecting live, real-time data."

"On the first day of the studies, rats were approximately 28–31 weeks (male) or 23 weeks (female) old, and male mice were approximately 33 weeks old. Rats and mice were randomly assigned to one of five exposure groups before the start of the study. Randomization was stratified by body weight that produced similar group mean weights using NTP Provantis software (Instem, Stone, UK)."

"Groups of 10 male and 10 female rats and 10 male mice were housed individually in reverberation chambers and exposed to whole-body RFR via Code Division Multiple Access (CDMA) (Interim Standard 95 [IS-95], 1,900 MHz) or via Global System for Mobile Communications (GSM) single modulation (900 MHz)."

"These studies were conducted under the NIEHS contract with Battelle Memorial Institute (HHSN273201400015C). The studies were initiated at the Battelle testing facility in West Jefferson, Ohio. On May 1, 2021, the testing facility was transferred to a new company, AmplifyBio....For the mouse study, all of the in-life, postmortem, and analytical portions of the study were conducted while Battelle was the testing facility; reporting was conducted under AmplifyBio as the testing facility. The rat studies were conducted under AmplifyBio as the testing facility."

"Body temperature data were unusable because of data quality or data collection issues."

"There were no exposure-related effects on survival or body weights with CDMA-modulated RFR exposure up to 9 W/kg for 5 days in male rats."

"There were no exposure-related effects on body weights with GSM-modulated RFR exposure up to 9 W/kg for 5 days in male rats. On study day 5, body weights showed a negative trend and a significant decrease in the 6 W/kg group compared to the chamber control group."

"Statistical methods were chosen based on distributional assumptions. Unless specifically mentioned, all endpoints were tested for a trend across exposure groups, followed by pairwise tests for each exposed group against the chamber control group. Significance of all trend and pairwise tests is determined by a p value of ≤0.05 and is reported at both 0.05 and 0.01 levels. The room control group was analyzed only by a single pairwise comparison to the chamber control group. The room control analysis was kept separate from that of the other exposed groups and was excluded from all trend tests."

DNA damage from exposure to RFR was assessed in frontal cortex, hippocampus, cerebellum, liver, blood, and heart cell samples from male mice and male and female rats using the comet assay (Table D-1, Table D-2, Table D-3, and Table D-4). For CDMA male mice, there were no significant increases in DNA damage, measured as the percent tail DNA, in cells sampled from the three brain regions, blood, and heart tissue; there was a significant trend test for the percent tail DNA in liver cells that is of uncertain biological significance. For CDMA male and CDMA female rats, no significant increases in the percent tail DNA were observed for any tissue. For GSM male rats, there were no significant increases in DNA damage, measured as the percent tail DNA, in cells sampled from frontal cortex, cerebellum, liver, blood, or heart tissue; there was a significant trend test for the percent tail DNA in hippocampal cells that is of uncertain biological significance.

4.4 Summary: "Five-day studies were conducted in male mice or male or female rats to evaluate the effect of exposure to the same CDMA- or GSM-modulated RF signals used in the previous NTP studies. Video from the cameras in the exposure chambers demonstrated no consistent, exposure-related, and visible changes in activity in either rats or mice the first time the exposure system was activated, at subsequent system on/off transitions, or during the periods of exposure. There were no exposure-related effects on survival or body weights following exposure to RFR for 5 days. There was no increase in DNA damage following exposure to RFR for 5 days, as measured using the comet assay, in brain cells (frontal cortex, hippocampus, and cerebellum), or in liver, heart, or blood cells of mice and rats. Body temperature measurements were collected during the studies using two different devices; however, the data were unusable."

Conclusions

"The studies reported herein were conducted by researchers in the Division of Translational Toxicology (DTT) at the National Institute of Environmental Health Sciences (NIEHS). These studies were not conducted as part of the National Toxicology Program."

"The new small-scale RFR exposure system described in this report was developed by NIEHS/DTT to overcome those limitations with a signal generator capable of generating a broader array of RF signals. In addition to the GSM and CDMA signals at 900 and 1,900 MHz used in the previous NTP studies, the small-scale exposure system could generate signals reflective of more current wireless communications (e.g., Third Generation Partnership Project [3GPP] LTE Frequency Division Duplex [FDD] and Time Division Duplex [TDD], LTE-Advanced, 3GPP FDD/ High-Speed Packet Access [HSPA]/HSPA+, GSM/Enhanced Data rates for GSM Evolution [EDGE]/EDGE Evolution, Time Division-Synchronous CDMA [TD-Whole-body Radiofrequency Radiation SCDMA], Wireless Local-area Network [WLAN]) with frequencies between 9 kHz and 3.2 GHz, modulations with base bandwidths of up to 120 MHz, and carrier frequencies of up to 3,200 MHz."

"In these studies, evaluation of video from the cameras in the exposure chambers demonstrated no consistent, exposure-related, and visible changes in activity in either rats or mice the first time the system was activated, during subsequent system on/off transitions, or during the periods of exposure."

"Equivocal results, showing limited statistically significant effects, were observed for male mouse liver cells (CDMA) and male rat hippocampal cells (GSM) in these 5-day studies. Although it is not possible to directly compare the 5-day and 90-day comet assay studies, it is interesting to note that a positive result for hippocampal cells from male rats exposed to CDMA was observed in the 90-day study."

"High-quality studies to understand the effects of RFR exposure on biological responses are needed given the widespread human exposure to RFR associated with cell phone use."

Excerpts from tables with statistically significant tests of trends for DNA damage




Table D-1. DNA Damage in Male Mice Exposed to Whole-body CDMA-modulated Cell Phone Radiofrequency Radiation for Five Days



Open access report: https://www.niehs.nih.gov/sites/default/files/2025-08/cellphonerfr_long_508.pdf

https://www.niehs.nih.gov/research/atniehs/dtt/assoc/reports/cellphonerfr