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
--
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
--
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
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
--
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
--
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
--
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
--
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
--
