Article publication date
January 2026
ARPANSA review date
25 February 2026
Summary
These two large studies, simultaneously but independently conducted in Korea (Kim et al., 2026) and Japan (Imaida et al., 2026), investigated whether long‑term exposure to radiofrequency electromagnetic fields (RF-EMF) can cause tumours or genetic damage in rats. These studies were particularly designed to substantiate earlier findings from the U.S. National Toxicology Program’s (NTP) study, which had reported increased rates of rare tumours, particularly brain gliomas and heart schwannomas, in male rats exposed to RF-EMF at very high exposures (given as the specific absorption rate (SAR)). To test whether these results could be reproduced and validated, both countries used the same protocol, rat strain, exposure system and RF-EMF signal (900 MHz, CDMA) at a whole‑body SAR level of 4 W/kg. Both studies followed strict Good Laboratory Practice and OECD guidelines (e.g., TG451). Exposure began before birth and continued for two years, with rats receiving RF-EMF exposure for 18 hours and 20 minutes per day in 10 minute on/off cycles. The study included three groups of rats of 70 animals each, one group being those exposed to RF-EMF, one sham exposed and one group of cage controls. The incidence of tumours was assessed by histopathology which underwent international peer review.
The findings of these studies were remarkably consistent and in contrast to the NTP study as there were no statistically significant changes in tumour incidence in either study. In the Japanese study, the RF-EMF exposed group lived longer than the sham exposed group, although still within normal variation. This was attributed to slightly lower food consumption and weight in the exposed group and was accounted for statistically. Similarly, the studies reported no evidence of DNA damage or chromosomal aberrations in exposed rats. The results of this Japan–Korea collaborative research do not substantiate the results previously reported by the NTP study.
Published in
Toxicological Sciences
Link to study
Link to Korean and Japanese studies
Commentary by ARPANSA
These two studies are among the largest to investigate tumour outcomes in rats exposed to RF‑EMF, with each including 210 animals. Both studies followed a high standard of methodological rigour, including adequate blinding during exposure and analysis, good exposure characterisation and appropriate statistical methods. Together, these features minimise the potential for bias and position these two studies to have a significant influence on the over-arching scientific literature in this domain and any future meta-analyses. The concerted effort by an international research collaboration to simultaneously and independently conduct two large, long-term animal studies is also commendable and highlights the importance of these results.
These partial replication studies used a single exposure level of 4 W/kg, compared to the original NTP study that had groups of animals that were exposed at either 1.5 W/kg, 3 W/kg or 6 W/kg. The maximum exposure level of 6 W/kg has been the subject of criticism by the International Commission on Non-Ionizing Radiation Protection (ICNIRP), the German federal office for radiation protection (BfS) and ARPANSA. These criticisms argue that a core temperature rise at this exposure magnitude would exceed 1°C and the methodology used to evaluate body temperature in the NTP pilot study likely underestimated temperature rise. Where the NTP pilot study measured subcutaneous temperature only after exposure ended, contemporary core temperature monitoring studies have used superior surgically implanted monitors that continuously record core temperature throughout exposure (Bala et al., 2025). The rationale for using high doses is that such doses enhance the experiment’s sensitivity to small or rare outcomes (Haseman & Lockhart, 1994). Without careful control, this can risk tumours occurring secondary to other harms caused by exposure (Bucher, 2000). That adds to the challenge of interpreting the results in relation to humans as the cause of any observed effect becomes unclear. It is therefore justified for the Japanese and Korean replications to use 4 W/kg. This is also the putative level for health effects that the whole body SAR restriction is conservatively based off in the ICNIRP guidelines (2020) and the Australian radiofrequency standard RPS-S1 (2021).
Neither the Korean or Japanese study reported an increased incidence of tumours. These findings align with a recent systematic review and meta-analysis by Pinto et al., (2023), which concluded that evidence for any association between RF‑EMF exposure and tumour development is low or inadequate. In contrast, a systematic review and narrative synthesis by Mevissen et al., (2025) reported high‑certainty evidence for an increased incidence of brain tumours (gliomas) and heart tumours (malignant schwannomas) following RF‑EMF exposure, along with moderate evidence for several other tumour types in rats. ARPANSA has previously provided commentary on this review as well as other national health bodies (BfS, Swedish Radiation Safety Authority).
The differing conclusions between these reviews originates from their approaches to evaluating the evidence. Mevissen et al. placed substantial weight on the outcomes of two chronic cancer bioassays, particularly the National Toxicology Program (NTP) rat study (NTP, 2018), without fully accounting for its limitations or integrating the findings of other relevant studies. The authors of the Mevissen review justify this methodology by stating that the available research was not similar enough to enable an encompassing synthesis of the evidence. Although the validity of this justification is poor, such reasoning can never be applied to these two new chronic cancer bioassays from Japan and Korea. As such, even if the critically flawed methodology of the Mevissen et al. review were followed, the conclusions would have to yield to accommodate the findings of this new research. Similarly, the findings reported by Pinto et al. would be further strengthened as the data offered by the two new studies is in alignment with their conclusions. The genotoxicity results are also consistent with a recent systematic review (Romeo et al., 2024) and the results likewise strengthen those conclusions.
Another important issue that should be considered when interpreting these and the results of the NTP studies is the proportion of rats that survived to the end of the experiment. Longer survival rates increase the likelihood of tumour development. In the NTP study, survival among exposed male rats was substantially higher (50–62%) than in the control group (28%). A similar pattern was observed in the Japanese study, although the difference was less pronounced, with 65% survival in exposed rats compared with 43% in sham controls. In contrast, the Korean study reported no meaningful difference in survival rates between exposed and control animals. When exposed animals live significantly longer than controls, as seen in the NTP and Japanese studies, any increase in tumour detection may simply reflect extended lifespan rather than an effect of RF‑EMF. The Japanese study accounted for these differences in mortality through their statistical methods.
For some health endpoints, there is limited relevance of rat cancer studies for extrapolation to human cancer risk. Notably for glioma, some of the molecular features seen in human glioma are not seen in rat glioma, indicating a fundamental biological difference (Sahu et al., 2022). These types of fundamental differences between human and animal biology speak to the importance of the hierarchy of scientific evidence where the most significant evidence comes from studies on humans. This is because studies on humans can provide more direct and relevant information about human health and disease. Human evidence of the association between RF-EMF on cancer has recently been reviewed in the WHO commissioned systematic reviews looking at observational studies in humans (Karipidis et al., 2024, Karipidis et al., 2025). These studies did not find an association between RF-EMF and any cancer type, including glioma.
Although the OECD Test Guideline 116 recommends approximately 50 rats per group, and these studies used 70 animals per group, such numbers may still be insufficient to reliably detect rare cancers. This is particularly relevant given that the background incidence of glioma in NTP control groups is typically only 0–4% (NTP, 2025), meaning that these may still have limited power to identify small increases in rare cancers like glioma.
In Australia, devices that emit RF-EMF must comply with the limits prescribed in the radiofrequency standard RPS-S1. It is important to note that under this standard, the maximum permissible whole body SAR for the general public is 0.08 W/kg, one fiftieth of the exposure level used in these animal carcinogenesis studies. Overall, these new animal studies provide further evidence that RF-EMF is not associated with cancer in animals, supporting previous safety assessments (ICNIRP, 2020; SCHEER, 2022). It is similarly supportive of ARPANSA’s assessment that there is no substantiated scientific evidence of adverse health effects from RF-EMF exposure at levels below those prescribed in the standard.
