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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

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Authors not listed · 2026

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Korean rat study found no cancer or genetic damage from lifelong CDMA 900 MHz exposure at safety guideline levels.

Plain English Summary

Summary written for general audiences

Korean researchers exposed male rats to CDMA-modulated 900 MHz radiofrequency radiation at 4 W/kg (the international safety guideline level) for nearly their entire lifespans. They found no increased cancer rates, no genetic damage, and no effects on heart, brain, or adrenal glands. This was part of a coordinated study with Japan to verify earlier National Toxicology Program findings.

Why This Matters

This study represents a significant attempt to replicate and verify the controversial National Toxicology Program findings that showed increased cancer rates in rats exposed to cell phone radiation. The Korean results directly contradict the NTP's conclusions, finding no carcinogenic effects at the same 4 W/kg exposure level that corresponds to international safety guidelines. What makes this particularly noteworthy is the rigorous methodology - the researchers used the same protocol as their Japanese counterparts and conducted partially blinded evaluations to minimize bias.

However, the study's focus on CDMA-modulated 900 MHz signals reflects older technology, while today's smartphones primarily use different modulation schemes and frequencies. The 4 W/kg exposure level, while matching safety guidelines, is also significantly higher than typical real-world exposures from phones held at normal distances. The conflicting results between this study and the NTP highlight the ongoing scientific uncertainty around RF radiation's long-term health effects.

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 900 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 900 MHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study.

Cite This Study
Unknown (2026). 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.
Show BibTeX
@article{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_ce4725,
  author = {Unknown},
  title = {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},
  year = {2026},
  doi = {10.1093/toxsci/kfag001},
  
}
DOI: 10.1093/toxsci/kfag001PubMed: 41546387

Quick Questions About This Study

CDMA (Code Division Multiple Access) was a digital cellular technology popular in the 2000s. The 900 MHz frequency was commonly used for 2G and early 3G networks, though most modern phones now use different technologies and frequencies.
4 W/kg represents the international safety limit for whole-body exposure. Typical cell phone use results in much lower exposures, usually under 2 W/kg and only to localized areas near the phone, not the whole body.
The Korean study found no cancer increase while the NTP study did. Possible explanations include different rat strains, facility conditions, or statistical analysis methods. This highlights ongoing scientific uncertainty about RF radiation health effects.
Starting RF exposure during fetal development tests the most sensitive life stage. The fact that no effects were found even with this early, prolonged exposure strengthens the study's negative findings regarding carcinogenic potential.
Partially blinded means pathologists examining tissue samples didn't know which exposure group each sample came from, reducing bias. This methodological approach strengthens confidence in the findings that no RF-related tissue changes occurred.