Seven-Year Study Finds No Link Between Smartphone Radiation and Brain Tumors

Falling asleep with a smartphone beside the pillow has become routine for many, yet lingering fears about electromagnetic radiation and cancer have persisted.

A large-scale joint study by Korean and Japanese researchers now offers reassurance: seven years of experiments found no clear connection between electromagnetic radiation and cancer development.

The Electronics and Telecommunications Research Institute (ETRI) announced that long-term exposure to radiofrequency (RF) electromagnetic waves from mobile phones showed no statistically significant effect on brain or heart tumor development. The findings were published in Toxicological Sciences, a prestigious international journal.

The research began as an effort to verify a 2018 report by the U.S. National Toxicology Program (NTP) that had shocked the world. The NTP study reported increased tumors in some male rats exposed to electromagnetic radiation, fueling fears about radiation causing cancer. The World Health Organization (WHO) subsequently called for additional verification of whether the results could be replicated and whether the study design was sound.

The Korea-Japan research team launched its fact-checking effort in 2019. Experimental conditions were rigorous: 210 rats were exposed to electromagnetic waves at international human protection standard levels for 24 hours a day over 104 weeks—far exceeding typical human mobile phone usage.

Researchers divided subjects into exposed and control groups, meticulously tracking weight, body temperature, food intake, survival rates, and tumor development. Unlike the U.S. study, no significant differences in cancer rates were found in the brain, heart, adrenal glands, or other major organs. The exposed group actually showed higher survival rates than the control group.

"Previous reports suggesting that electromagnetic exposure at human protection standard levels increases tumors were not replicated in this experiment," said Ahn Young-hwan, a professor at Ajou University School of Medicine who led the research. "This provides scientific grounds to alleviate vague fears about electromagnetic radiation."

The International Agency for Research on Cancer (IARC) currently classifies mobile phone electromagnetic waves as "possibly carcinogenic" (Group 2B)—the same category as pickled vegetables like kimchi. The new findings are expected to serve as key reference material when the IARC reassesses its carcinogenicity classification.

The researchers cautioned that the results do not guarantee 100% safety across all frequency bands. Since experiments were based on existing communication networks, additional research on new technologies such as 5G remains necessary.

Separately from cancer risk, experts note that strong blue light from smartphone screens suppresses melatonin, the sleep-inducing hormone. While mobile phone use within current protection standards shows no confirmed direct link to cancer, experts advise keeping phones away from the bedside during sleep to reduce blue light exposure and sleep disruption.