Most studies on cell phone use have not shown increased cancer risk or memory loss. However, two studies show that non-ionizing radiation from cell phones:
• may be associated with impaired ability to recall images, but not spoken words in teenagers (Environmental Health Perspectives, July 2018;126(7):1-13), and
• at high levels, can increase brain and heart tumors in rats (Environ Res, Aug 2018;165:496-503).
Types of Radiation
There are two major types of radiation:
• Ionizing radiation (such as from X rays) that unquestionably can cause cancer and cell damage
• Non-ionizing radiation, from radar, microwave ovens, cell phones and other sources, that has not been linked to cancer but can heat up and damage tissues. Cell phones do not emit the harmful ionizing radiation, but their antennas produce non-ionizing radiation to send messages to distant towers. We do not know if non-ionizing radiation causes significant cell damage, but if there is a possibility, a sensible precaution would be to keep the antenna of the phone away from contact with your head. Nerves are the tissue most susceptible to cell damage from any radiation.
Memory Impairment in Teenagers
Researchers followed 700 Swiss teenagers, ages 12 to 17, for one year and found that higher levels of mobile phone use were associated with lowered ability to recall images, but not spoken words (Environmental Health Perspectives, July, 2018;126(7):1-13). The authors believe that a young developing brain appears to be more susceptible to phone-wave-induced changes up to 15 years of age. They found that the average phone call time for teens was 10.6 minutes per day, and the average cumulative radiation exposure per day was 858 mJ/kg per day. However, most teenagers spend the bulk of their cell phone time using various apps for social media and so forth that do not produce non-ionizing radiation.
Tumors in Rats
In the largest long-term study yet on the health effects of cell phone radiation in rats, 2448 male and female rats were exposed to cell phone radiation from prenatal life until natural death (dose exposure to 1.8 GHz GSM from the antennae of mobile phones for 19 hours a day). Male rats exposed to the highest doses suffered an increased rate of Schwannoma tumors of nerve coverings in their hearts (Environ Res, Aug 2018;165:496-503). These are of the same types of tumors observed in a few epidemiological studies on cell phone users. The authors conclude that, "These experimental studies provide sufficient evidence to call for the re-evaluation of IARC conclusions regarding the carcinogenic potential of RFR [non-ionizing radiation] in humans." (IARC is the International Agency for Research on Cancer.)
Previous Studies on Non-Ionizing Radiation
Non-ionizing radiation does heat up tissue, the way that microwave ovens are used to cook food, but the amount of radiation from cell phones is so low that it does not cause significant heating even if you hold the cell phone antenna close to your body for an extended time. If all of the cell phone radiation was absorbed and went into heating you up, it would take 20,900,000 seconds or 241 days of continuous use to heat you up by one degree (Forbes.com, February 2, 2018).
An older study showed that cell phone radiation caused roundworms to release heat shock proteins that could be a sign of tissue damage (Nature, May 25, 2001). A study from the Swedish National Institute for Working Life found that people who used cell phones for more than an hour a day for 10 years were at increased risk for brain cancers (International Archives of Occupational and Environmental Health, April 2006).
On March 26, 2018, the U.S. National Toxicology Program released its report on Cell Phone Radio-Frequency Radiation, which states that, "High exposure to radio-frequency radiation in rodents resulted in tumors in tissues surrounding nerves in the hearts of male rats, but not female rats or any mice." However, only six percent of the rats were exposed to the highest level of radiation, much higher doses than one gets from cell phones, developed tumors.
It appears that cell phones do not heat up your brain significantly, but as a precaution, I recommend that you keep your phone's antenna more than two inches away from your skin when you are making a call. Use the speaker phone or a blue tooth or wired ear piece. When you sleep, keep the cell phone away from your bed.