Updated Cell Phone Study Findings Still Inconclusive

group of people using their cell phones

The US National Toxicology Program (NTP) has released the remaining results of a large study it conducted in rats and mice to try to determine whether the radiofrequency radiation (RFR) used by cell phones might cause cancer. The main findings of the study have not changed since partial results were released in 2016:  It’s still not clear whether RFR, the type of low-energy radiation given off by cell phones while they’re in use, can cause harmful health effects in people.

To conduct the studies, the NTP built special chambers that exposed rats and mice to different levels of RFR. The exposure began while the rodents were still in the womb, and continued for about 2 years, which is all or most of their life. Two years of age for a rat is similar to 70 years of age for a person, according to John Bucher, PhD, NTP senior scientist. The rodents were exposed for about 9 hours a day, and received levels of radiation that ranged from about the upper limit of what is allowed by law for cell phones, to about 4 times higher than what is allowed.

The part of the NTP study released in 2016 suggested that male rats exposed to heavy RFR to their whole body for long periods of time were more likely than a control group of rats to develop certain types of brain tumors (gliomas), as well as a rare type of heart tumor (malignant schwannoma). The NTP focused on these 2 tumor types because some studies in people have also found possible links between cell phone use and these types of tumors. There was no significant difference in tumor rates among the female rats in the study.

The draft of the final report, released today, still noted a significantly higher (although still relatively low) rate of heart schwannomas in the male rats but not female rats. Bucher noted that the gender difference might be due to male rats’ larger size, which led to greater absorption of radiation.

However, there are other findings from these studies that make this finding hard to explain. For example, the newly released results show little indication of an increased risk of tumors or any other health problems in mice exposed to RFR. Also, the male rats exposed to RFR in the study lived, on average, significantly longer than the male rats who were not exposed. The reasons for this are not clear.

The study has not yet been peer reviewed by outside experts, which is typically part of the scientific process before studies are released in their final form. Peer review is expected in March, following a public comment period.

In response to the study’s findings, the US Food and Drug Administration has released a statement saying, “Based on this current information, we believe the current safety limits for cell phones are acceptable for protecting the public health.”

Otis W. Brawley, MD, American Cancer Society Chief Medical Officer, said in a statement, “These draft reports are bound to create a lot of concern, but in fact they won’t change what I tell people: the evidence for an association between cell phones and cancer is weak, and so far, we have not seen a higher cancer risk in people. But if you’re concerned about this animal data, wear an earpiece.”

Should you change your cell phone use?

It’s still not clear whether RFR from cell phones cause harmful health effects in people. The results from this study might not translate directly to cell phone use in people because the animals were exposed over their whole bodies, and were exposed for much longer than people typically use their cell phones, and at higher doses of RFR.

In a conference call with reporters today, Bucher, from the NTP, said he has not changed his own personal cell phone use as a result of the study, nor has he recommended his children make any changes to their cell phone use.

Still, people who are worried about RFR from cell phones can take steps to limit their exposure:

  • Keep the antenna away from your head by using the speaker mode on the phone or a hands-free device such as a corded or cordless earpiece.
  • Text instead of talk. But remember only to text while it’s safe to do so, and never text while driving. According to the Centers for Disease Control and Prevention, any cell phone use can cause distracted driving, which increases the risk of motor vehicle crashes.
  • Limit your (and your children’s) cell phone use. This is one of the most obvious ways to limit your exposure to radiofrequency waves from cell phones. You may want to use your cell phone only for shorter conversations, or use it only when a conventional phone is not available. Parents who are concerned about their children’s exposure can limit how much time they spend on the phone.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.


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