Do Cell Phones Cause Cancer?

An illustration of a man holding a cell phone

Cell phones emit low-energy radiation in the form of radiofrequency waves. Scientists are investigating whether these waves post a cancer risk.

Back in 1993, a Florida resident named David Reynard went on CNN’s Larry King Live to warn about the dangers of cell phone radiation. He said it caused his wife’s brain tumor. Ever since, the question of whether cell phones cause cancer has buzzed quietly in the background as the technology has become omnipresent in our lives.

Numerous studies of cell phone radiation and cancer have been conducted over the years to address the issue, but none has been definitive.

To obtain more solid evidence, a team of scientists at the National Toxicology Program, a division of the National Institutes of Health, undertook an in-depth study. Their approach was to expose laboratory rodents to high doses of cell phone radiation over their entire life span and see if they developed cancer as a result. The study cost $20 million and took more than ten years to complete. Final results were released to the public in November 2018.

The argument that cell phones cause cancer lacks biological plausibility because the energy contained in the waves is too low to cause damage.

To the surprise and alarm of many, the investigators found what they called “clear evidence” that cell phone radiation could cause a type of nerve tissue cancer called a malignant schwannoma in rats. They also reported finding what they said was “some evidence” in the animal studies that cell phone radiation could cause a brain cancer called glioma.

These results generated some scary-sounding news headlines. But according to Lawrence Dauer, a radiation expert at MSK, there’s no reason to freak out just yet.

“The bottom line is it’s a really cool study,” Dr. Dauer says. “But we have to recognize the limitations that come along with it.”

Those limitations fall into three main categories, he says: statistical challenges, extrapolating lessons from rodents to humans, and questions about dosing.

Small Numbers, Big Inconsistencies

In their study, the National Toxicology Program investigators zapped more than 1,200 rats and mice with cell phone radiation — equivalent to that emitted by 2G and 3G phones — over their entire body for nine hours a day for two years. (The amounts given were more than are permitted for humans by the Federal Communications Commission.) They then looked in different tissues for signs of cancer.

They found that 6% of the male rats exposed to the highest dose of cell phone radiation developed malignant schwannomas in the heart, while 2 to 3% developed gliomas in the brain. None of the control rats (which did not receive radiation) developed either cancer.

These cancers are generally rare in humans, and also deadly, so if cell phone radiation increases their incidence, it is something to worry about indeed. However, there are reasons to doubt these numbers, Dr. Dauer explains. The total number of rats in each treatment group was 90. Six percent of 90 is five rats. Three percent is two rats. When sample sizes are small, simple chance can play a large role in the outcomes.

Say the word 'radiation' and depending on your generation, you're thinking either Teenage Mutant Ninja Turtles or the atomic bomb.
Lawrence T. Dauer clinical physicist

Making this result more difficult to interpret is that, for unknown reasons, the control rats did not live as long as the experimental rats. Because cancer affects animals more as they age, it’s possible that the control rats simply didn’t live long enough to develop tumors. (In past studies, some of the control animals have developed these types of tumors.)

A further curiosity about the study was that only male rats seemed to be affected. The female rats, female mice, and male mice were not affected.

“All told, these features of the study make it difficult to judge whether the cancer effect was real,” he says.

Back to top

Rats Are Not Humans

Even if the results had been more consistent, it would still be difficult to know what they mean for human health. Though rodents are useful tools for learning about basic biology, they don’t necessarily indicate how humans will respond. Since the radiation was more intense and given over the whole body, it is hard to extrapolate the danger to human health. The radiation was also representative of an older form of cell phone technology, 2G and 3G. Fourth generation (4G) phones are in use now and 5G ones are about to be released.   

When making safety recommendations, public health officials typically place more weight on evidence from human studies or trials. In the case of cell phones, several large human studies have been conducted to analyze the potential link between cell phone use and brain cancer. Typically, these are studies in which individuals with brain tumors are surveyed about their cell phone use and compared with individuals without brain tumors. Overall, these studies do not show a link between cell phone use and cancer.

“Any individual study might find something unusual,” Dr. Dauer says. “But what’s most important to consider is the weight of evidence across all of them.” And that, he says, does not show any clear link between cell phones and cancer.

Nor do the available data on cancer incidence show that rates of brain cancer are increasing.

“A questioning scientist might say, ‘Well, we just haven’t used them long enough to see an effect on cancer rates.’ That’s why it’s important to continue to study this,” he adds.

An ongoing study called COSMOS that is being conducted in several European countries is following cell phone users for 20 to 30 years.

When Is a Headache a Symptom of a Brain Tumor?
Find out when to consult a doctor for a bad headache.
Back to top

Not All Radiation Is the Same

When trying to convey an accurate assessment of radiation risk, public health officials run into problems because of confusion over the term.

“Say the word ‘radiation’ and depending on your generation, you’re thinking either Teenage Mutant Ninja Turtles or the atomic bomb,” Dr. Dauer says. “You can’t see it, taste it, smell it, or touch it, and you feel like you can’t do anything about it. So it becomes something very scary.”

But cell phone radiation is actually very low in energy. On the spectrum of electromagnetic radiation, which also includes visible light, cell phone radiation falls between FM radio waves and microwaves. These low-frequency forms of energy are referred to as nonionizing radiation because they are not strong enough to knock atoms off molecules. This is in contrast to ionizing radiation, such as X-rays and gamma rays. These high-frequency waves can indeed damage molecules and have been linked to cancer. (The former are emitted by X-ray machines, while the latter are emitted by radioactive materials.)

The argument that cell phones cause cancer lacks biological plausibility because the energy contained in the waves is too low to cause damage. “There’s no mechanism that we can come up with yet,” Dr. Dauer says. “That doesn’t mean that there might not be one, but it could be so mild or insignificant that it doesn’t show up in an epidemiological study.”

So what’s the take home for average users who want to protect themselves from what may not even be a real danger?

“Use an earpiece or speakerphone if you want,” Dr. Dauer says. “But there are far more concrete dangers of cell phones to worry about, such as texting while driving.”


Addendum added May 21, 2019:

Several readers of this blog post have asked questions about the safety of 5G technology. The study under discussion evaluated radiofrequency radiation from 2G and 3G phones and therefore cannot be extrapolated to 4G or 5G models. But here is what we can say:

Cell phones (and other radiofrequency-emitting devices) are characterized by the frequency of the radiation they use. Early models (2G and 3G) used radiofrequencies in the range of 800 megahertz (MHz) to 1.9 gigahertz (GHz). The 4G range is 700 MHz to 27 GHz. The 5G range will be 600 MHz to 39 GHz. Radiofrequencies in the higher range are actually less able to penetrate the body than lower radiofrequencies, so the risk of these waves doing damage to internal organs is also lower. The frequencies the human body absorbs most efficiently are in the range of 30 to 300 MHz.

While radiofrequency radiation cannot ionize molecules, it can heat them. This is how microwave ovens work. But to heat molecules, the radiation must be given at very high power, on the order of thousands of watts per kilogram (kg). Current safety standards limit cell phones to a maximum of 1.6 watts per kg, which is not enough to warm the body. This safety limit applies to 5G cell phones as well. 

In the study discussed in this post, the power ranged from 1.5 to 6 watts per kg of body weight in rats and 2.5 to 10 watts per kg in mice — thus, in most cases, much higher than the maximum allowed power for humans.

When your phone gets hot, it’s because of the battery, not the radiofrequency.

Additional information can be found here:

Back to top


Commenting is disabled for this blog post.

I suggest you to write about influence of cellphone towers irradiation on human health. It is something to be really worried about.

Another thing to add to the severe shortcomings already mentioned. Did the study look for other types of cancer besides these two? Or did it cherrypick the two where control sample did better? It's a shame that we pay so much attention to pseudo science.
As for the comment about cell towers, the writer seems to be equating intensity of the radiation (as in how many photons per unit time) with the energy of the radiation (as in the energy of each photon). This article has explained that the latter is too low to be ionizing to cause damage. Cell tower does not change this point.

This extensive study did indeed show an increase in cancer in rats exposed to cell phone radiation. Full stop. Rather than dismissing the results, MLK should inform us what was planned to be further research should the study show increase in cancer.

1) Are there simultaneous tests in process for 4g and 5g. I would hope so.
2) Wouldn't we see a rise in the rate of schwannomas and gliomas in human population over the last 10 years? Has it happened.
3) Wouldn't you re-create a larger control group in order to get a non-dosed group of the same life span as the dosed group and then compare cancer rates?

4) If one took on face value that there is a relationship, then wouldn't there be a study with lower dosing to determine a safe level?

I agree with Anna. A great study group to bring in would be mobile carrier tower service workers. Obviously, I see some non-disclosure issues that could arise but the towers and associated companies that use/lease for use could remain anon. In my mind, this would be the demographic most at risk.

wait till we start getting pumped full of the 29Ghz radiation from 5G. Non-stop, cell towers on each block. The human microwave

Cell phones also use 2.4ghz microwaves for wifi, which has a very clear mechanism of energizing water molecules. What about the amount of energy from this antenna pressed directly against the body a lot of the day?

Adam and Anna: The electromagnetic spectrum is the same for cellphones at the phone and the tower. They are both non-ionizing. Because of the power involved at the source, you obvious wouldn't want to stand right next to the broadcast vanes, but those towers are high in the air, and are subject, like all electromagnetic waves to the inverse square law. By the time an isotropic (non-beam forming source) signal is only a few feet from the antennae, it is already quite diffuse. On the ground, even near the source, the exposure is negligible. Cell phone radios (that is what these are) need only a very weak signal to transmit data.
If you are concerned about cell phones, you should be just as concerned about wifi routers and baby monitors, since they transmit on frequencies near 4G cell phones.

OK, I won't give cell phones to rats!

Robert's comment is excellent, but I think a clearer explanation would help non-technical folks.

Anna and Adam (and many others) are confusing the energy associated with the output power (how strong the signal is) and the energy associated with the frequency. The higher the frequency of radiation, the more energy it contains. Only the frequency-related energy can change your DNA and cause cancer.

If you stand next to the antenna on a cell phone tower, the transmitted energy might cook you like a hot dog. It won't change your DNA, because the frequency is too low.

Here's a Wikipedia link about ionizing radiation:

Notice the frequency chart at the right. Cell phone energy is between FM radio and microwaves, too low in frequency to alter DNA. Later on that page is an explanation of molecularly damaging radiation, which starts at the top end of visible light. So, the UV in sunlight (that causes sunburn) can give you cancer, but cell phone radiation will only heat you up.

Interesting that the study was done on 2G and 3G but as the author states, 4G is in use and 5G is on the way. Why not mention the associated power levels compared to the study, more or less. Information deficit and editorially weak.

Also noted questions about the sample size being small which causes the reader to doubt the results. Doesn't the control group account for this? Statistics and t test comparisons could define this perceived ambiguity. Editorially weak

Thanks for the comment, Robert. This is an argument I bring up any time I'm around folks concerned about being in proximity to towers. As far as the workers go, the dangers of working near high powered RF sources are well documented, but even though we take plenty of cautions around dish and sector antennas the amount of energy hitting us while we're up there is still on the low end due to the design of directional antennas. The most dangerous sources of RF we come across are typically from omni-directional antennas used for broadcasts and communications at much lower frequencies, and those are typically coordinated to have their transmitters disabled or to operate at reduced power during work on a tower.

What Robert said. The photons in visible light are more energetic than microwave photons. Therefore, if cell phones or towers pose a risk, then flashlights would be more dangerous.

You published an error in the following sentence. "To the surprise and alarm of many, the investigators found what they called “clear evidence” that cell phone radiation could cause a type of nerve tissue cancer called a schwannoma in rats." If you click on the link to "schwannoma," on your own website, you'll see that vestibular schwannoma isn't cancerous at all.

Thank you for your comment, Jennifer. While most schwannomas are benign, some are malignant. The ones observed in the rats were malignant. We have clarified the sentence. Thank you. 

If I read this correctly, this "in-depth" study only included radiation types found in older technology 2G and 3G phones. I would encourage you to address the more prevalent 4G and soon to be rolled out 5G bandwidths in your study before concluding cell phone radiation as something that "may not even be a real danger".

Additionally, anyone that would be climbing a tower to service a cell site or any other radio broadcast equipment is required by law to be properly trained in the hazards associated with being near a radio transmitter.

Much of this is dependent upon exposure time limits, amongst other things. Much the same as you can't get a sunburn if you limit your time in direct sun, you can't be harmed by the types of radiation present at most sites if you keep proper distances and remove yourself outside the field at certain intervals.

The FCC's regulations on this are very strict and if someone was to try and make their employees work around the regulations, the fines involved would be significant.

Robert: You mention the inverse square law or intensity of the radiation, but another important factor that determines how the human body is affected by radiation, is duration. Yes, cell phone radiation is lower level than X-ray machines emit, but the duration of cell phone radiation exposure is near constant. Even our exposure to sunlight is typically of a much less duration than we are exposed to cell phones and similar radiation sources (yes, wifi routers) in the home. The number of these radiation sources are ever increasing. I wouldn't discount the effects just yet.

Very informative.

This is quite useful for me