At very high levels, RF waves can heat up body tissues. But the
levels of energy given off by cell phones are much lower, and are not
enough to raise temperatures in the body.
How are people exposed?
The RF waves come from the cell phone's antenna, which is part of
the body of a hand-held phone. The waves are strongest at the antenna
and lose energy quickly as they travel away from the phone. The phone is
often held against the head when a person is on a call. The closer the
antenna is to a user's head, the greater their expected exposure to RF
waves. The body tissues closest to the phone absorb more energy from RF
waves than tissues farther away.
Many factors can affect the amount of energy from RF waves that a person is exposed to, including:
- The amount of time the person is on the phone.
- Whether the person is holding the phone close to the head, or is instead using the speaker mode or a hands-free device. The farther away from a person's body the phone is, the less they are exposed.
- The distance and path to the nearest cell phone tower.
Cell phones adjust their power to use the minimum amount for a good
signal. Being farther away from the tower requires more energy to get a
good signal, as does being inside a building.
- The amount of cell phone traffic in the area at the time. Higher traffic (from many people using cell phones) may require more energy to get a good signal.
- The model of phone being used. Different phones give off different amounts of energy.
Cell phone specific absorption rate (SAR)
The specific absorption rate (SAR) is the amount of RF energy from
the phone absorbed by the user’s body. Different cell phones have
different SAR levels. Cell phone makers are required to report the maximum
SAR level of their product to the US Federal Communications Commission
(FCC). This information can often be found on the manufacturer’s website
or in the user manual for the phone. The upper limit of SAR allowed in
the United States according to FCC safety guidelines is 1.6 watts per
kilogram (W/kg) of body weight.
But according to the FCC, comparing SAR values between phones can
be misleading. The listed SAR value is based only on the phone operating
at its highest power, not on what users would typically be exposed to
with normal phone use. The actual SAR during use varies based on a
number of factors, so it’s possible that a phone with a lower listed SAR
value might sometimes expose a person to more energy from RF waves than
one with a higher listed SAR value.
Do cell phones cause tumors?
Because cell phones usually are held near the head when a person is
on a call, the main concern has been whether the phones might cause or
contribute to tumors in this area, including:
- Malignant (cancerous) brain tumors, such as gliomas
- Non-cancerous tumors of the brain, such as meningiomas
- Non-cancerous tumors of the nerve connecting the brain to the ear (vestibular schwannomas, also known as acoustic neuromas)
- Tumors of the salivary glands
A few studies have also looked at possible links to other types of cancer.
What do studies show?
Researchers use 2 main types of studies to try to determine if something might cause cancer:
- Studies done in the lab (using lab animals or cell cultures)
- Studies looking at groups of people
In most cases neither type of study provides enough evidence on its
own to show if something causes cancer in people, so researchers
usually look at both lab-based and human studies.
The following is a brief summary of some of the major studies that have looked at this issue to date. However, this is not a comprehensive review of all studies that have been done.
Lab studies of RF waves
As noted above, the RF waves given off by cell phones don’t have
enough energy to damage DNA directly or to heat body tissues. Because of
this, it’s not clear how cell phones might be able to cause cancer.
Some studies have found possible increased rates of certain types of
tumors in lab animals exposed to RF radiation, but overall, the results
of these types of studies have not provided clear answers so far.
Large studies published in 2018 by the US National Toxicology
and by the Ramazzini Institute in Italy
exposed groups of lab rats (as well as mice, in the case of the NTP
study) to RF waves over their entire bodies for many hours a day,
starting before birth and continuing for most or all of their natural
lives. Both studies found an increased risk of uncommon heart tumors
called malignant schwannomas in male rats, but not in female rats (nor
in male or female mice, in the NTP study). The NTP study also reported
possible increased risks of certain types of tumors in the brain and in
the adrenal glands.
While both of these studies had strengths, they also had
limitations that make it hard to know how they might apply to humans
being exposed to RF waves from cell phones. A 2019 review of these two
studies by the International Commission on Non-Ionizing Radiation
Protection (ICNIRP) determined that the limitations of the studies
didn’t allow conclusions to be drawn regarding the ability of RF energy
to cause cancer.
Still, the results of these studies do not rule out the possibility
that RF waves from cell phones might somehow impact human health.
Studies in people
Several dozen studies have looked at possible links between cell
phone use and tumors. Most of these studies have focused on brain
tumors. Many of these have been case-control studies, in which patients
with brain tumors (cases) were compared to people who didn't have brain
tumors (controls), in terms of their past cell phone use.
These studies have had mixed results. Some studies have found a
possible link between cell phone use and brain tumors, while others have
not. For example, several studies published by the same research group
in Sweden have reported an increased risk of brain tumors in people
using cell phones.
However, there was no apparent overall increase in brain tumors in
Sweden during the years that correspond to these reports.
Three large studies deserve special mention:
The INTERPHONE study
The 13-country INTERPHONE study, the largest case-control study
done to date, looked at cell phone use among more than 5,000 people who
developed brain tumors (gliomas or meningiomas) and a similar group of
people without tumors. Overall, the study found no link between brain
tumor risk and the frequency of calls, longer call time, or cell phone
use for 10 or more years. There was a suggestion of a possible increased
risk of glioma, and a smaller suggestion of an increased risk of
meningioma, in the 10% of people who used their cell phones the most.
But this finding was hard to interpret because some people in the study
reported implausibly high cell phone use. The researchers noted that the
shortcomings of the study prevented them from drawing any firm
conclusions, and that more research was needed.
Another part of the INTERPHONE study compared more than 1,000
people with acoustic neuromas to more than 2,000 people without tumors,
who served as matched controls. As with gliomas and meningiomas, there
was no overall link between cell phone use and acoustic neuromas. There
was again a suggestion of a possible increased risk in the 10% of people
who used their cell phones the most, but this finding was hard to
interpret because some people reported implausibly high cell phone use.
The Danish cohort study
A large, long-term study
has been comparing all of the people in Denmark who had a cell phone
subscription between 1982 and 1995 (about 400,000 people) to those
without a subscription to look for a possible increase in brain tumors.
The most recent update of the study followed people through 2007. Cell
phone use, even for more than 13 years, was not linked with an increased
risk of brain tumors, salivary gland tumors, or cancer overall, nor was
there a link with any brain tumor subtypes or with tumors in any
location within the brain.
This type of study (following a large group of people going forward
in time and not relying on people’s memories about cell phone use) is
generally thought to provide stronger evidence than a case-control
But this study also has some drawbacks. First, it is based only on
whether or not people had a cell phone subscription at the time. It
didn’t measure how often these people used their phones (if at all), or
if people who didn’t have a subscription used someone else’s phone.
There are also limits as to how well this study might apply to people
using cell phones today. For example, while the cell phones used at the
time of the study tended to emit higher levels of RF waves than modern
cell phones do, people also probably used their phones quite a bit less
than people use their phones today.
The Million Women Study
A large prospective (forward-looking) study of nearly 800,000 women
in the UK
examined the risk of developing brain tumors over a 7-year period in
relation to self-reported cell phone use at the start of the study.
This study found no link between cell phone use and brain tumors overall
or several common brain tumor subtypes, but it did find a possible link
between long-term cell phone use and acoustic neuromas. The authors of
this study, however, did note the possibility that this link might have
been due to more intensive medical investigation in long-term cell phone
users because of media coverage at the time.
All studies done so far have limitations
In summary, studies of people published so far have not established
a clear link between cell phone use and the development of tumors.
However, these studies have had some important limitations that make
them unlikely to end the controversy about whether cell phone use
affects cancer risk.
First, studies have not yet been able to follow people for very
long periods of time. After a known cancer-causing exposure, it often
takes decades for tumors to develop. Because cell phones have been
widely used for only about 20 years in most countries, it is not
possible to rule out possible future health effects.
Second, cell phone usage is constantly changing. People are using
their cell phones much more than they were even 10 years ago, and the
phones themselves are very different from what was used in the past.
This makes it hard to know if the results of studies looking at cell
phone use in years past still apply today.
Third, most of the studies published so far have focused on adults,
rather than children. (One case-control study
looking at children and teens did not find a significant link to
brain tumors, but the small size of the study limited its power to
detect modest risks.) Cell phone use is now widespread even among
younger children. It is possible that if there are health effects, they
might be more pronounced in children because their bodies might be more
sensitive to RF energy. Another concern is that children’s lifetime
exposure to RF waves from cell phones will be greater than adults’, who
started using cell phones when they were older.
Finally, the measurement of cell phone use in most studies has been
crude. Most have been case-control studies, which have relied on
people’s memories about their past cell phone use. In these types of
studies, it can be hard to interpret any possible link between cancer
and an exposure. People with cancer are often thinking about possible
reasons for it, so they may sometimes recall their phone usage
differently from people without cancer.
With these limitations in mind, it is important to continue to
study the possible risk of cell phone exposure, especially with regard
to use by children and longer-term use.
What do expert agencies say?
The American Cancer Society (ACS) does not have any
official position or statement on whether or not radiofrequency (RF)
radiation from cell phones, cell phone towers, or other sources is a
cause of cancer. ACS generally looks to other expert
organizations to determine if something causes cancer (that is, if it is
a carcinogen), including:
- The International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO)
- The US National Toxicology Program (NTP), which
is formed from parts of several different government agencies, including
the National Institutes of Health (NIH), the Centers for Disease
Control and Prevention (CDC), and the Food and Drug Administration (FDA)
Other major organizations also sometimes comment on the ability of certain exposures (such as cell phone use) to cause cancer.
Based on a review of studies published up until 2011, the International Agency for Research on Cancer (IARC)
has classified RF radiation as “possibly carcinogenic to humans,” based
on limited evidence of a possible increase in risk for brain tumors
among cell phone users, and inadequate evidence for other types of
cancer. (For more information on the IARC classification system, see Known and Probable Human Carcinogens.)
More recently, the US Food and Drug Administration (FDA)
issued a technical report based on studies published between 2008 and
2018, as well as national trends in cancer rates. The report concluded:
“Based on the studies that are described in detail in this report, there
is insufficient evidence to support a causal association between
radiofrequency radiation (RFR) exposure and [tumor formation].”
So far, the National Toxicology Program (NTP) has not included RF radiation in its Report on Carcinogens, which lists exposures that are known to be or reasonably anticipated to be human carcinogens. (For more on this report, see Known and Probable Human Carcinogens.)
According to the US Federal Communications Commission (FCC):
“[C]urrently no scientific evidence establishes a causal link
between wireless device use and cancer or other illnesses. Those
evaluating the potential risks of using wireless devices agree that more
and longer-term studies should explore whether there is a better basis
for RF safety standards than is currently used.”
According to the US Centers for Disease Control and Prevention (CDC):
“At this time we do not have the science to link health problems to
cell phone use. Scientific studies are underway to determine whether
cell phone use may cause health effects.”
How can I lower my exposure to RF waves from cell phones?
It is not clear at this time that RF waves from cell phones cause
harmful health effects in people, but studies now being done should give
a clearer picture of the possible health effects in the future. Until
more is known, there are several things that people who are concerned
about RF waves can do to limit their exposure.
Use the speaker mode or video chat feature on the phone, or a hands-free device such as a corded or cordless earpiece.
This moves the antenna away from your head, which decreases the amount
of RF waves that reach the head. Corded earpieces emit virtually no RF
waves (although the phone itself still emits small amounts of RF waves
that can reach parts of the body if close enough, such as on the waist
or in a pocket). Bluetooth® earpieces typically transmit RF waves at much lower power levels than cell phones themselves (see below).
Texting instead of talking on the phone may be another way to reduce your exposure.
But it may not be a good option in some situations, especially if you
are driving. For safety reasons, it is especially important to limit or
avoid the use of cell phones (especially texting) while driving.
Limit your (and your children’s) cell phone use.
This is one of the most obvious ways to limit your exposure to RF waves
from cell phones. For example, you may want to limit the amount of time
you spend talking on the phone (at least with your phone up to your
ear). Parents who are concerned about their children’s exposure can
limit how much time they spend talking on the phone.
Consider choosing a phone with a low SAR value.
Different models of phones can give off different levels of RF waves.
But as noted above, according to the FCC the SAR value is not always a
good indicator of a person’s exposure to RF waves during normal cell
phone use. One way to get information on the SAR level for a specific
phone model is to visit the phone maker’s website. The FCC has links to some of these sites.
If you know the FCC identification (ID) number for your phone model
(which can often be found somewhere on the phone or in the user manual),
you can also go to the following web address: www.fcc.gov/oet/ea/fccid. On this page, you will see instructions for entering the FCC ID number.
Are phones on 5G networks any different?
Fifth generation (5G) cellular networks are now being rolled out in
many parts of the United States and in other countries. 5G networks are
capable of transmitting much larger amounts of data over shorter
periods of time than previous generations (4G, 3G, etc.).
5G networks (and the phones that use them) operate on some higher
frequency (higher energy) RF wavelengths than older generation networks
(although newer phones can typically still use the older networks as
well). But the newer 5G signals still use RF waves, so they are still
forms of non-ionizing radiation, which is not thought to have the ability to directly damage DNA.
The studies that have been done so far to look at possible links
between cell phone use and cancer have focused on older generation
(mainly 2G and 3G) signals. At this time, there has been very little
research showing that the RF waves used in 5G networks are any more (or
less) of a concern than the other RF wavelengths used in cellular
communication. For more on 5G networks, see Cell Phone Towers.
What about cordless phones?
Cordless phones, commonly used in homes, have base units that are
plugged into telephone jacks and wired to a local telephone service.
They are not considered cell phones. Cordless phones operate at about
1/600 the power of cell phones, so they are much less likely to be a
concern in terms of health effects.
What about Bluetooth® devices (including earbuds)?
Many wireless devices now communicate over shorter distances using
Bluetooth technology. For example, many phones now have the option of
using wireless (Bluetooth) earbuds. Phones can also connect to other
devices (tablets, laptops, car dashboard computers, etc.) using
Bluetooth devices use RF waves in a similar wavelength range as
those used for cell phones. But because the signals only need to travel a
short distance (such as from the phone to a person’s ears), they can
operate at much lower power levels than those used by phones, which in
theory might make them less of a health concern. But as with other
devices that give off RF waves, possible health effects from these
devices cannot be ruled out completely at this time.