Health risks from cell phones and cell phone towers

Safety of cell phones and cell phone towers

With cell phones being used every day in Canada, questions have been raised about their safety. Some members of the public have also expressed concern about the possible health effects of living near cell phone towers.

Cell phones and cell phone towers

The radiofrequency fields given off by cell phones and cell phone towers is a type of non-ionizing radiation. It is similar to the type of energy used in AM/FM radio and TV broadcast signals. Unlike ionizing radiation (as emitted by X-ray machines), RF energy from cell phones and other wireless devices cannot break chemical bonds in your body.

Cell phones and cell phone towers in Canada must meet regulatory requirements that limit human exposure to RF energy. See the section “The Government of Canada’s Role” for further details. Cell phones emit low-levels of radiofrequency (RF) energy, some of which is absorbed into your body. The amount of RF energy you absorb depends on many factors, such as how close you hold the cell phone to your body and the strength of the signal.

Cell phones are designed to operate at the minimum power necessary to connect and maintain a quality call. Cell phones send and receive radio signals from a network of fixed, low-power, cell phone towers (or base stations). These towers are usually located on rooftops, towers and utility poles. The transmitting power of a cell phone varies, depending on the type of network and its distance from the cell phone tower. The power generally increases the further you move away from the nearest cell phone tower.

Health risks from cell phones and cell phone towers

The number of cell phone users in Canada rose from 100,000 in 1987 to more than 24 million by the end of 2010. To meet the demand for new wireless services, cell phone towers have been put up across the country.

There are a small number of epidemiology studies that have shown brain cancer rates may be elevated in long-term/heavy cell phone users. Other epidemiology studies on cell phone users, laboratory studies and animal cancer studies have not supported this association.

In 2011, the International Agency for Research on Cancer (IARC) classified RF energy as “possibly carcinogenic to humans”. The IARC classification of RF energy reflects the fact that some limited evidence exists that RF energy might be a risk factor for cancer. However, the vast majority of scientific research to date does not support a link between RF energy exposure and human cancers. At present, the evidence of a possible link between RF energy exposure and cancer risk is far from conclusive and more research is needed to clarify this “possible” link. Health Canada is in agreement with both the World Health Organization and IARC that additional research in this area is warranted.

Although the RF energy from cell phones poses no confirmed health risks, cell phone use is not entirely risk-free. Studies have shown that:

  • Using cell phones or other wireless devices can be distracting. Your risk of serious injury may increase if you use these devices while driving, walking, cycling, or doing any other activity that requires concentration for personal safety.
  • Cell phones may interfere with medical devices such as cardiac pacemakers, defibrillators, and hearing aids.
  • Cell phones may also interfere with other sensitive electronic equipment, such as aircraft communication and navigation systems.

With respect to cell phone towers, as long as exposures respect the limits set in Health Canada’s guidelines, there is no scientific reason to consider cell phone towers dangerous to the public.

Reduce your risk

Health Canada reminds cell phone users that they can take practical measures to reduce their RF exposure by:

  • limiting the length of cell phone calls
  • using “hands-free” devices
  • replacing cell phone calls with text messages

Health Canada also encourages parents to take these measures to reduce their children’s RF exposure from cell phones since children are typically more sensitive to a variety of environmental agents.

Precautions to limit exposure to RF energy from cell phone towers are unnecessary because exposure levels are typically well below those specified in health-based exposure standards.

The Government of Canada’s Role

Health Canada has developed guidelines for safe human exposure to RF energy. The current version of these exposure guidelines is specified in a document called: Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range from 3 kHz to 300 GHz – Safety Code 6 (2015).

The limits specified in these guidelines are based on an ongoing review of published scientific studies on the health impacts of RF energy. Using data from these studies, Health Canada set the general public exposure limits 50 times lower than the threshold for potentially adverse health effects.

Cell phones are regulated by Industry Canada. This department also oversees the licensing and placement of cell phone towers, considers the effects on the environment and local land use before towers are installed, and ensures that these towers comply with regulatory requirements. Industry Canada has adopted part of Health Canada’s RF exposure guidelines to protect the general public by ensuring that exposure from cell phones and cell phone towers do not exceed the specified limits.

Health Canada continues to monitor the science regarding RF exposure and would take action if future research establishes that RF energy exposure poses a health risk to Canadians.

Cellular Phone Towers

Cellular (cell) phones first became widely available in the United States in the 1990s, but since then their use has increased dramatically. The widespread use of cell phones has led to cell phone towers being placed in many communities. These towers, also called base stations, have electronic equipment and antennas that receive and transmit radiofrequency (RF) signals.

How do cellular phone towers work?

Cell phone base stations may be free-standing towers or mounted on existing structures, such as trees, water tanks, or tall buildings. The antennas need to be high enough to adequately cover the area. Base stations are usually from 50-200 feet high.

Cell phones communicate with nearby cell towers mainly through radiofrequency (RF) waves, a form of energy in the electromagnetic spectrum between FM radio waves and microwaves. Like FM radio waves, microwaves, visible light, and heat, they are forms of non-ionizing radiation. This means they do not directly damage the DNA inside cells, which is how stronger (ionizing) types of radiation such as x-rays, gamma rays, and ultraviolet (UV) light are thought to be able to cause cancer.

At very high levels, RF waves can heat up body tissues. (This is the basis for how microwave ovens work.) But the levels of energy used by cell phones and towers are much lower.

When a person makes a cell phone call, a signal is sent from the phone’s antenna to the nearest base station antenna. The base station responds to this signal by assigning it an available radiofrequency channel. RF waves transfer the voice information to the base station. The voice signals are then sent to a switching center, which transfers the call to its destination. Voice signals are then relayed back and forth during the call.

How are people exposed to the energy from cellular phone towers?

As people use cell phones to make calls, signals are transmitted back and forth to the base station. The RF waves produced at the base station are given off into the environment, where people can be exposed to them.

The energy from a cellular phone tower antenna, like that of other telecommunication antennas, is directed toward the horizon (parallel to the ground), with some downward scatter. Base station antennas use higher power levels than other types of land-mobile antennas, but much lower levels than those from radio and television broadcast stations. The amount of energy decreases rapidly as the distance from the antenna increases. As a result, the level of exposure to radio waves at ground level is very low compared to the level close to the antenna.

Public exposure to radio waves from cell phone tower antennas is slight for several reasons. The power levels are relatively low, the antennas are mounted high above ground level, and the signals are transmitted intermittently, rather than constantly.

At ground level near typical cellular base stations, the amount of RF energy is thousands of times less than the limits for safe exposure set by the US Federal Communication Commission (FCC) and other regulatory authorities. It is very unlikely that a person could be exposed to RF levels in excess of these limits just by being near a cell phone tower.

When a cellular antenna is mounted on a roof, it is possible that a person on the roof could be exposed to RF levels greater than those typically encountered on the ground. But even then, exposure levels approaching or exceeding the FCC safety guidelines are only likely to be found very close to and directly in front of the antennas. If this is the case, access to these areas should be limited.

The level of RF energy inside buildings where a base station is mounted is typically much lower than the level outside, depending on the construction materials of the building. Wood or cement block reduces the exposure level of RF radiation by a factor of about 10. The energy level behind an antenna is hundreds to thousands of times lower than in front. Therefore, if an antenna is mounted on the side of a building, the exposure level in the room directly behind the wall is typically well below the recommended exposure limits.

Do cellular phone towers cause cancer?

Some people have expressed concern that living, working, or going to school near a cell phone tower might increase the risk of cancer or other health problems. At this time, there is very little evidence to support this idea. In theory, there are some important points that would argue against cellular phone towers being able to cause cancer.

First, the energy level of radiofrequency (RF) waves is relatively low, especially when compared with the types of radiation that are known to increase cancer risk, such as gamma rays, x-rays, and ultraviolet (UV) light. The energy of RF waves given off by cell phone towers is not enough to break chemical bonds in DNA molecules, which is how these stronger forms of radiation may lead to cancer.

A second issue has to do with wavelength. RF waves have long wavelengths, which can only be concentrated to about an inch or two in size. This makes it unlikely that the energy from RF waves could be concentrated enough to affect individual cells in the body.

Third, even if RF waves were somehow able to affect cells in the body at higher doses, the level of RF waves present at ground level is very low – well below the recommended limits. Levels of energy from RF waves near cell phone towers are not significantly different from the background levels of RF radiation in urban areas from other sources, such as radio and television broadcast stations.

Studies in people

Very few human studies have focused specifically on cellular phone towers and cancer risk.

In one large study, British researchers compared a group of more than 1,000 families of young children with cancer against a similar group of families of children without cancer. They found no link between a mother’s exposure to the towers during pregnancy (based on the distance from the home to the nearest tower and on the amount of energy given off by nearby towers) and the risk of early childhood cancer.

In another study, researchers compared a group of more than 2,600 children with cancer to a group of similar children without cancer. They found that those who lived in a town that could have exposed them to higher than average RF radiation from cellular phone towers in the previous 5 years had a slightly higher risk of cancer, although not of any certain type of cancer (like leukemia or brain tumors). This study estimated the children’s possible exposure based on the number of towers in their town and how strong the signals were from the towers. It did not look at actual exposure of any individual child based on how far their home or school was from a tower. This limitation reduces confidence in the results of the study.

One study looked for signs of DNA and cell damage in blood cells as a possible indicator of cancer-causing potential. They found that the damage was no worse in people who lived near a cell phone tower as compared with those didn’t.

The amount of exposure from living near a cell phone tower is typically many times lower than the exposure from using a cell phone. About 30 studies have looked at possible links between cell phone use and tumors in people. Most studies to date have not found a link between cell phone use and the development of tumors, although these studies have had some important limitations. This is an area of active research. For more information, see Cellular Phones.

Studies done in the lab

Laboratory studies have looked at whether the types of RF waves used in cell phone communication can cause DNA damage. Most of these studies have supported the idea that the RF waves given off by cell phones and towers don’t have enough energy to damage DNA directly. Because of this, it’s not clear how cell phones and towers might be able to cause cancer, but research in this area continues.

Some scientists have reported that RF waves may produce other effects in human cells (in lab dishes) that might possibly help tumors grow. However, these studies have not been verified, and these effects weren’t seen in a study that looked at the blood cells from people living near a cellular phone tower.

Several studies in rats and mice have looked at whether RF energy might promote the development of tumors caused by other known carcinogens (cancer-causing agents). These studies did not find evidence of tumor promotion, but this is still an area of research.

A recent large study by the US National Toxicology Program (NTP) exposed groups of lab rats and mice to RF energy over their entire bodies for about 9 hours a day, starting before birth and continuing for up to 2 years (which is the equivalent of about 70 years for humans, according to NTP scientists). The study found an increased risk of tumors called malignant schwannomas of the heart in male rats exposed to RF radiation, as well as possible increased risks of certain types of tumors in the brain and adrenal glands. But some aspects of this study make it hard to know just how these results might apply to RF exposure from cell phone towers in people. For example, there was no clear increased risk among female rats or among male or female mice in the study. The doses of RF radiation in the study were also generally higher than those people are exposed to when using cell phones (much less being near a cell phone tower). The male rats in the study exposed to RF waves also lived longer, on average, than the rats who were not exposed, for unclear reasons. Still, the results add evidence to the idea that the signals used in cell phone communication might potentially impact human health.

What expert agencies say

About cell phone towers

The 3 expert agencies that usually classify cancer-causing exposures (carcinogens) – the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), and the US Environmental Protection Agency (EPA) – have not classified cell phone towers specifically as to their cancer-causing potential.

The US Federal Communications Commission (FCC) has said this about cell phone towers near homes or schools:

“Radiofrequency emissions from antennas used for cellular and PCS [personal communications service] transmissions result in exposure levels on the ground that are typically thousands of times below safety limits. These safety limits were adopted by the FCC based on the recommendations of expert organizations and endorsed by agencies of the Federal Government responsible for health and safety. Therefore, there is no reason to believe that such towers could constitute a potential health hazard to nearby residents or students.”

About RF radiation

Some of the agencies that classify cancer-causing exposures have, however, made statements about radiofrequency radiation.

The International Agency for Research on Cancer (IARC) has classified RF fields 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.) IARC also noted that exposure to the brain from RF fields from cell phone base stations (mounted on roofs or towers) is less than 1/100th the exposure to the brain from mobile devices such as cell phones.

The Environmental Protection Agency (EPA) states:

“At very high levels, RF energy is dangerous. It can heat the body’s tissues rapidly. However, such high levels are found only near certain equipment, such as powerful long-distance transmitters. Cellphones and wireless networks produce RF, but not at levels that cause significant heating. In addition, RF energy decreases quickly over distance. At ground level, exposure to RF from sources like cellphone towers is usually very low.

Some people are concerned about potential health effects, especially on the developing brains and bodies of children. Some studies suggest that heavy long-term use of cellphones could have health effects. Other studies don’t find any health effects from cellphone use. Long-term studies on animals exposed to the RF found in wireless networks (Wi-Fi) have, so far, found no health effects. Scientists continue to study the effects of long-term exposure to low levels of RF.”

Can I limit my exposure?

Cell phone towers are not known to cause any health effects. But if you are concerned about possible exposure from a cell phone tower near your home or office, you can ask a government agency or private firm to measure the RF field strength near the tower (where a person could be exposed) to ensure that it is within the acceptable range.

What should I do if I’ve been exposed to cellular phone towers?

There is no test to measure whether you have been exposed to RF radiation from cellular phone towers. But as noted above, most researchers and regulatory authorities do not believe that cell phone towers pose health risks under ordinary conditions. If you have additional health concerns, you might want to talk with your doctor.

Cellphones and cancer risk: what to keep in mind

The question of whether cellphone radiation is linked to tumours remains inconclusive after the partial release of a $25-million U.S study on rats.

Researchers at the National Toxicology Program bombarded rats with cellphone radiation at extremely high power ranges and studied aggressive glioma brain cancer and rare, benign schwannoma growths of the heart.

In the preliminary results, “low incidences” of tumours were found in 2 to 3 per cent of male rats. Female rats weren’t affected.

Confusingly, after two years of testing, the control group of male rats who weren’t exposed to any radio frequency radiation lived shorter lives than those exposed.

Interpreting findings involving animals is challenging, and the results can’t be directly applied to humans. That’s part of the difficulty of determining whether something causes cancer.

Some of the study’s own reviewers had trouble accepting the results because of the quirks. 

“I am unable to accept the authors’ conclusions,” wrote outside reviewer Dr. Michael Lauer, deputy director of the National Institutes of Health’s office of extramural research. “I suspect that this experiment is substantially underpowered and that the few positive results found reflect false positive findings.”

The fact that the rats exposed to radiation survived longer than those that weren’t “leaves me even more skeptical of the authors’ claims,” Lauer wrote. Other study reviewers also raised questions about the way the study was conducted and its conclusions.

For humans, the World Health Organization’s fact sheet says: “No adverse health effects have been established as being caused by mobile phone use.”

The WHO’s International Agency for Cancer Research lists cellphone use and other radiofreqency electromagnetic fields as “possible” carcinogens, a category that also includes more than 260 other substances such as coffee, engine exhaust and talc-based body powder.

Distraction danger

“If cellphones cause cancer, they don’t cause a lot of cancer,” said Dr. Otis Brawley, the American Cancer Society’s chief medical officer. 

Brawley said people should be far more concerned about “distraction caused by cellphone,” which he said causes more deaths.

The toxicity question of cellphones is just half of the equation. Exposure is also key.

“I’m not particularly nervous about using my cellphone. On the other hand, from a public health point of view, this is an important issue,” said Paul Demers, a senior scientist in prevention, screening and cancer control at Cancer Care Ontario.

“Given how much everybody is using cellphones, there’s been a number of studies that have been carefully looking at brain cancer rates, and they simply have not been going up in any significant way.” 

Demers also said cellphone technology has improved to emit orders of magnitude less radiation than they did decades ago. In part, it’s because consumers want lighter phones with smaller batteries, he added. 

Some standard precautions to reduce exposure are:

  • Keep calls short.
  • Use hands-free devices.
  • Replace calls with text messages or video chats.

Parents should apply the same precautions to their children.

A 2015 report by the nonprofit group MediaSmarts suggested nearly a quarter of children in Grade 4 reported having their own cellphone. Ownership jumped to just over half in grade 7.

Matthew Johnson, director of education at MediaSmarts, said children aren’t using their phones to talk — more and more the devices are used to take photos and to text-message.

Texting could be a positive in that it further reduces exposure compared with holding a phone to the head, Demers said. 

The National Toxicology Program researchers plan to release further findings on other parts of the body and in mice by fall 2017. Those findings also need to be carefully replicated to check their reliability and validity. 

With files from Associated Press and CBC’s Christine Birak