Does WiFi pose health risks? -

Does WiFi pose health risks?

If you fear WiFi, you may also want to steer clear of baby powder


Viktor Hertz/Flickr

Radiation can give life and take it away. Sunlight, therapy to kill malignant tumors, powerful x-rays, and radio waves are all forms of radiation. Lately, much has been made of the health risks related to another source of invisible waves: WiFi.

In recent years, politicians and leaders in the health field have tried to do something about the perceived threat of exposure to radio-frequency (RF) electromagnetic fields, on which WiFi, cell phone networks, radio signals, microwave ovens, and cordless home phones depend. Public fears about RF fields may have hit a fever pitch when, last summer, the World Health Organization designated them as a “possibly carcinogenic” agent—alongside others like coffee—for which evidence of harm is uncertain. Since then, we’ve heard our nation’s doctors raise concerns about the health risks related to cell phones; politicians, such as Elizabeth May, warn publicly about the potential harms posed by WiFi; and frightened parents say they’d move their children away from the invisible threat, as schools impose bans on wireless internet.

But what do we actually know about the health effects of RF exposure—and, in particular, the health risks related to WiFi?

Different technologies give off different amounts of radiation, explained Dr. Patrizia Frei (PhD), a research fellow at the Swiss Tropical and Public Health Institute, who has conducted reviews on the health effects of RF exposure. “While mobile phones cause mostly localized exposure to the head,” she said, “WiFi usually causes far-field whole-body exposures which are usually much lower.” According to the UK’s Health Protection Agency, “the signals are very low power, typically 0.1 watt (100 milliwatts) in both the computer and the router (access point), and the results so far show exposures are well within the internationally-accepted guidelines from the International Commission on Non-Ionizing Radiation Protection.”

The agency also goes on to note that the frequencies used in WiFi are similar to those from FM radio and TV, and that RF exposure from WiFi is likely lower than that of mobile phones. A review of the evidence on wireless technology and health outcomes by Public Health Ontario stated, “Wi-Fi exposure are not only well within recommended limits, but are only a small fraction (less than one per cent) of what is received during typical use of cellphones.” (Read more on different types of RF exposures here).

Singling out WiFi as a threat, in isolation from other (higher intensity) RF sources, then, seems quite science-ish. And those who banned WiFi in schools should consider dumping radios, cell phones, TVs, and—why not?some of the WHO’s other “possibly carcinogenic” substances, like coffee and baby powder.

Back to the science…

Let’s discuss what we know about RF exposure. The short answer: We have a pretty big pool of evidence to draw on, but the science is still working itself out and there are a number of methodological hurdles to overcome with regard to this type of investigation.

For starters, much of the research into the health effects of RF has focused on cell phones and brain tumors. The consensus here is that overall, there is no increase in the risk of glioma or meningioma with cell phone use, but there is evidence to suggest an increased risk of glioma at the highest exposure levels, which is part of the reason why the WHO’s International Agency for Research on Cancer (IARC) has said RF exposure is possibly cancer-causing in humans.

There’s less material on WiFi, even though, as noted, RF exposure from this source is lower than that of cell phones. For now, Dr. Joachim Schüz, head of the section of Environment and Radiation at the IARC, summed it up for Science-ish: “No adverse health effects in relation to (WiFi) exposure have been established.” (His sentiments are echoed by Health Canada and UK’s Health Protection Agency.)

But the dearth of good evidence about adverse health effects doesn’t mean we are in the clear. All the data we have are fairly new, since these technologies have only been ubiquitous for the last 10 to 20 years, and the way we live with them is rapidly evolving. When it comes to chronic diseases like cancer, Dr. Schüz noted, “induction periods between exposure and the onset of disease may be very long.”

Furthermore, there is no established biological mechanism for how RF fields at low levels would lead to adverse health effects. “Hence studies showing no effect only provide evidence against certain assumed mechanisms but it is difficult to rule out any possible effect,” said Dr. Schüz.

Lastly, there are the notable methodological limitations when it comes to the research into RF and its effects in humans. On cell phone studies, Dr. Frei noted that most so far have used a case-control design: researchers ask people with (cases) and without (controls) brain tumors about their mobile phone use in the past. “Do you remember when you started using your mobile phone for at least once a week?” Dr. Frei asked, noting that people with a brain tumor might be cognitively impaired and therefore have even more difficulty remembering. Other studies that looked at cell-phone subscription records have their flaws, too. “We do not have information on the use of an individual, we just know when they got or bought a mobile phone. So there are still limitations with regard to exposure assessment.” Plus, most of us live with so many RF sources, it’s difficult to study populations by levels of exposure.

Nonetheless, Dr. Schüz said he would not recommend banning Wifi from schools based on the evidence we have. But he suggests there’s no harm in taking a precautionary approach where possible. For example, “Heavy mobile phone users can use hands-free devices to reduce exposure to the head, base stations of cordless phones can be placed outside the bedroom a hands-free devices to reduce exposure to the head, and keep base stations of cordless phones outside the bedroom.” Science-ish would add: Be wary of conclusive answers and fear-mongering on this subject. It’s a new and evolving area of science.

After my year-end call for submissions, you told me you were most concerned about two things: whether WiFi poses health risks, and which is the most effective diet for losing weight, based on the evidence. Stay tuned for the second installment on diet next week.

Science-ish is a joint project of Maclean’s, The Medical Post, and the McMaster Health Forum. Julia Belluz is the associate editor at The Medical Post. Got a tip? Seen something that’s Science-ish? Message her at or on Twitter @juliaoftoronto


Does WiFi pose health risks?

  1. Hi, Julia: A couple of absolutely crucial points.

    The first is that the radiated power of a mobile phone and a Wi-Fi base station are microscopic compared to other sub-light RF sources. E.g., land mobile radio base stations that a client of mine recently deployed put out 35 W when they’re keyed, about 2 orders of magnitude more than typically put out by a mobile phone. (And I understand that long-term studies with folks who work near high-power transmitters hasn’t found elevated cancer rates, anyway.)

    Your brain can be hit with a SAR in bright sunlight much higher and longer than a cellphone  – and our bodies are used to dealing with it (i.e., by moving the blood around to cool the brain).

    Finally the square-cube law is always forgotten. The radiation density drops as a cube of the distance from the transmitter (more or less; the waves don’t expand in a perfect sphere, but it’s a good guide). In other words, if the SAR from my mobile is 1 W/kg 15 mm from my head it’ll be around 1/8 that at 30 mm – and so on.

    I’ll admit that the Wi-Fi scare is the one that gets me. The idea that barely detectable radio waves in the sub-light spectrum could be harmful is so out-of-the-box idiotic I find folks like Eliz. May despicable in their scaremongering. We shrug at infinitely higher risks (like driving!).

    • I’m not at all arguing that Wi-Fi is unsafe, but the problem lay people face is which “experts” if any should we trust to assess the risks?

      In the past we’ve been assured about the safety of smoking, DDT, PCB’s and substances we slathered on our skin but were later found to pose unacceptable risk and withdrawn from the market. How often have we heard that exposures “are well within the internationally-accepted guidelines” only to have that change as more is discovered?

      • I would suggest the challenge (in this case)  is more technical than ethical.  From the article:

        There is “no established biological mechanism for how RF fields at low levels would lead to adverse health effects “.  

           For someone like me, this sounds amazingly reassuring. i.e. A bunch of really smart, qualified people cannot even develop plausible routes for low-level RF to cause danger.  However, as Julia points out this also means that researchers cannot systematically rule out those routes. Furthermore for a technology such as public Wi-Fi (where the public is exposed without consent, or even necessarily notice) even minor increasing in rare events are likely to be seen as unacceptable.  So you are left with what Julia describes as case-control type of study which are notoriously unreliable and virtually guaranteed to  lead to false positives.  (If you study a small enough population for enough different rare events something unusual is bound to pop up.)

        This does not mean that Wi-Fi is completely safe.  It means nobody could possibly prove (or know) that Wi-Fi is completely safe.  What we do know is that there is not a plausible mechanism for it to be dangerous that is yet known.

        btw:  I always feel the title for Julia’s blog works on multiple levels.  Although it is extremely important and the people who conduct is are extremely talented, most medical research is still alarmingly primitive.

        • I was mainly reacting to Richard’s use of the word “idiotic” because I think it’s quite predictable that the public will be particularly confused about science in relationship to risk assessment. There are a lot of competing claims and counter claims and most of us don’t read scientifc journals or even reliable news sources.

          • Idiotic was the right word to use in that particular context.

    • Intensity drops as the square of distance not cube (it’s the surface area of the sphere at the distance it’s spread over).  But regardless, that is the reason the 35W emitter is less of a problem, it’s two orders of magnitude more powerful, but also orders of magnitude farther away than the phone by the head. 

      When it comes to wifi the biggest concern if there is a concern would probably be using a mobile device in your lap for long periods of time.  moving said device as far away as a table in front of you would go a long way to reducing any possible exposure (if it matters)

      • Even better, the skin depth associated with Wi-Fi radiation passing through aluminum is on the order of a micron.  This means that even a single layer hat should be sufficient.

    •  Thanks for thoughtful comments. Wanted to add something that Dr Joachim
      Schüz, Head, Section of Environment and Radiation at the International
      Agency for Research on Cancer (IARC), told me after I published this
      post. I asked him “Can we apply science on human effects from other,
      even older RF sources?”

      He said: “Especially looking at environmental RF from transmitters
      exposure is ubiquitous for decades, given the coverage by for instance
      TV and radio, and while the new technologies use different frequency
      ranges or modulations, investigations of earlier sources are still
      informative. When it comes to cancer, there are some studies in
      vicinities of strong broadcast towers (with output power in the Megawatt
      range) and in occupational settings. Overall, there is little evidence
      of increased cancer risks. Other endpoints have rarely been studied.

      “So the major new RF exposure is cell phones, as the transmitter is held
      directly to the head and this leads to exposure orders of magnitude
      higher than from environmental sources. Again there is a BUT: there are
      few studies on RF before the introduction of cell phone networks,
      presumably because it was not a topic of concern, so probably less data
      on health effects available than one would wish to have.”

    • Labeling people who disagree with you as “idiotic” or “despicable” says more about your egoism and your closed mind that it does about them.  Just remember that the limits of your knowledge is not the limit of what there is to know.

  2. Great post; Canada needs more Science-ish!

  3. What do we know about Wifi?
    Not nearly enough.

    • If by that you mean “not nearly enough to justify restrictions,” then I’ll assume you read the article. 

      • Two important considerations:

        1. Follow the precautionary principle.

        2. Follow the  money.

  4. I just found out this morning that conclusive evidence exists that at least a sub-set of people exposed to Wi-Fi are at significant risk to elevated levels of cholesterol (the wrong kind), indigestion, acid reflux (known to contribute to throat cancer)  and obesity.

    • Correlation or causation? Links to evidence of such?  Data?

    • this is obvious. Those people are in bad shape.

  5. One serious error of note here is that the frequency of wi fi is not that of radio or television but the exact same frequency as a microwave oven– 2.45 GHz
    would you sit your child in front of a microwave oven that was on for 7 hours / day?  There are a number of studies now on wi fi specifically that confirm biological and cognitive changes but there are thousands of studies that relate directly to exposure to pulsed microwave radiation from other sources that are similar to wi fi and can be used to draw well founded conclusions about the safety of this technology.  This technology is about two things,  money and surveillance.  It is a fraud and was sold to schools and is entirely unnecessary.

    • 2.45 GHz is classified as non-ionizing radiation.  i.e. at 2.4 GHz the energy per photon is about 10-5 eV i.e. 100,000 times less than the energy required to break a chemical bond.

      For ionizing radiation (i.e. UV, Xrays), we clearly need to worry about cumulative exposure, since a single photon is capable of generating (a small amount) of permanent damage.

      That does not mean that non-ionizing radiation is completely harmless, but it does mean that the actual power levels are important.  Probably the most credible mechanism for damage at this frequency would be due to the electric fields interacting with nerve tissue.  The magnitude of the electric fields associated the radiation go as the square root of the power. i.e. a source that was 100 times weaker would produce fields that were 10 x smaller.  So if you want to reference studies from other sources you do have to consider power levels.

      btw I am actually pleased that WiFi works in a part of the spectrum absorbed by water, it means most of the radiation is absorbed by my skull before it reaches my brain.

      • What effect would electric field have on nerve tissue? 

    • Keep in mind that a microwave oven is designed to emit about 9000 times more intense radiation than any wifi device. Try cooking anything with that.

  6. I’m a Professional Chemist who conducts human health and ecological risk assessments for a living. When encountering a new threat the first step is to propose a biological mechanism for action and to do so you look for a mode of action. Wifi are low powered microwaves. Microwaves on non-ionizing radiation and the primary mode of action of microwaves on biological tissues are thermal (microwaves heat water in tissues). Next we look at comparable sources of thermal excitation on human tissues (in this case the brain). Human tissues are extremely resistant to thermal effects and on a daily basis humans encounter substantially larger exposure to heat in their brains through dangerous activities such as drinking tea, walking up a set of stairs or the big one….wearing a toque. At this point one can comfortably abandon the blind application of the precautionary principle and be more discerning in our assessment.

    While it is possible that some secondary effects of Wifi may exist in extreme cases, human exposure to microwaves are well understood. Low-powered microwave radiation in the form of Wifi signals simply do not pass the smell test for any rational fear. Let’s worry about real threats to our health and ignore the phony scares out there.

  7. I would love to sue bell for my headaches.

  8.  ihavealreadycome.2 나는이미왔습니다.

  9. What I don’t like is being exposed to multiple layers of Wi-Fi, 24/7. I live in downtown Toronto and there is no escape. All of my neighbours leave their routers powered on 24/7. I can pick up 8 different private routers in my bedroom, plus there is the ubiquitous stuff floating around from commercial sources. This means I am constantly being “cooked” from multiple sources, and I cannot escape it. Seems to me this is similar to the threat of cigarette smoke — the smokers pump it out, the health-conscious cannot escape it. Perhaps there needs to be a concerted effort on the part of media to educate people to turn their routers OFF when not in use, especially at night. And we need much more research into this area.

    • Good point, especially as scientific opinion tends to ignore the pervasiveness of Wifi and the  near-constant exposure for some. I spent some time in a Wifi-d  building not long ago and felt ill by the time I finally got outside again and walking in the fresh air.

      • Maybe it was something else in the building that bothered you? Could be any number of things including your own imagination.

        • EMF pollution comes from many sources. WiFi, cell phones, SmartMeters, etc. The latter are the worst.

    • Let’s try a simple test to see how much you are being “cooked” by your neighbour’s WiFi signals. Take a glass of water, put a thermometer in it and leave it overnight on your counter. Since the microwaves from WiFi heat water I’m going to guess that when you wake up tomorrow morning you will find the water is 10-20 degrees warmer than room temperature….that will prove it to us? Oh wait…maybe the water will remain at room temperature? Once you have considered the observed water temperature in your glass try scaling up the model. Considering that a typical 60 Kg human has about 40 kg of liquid water as part of the mass I’m going to suggest that the only “cooking” going on is in your imagination. 

      • The key point here is the “long term” effect. Most people assume that because people aren’t dropping like flies, everything is safe.

  10. The terms “maybe” and “probably” are not definitive enough to allay concern and hardly scientific at all. The former USSR/today’s Russia banned microwave ovens in the 1980’s on the basis of scientific testing which was ignored by the West who had the biggest stake in manufacturing/sales.
    Playing it safe is still the best strategy, since manufacturing interests seem to trump consumer protection until enough people are killed or maimed to warrant condemnation.
    Not having overwhelming evidence to condemn WiFi at present doesn’t mean that there won’t be a huge “oops!” forthcoming and the inevitable backpedalling “we didn’t know…!”
    The “experts” have told us that smoking, non-breast-feeding, thalidomide, annual mammograms and water fluoridation were all just peachy. Somehow people seem to get suckered by the “it’s all scientific” punchline every time. This isn’t science, it’s Scientism.

  11. “exposures are well within the internationally-accepted guidelines from
    the International Commission on Non-Ionizing Radiation Protection.”

    I wonder about cumulative effects considering the article’s mention of cell phone networks, radio signals, microwave ovens, and cordless home phones.

    • I wonder about the effects of being hit in the head by someones thrown cellphone.

  12. If RF is not carcinogenic…

    Why would the United States have paid a settlement to a woman who got cancer working in the US Embassy in Moscow while it was being microwaved by the Soviets, at levels well below the safety limits established by the US? 

    Why would the Vatican be paying settlements to families of children who lived near their broadcast antennas who were found to be getting leukemia at 6 times the normal rate?

    The sad truth is that a vast majority of people:

    a) make money off the proliferation of wireless (RF) technology
    b) make money off the pharmaceutical “treatment” of illness caused by electromagnetic fields
    c) are addicted to wireless technology
    d) can’t imagine that something so ubiquitous is actually harmful
    e) are diagnosed as x, y, or z, are medicated and have no clue that they are actually suffering from electrosensitivity

    That leaves a very, very small minority of people who still have their health and sanity and have nothing to gain by shilling the industry-funded research, including that which comes from the ICNIRP.

    • So you say…. Provide some evidence to back up your claims.

      • SM did provide evidence. The examples of the U.S. and the Vatican paying compensation for radiation-related health problems are that evidence – regardless of whether you like it or not.  

        • The examples are claims and could be complete fiction. For it to be evidence  I would have to assume Smarter Meters never tells a lie or a fib and always reports things accurately and unbiased. 

          A few references as to where I can verify the claims would be a nice start.

          • So if one actually goes and reads up about the Vatican example you find that the radio towers in question produced electromagnetic radiation at levels above the legal limit. 

            And so goes down one claim in a ball of fire. No more needs to be said on this.

          • Those “claims” are news stories and easily verifiable. Have you heard of “Google” or any other search engine?

      • Do you need to be spoon fed?

  13. Cordless phones have been around over 20 years, cellphones have been ubiquitous for a decade or more. Brain cancers are rare. If there were any increased risk of brain cancer from cell phones, it would have shown up as a large spike in brain cancer incidence. But this hasn’t happened – if anything, rates have fallen. So if there is any risk from cellphones, it is tiny.
    Wi-fi is so much less powerful than cellphones, it would be absurd to extrapolate any risk, even if cellphones were found to be dangerous. The scaremongers are no more rational than if they heard that sunlight was dangerous and started a campaign to rid schools of lightbulbs.

    Craziest of all, though, are the anti-smart meter activists. Smart meters are wi-fi transmitters that are usually far from the body, and only transmitting for seconds a day. Yet to the critics it’s like they were being asked to sit in a microwave oven all day! From ovens to cellphones to wi-fi to smart meters, the amount of radiation drops by multiple orders of magnitude each time, but that doesn’t seem to matter to these people. Perhaps they got their ideas about the effects of dilution from homeopaths?

    No evidence of any risk. No plausible mechanism for any risk. The only mystery here is why anyone thought there was a problem in the first place.

  14. When it comes to Wi-fi, one of the pieces of research that lead to the classification of RF as a Possible Carcinogen in 2011 was a study by Univ. of Washington, sponsored by the U.S. Airforce & published in the renowned ‘Microwave News’ Journal in 1984.  It exposed rats to pulsed 2.4 GHz radiation i.e. the microwave radiation used as a beacon signal by wi-fi. It’s findings?  Exposures to low levels of pulsed 2450 MHz radiation cause a statistically significant increase in primary & metastatic tumors in rats.  In addition,  the experimental results suggesedt that microwave exposure is responsible for wide-ranging effects related to the adrenal glands and the entire endocrine system.  A preliminary study on Laptop exposure to sperm in 2010 found a decrease in sperm motility and an increase in DNA fragmentation.  The worry is that with wifi in schools, kids are increasingly sitting with laptops on their laps – for girls this is close to their ovaries, which already contain all their eggs for procreation.  Health effects appear to be frequency-specific, & pulsed radiation seems to be biologically more active.  A peer-reviewed, double blind provocation study using heart-rate variability in 2010, which used a 2.4 GHz cordless phone (same frequency as wifi) found that this radiation affects the Autonomic Nervous System (European Journal of Oncology) – the dramatic and repeatable response in this experiment was heart arrythmia and tachycardia for some subjects.  Mechanisms of causation have been put forward and are being investigated.  To my understanding these mechanisms seem to involve the essentially ‘electrical’ nature of the workings of our bodies, right down to the cellular level.  Dr Andrew Goldsworthy has put forward a mechanism, and also Dr Henry Lai for those who are interested.

    • P.S. Wi-fi occurs in the microwave range of radiation frequencies. ‘Microwave sickness’ was well-known from the first human exposure to man-made microwave which was in 1939 in the form of radar.  Natural microwaves from the sun do not penetrate to the earth, so the natural exposure for millenia on earth has been infinitesimal.  Also, man-made microwaves used by communication carriers like wifi are pulsed, which seems to be more biologically harmful.  We are currently conducting a huge experiment on life on earth.  Our exponentially escalating exposure to rf frequencies have far outpaced research on effects – epidemiological studies?? – they take decades & by the time the results come out, the exposure levels are redundant!

  15. I haven’t read ALL the comments to this article, but so far I don’t see anyone questioning the cumulative effects. We get radiation exposure from lots of sources in relatively small amounts, but over time what is the cumulative effect on our bodies?

    • Good question Rachel. It has been accepted for decades that ionizing radiation (x-rays, gamma rays, etc.) has a cumulative effect – but non-ionizing radiation (NIR) does not have this effect. In recent times, some people have made the claim that NIR is also cumulative. Someday we may find this is true. But, right now it is an unproven assertion, and only promoted by a few people with a history of alarmist claims.

    • Especially if you live in an apartment. My laptop picks up over 10 Wifi Signals. That stacking is kind of scary. If one router doesn’t cause cancer, maybe a crap ton of waves completely surrounding you from lots of other sources could.

  16. mmmmmmmmmmmmm cancer is good

  17. i love cancer

  18. cancer is your friend

  19. You might want to take a closer look at the effects of microwave exposure in-vitro. something like 20 years ago some researcher exposed cells that went on to divide but the dapi stained chromosomes were not evedent only little glowing balls. While the microwave intensity may have been too high the effect was very dramatic and clear. Check the science before dismissing cellphone microwave carrier wave impacts upon living cells

    • Our high school has just installed wifi through out the school. I have routers in my class room, this year I have experienced multiple headaches and many sleepless nights the only thing I can think of are these routers in my classroom. I am temped to file a complaint, we were not even asked. It feels as if my head were going to explode. Is it fair that some people are more suseptable than others?

  20. It’s becoming readily apparent that most people in this discussion try to associate the dangers of WIFI is being safer than stepping on a banana peel. Apples and oranges discussions. Tech industries stand to loose a lot if all this RF pollution is absolutely proven as unsafe. But guess what, the reports to come out but the faithful of the flock come out to defend the industry stance, time and time again. Guess what people, your defense of the technology will not protect you from it.

    We need third party research and not something regulated by specifically “governmental agencies.” You know, the people you are supposed to be able to trust (and who get caught lying time and time again).

    From WIFI to cell phones and now to SmartMeters, there are indeed health issues to be aware of. WiFi seems to be the weakest but each new revision of WiFi technology pumps out more and more juice. Oh! We get a lot of radiation from the Sun! We’re also getting it from leaking nuclear reactors, airborne high-altitude nuclear weapons tests, depleted uranium from military bombardments and who knows what else. WiFi and the other communications technologies are adding to the already saturated environment of full spectrum electromagnetic pollution.

    If you have questions regarding WiFi health, I wouldn’t go to government. Reference third party laboratories that aren’t funded by the big tech companies, as they may be more honest in their reporting.

  21. A point of reference is low level exposure to things like BPA, sodium fluoride and other “benign” chemicals. People say, “no big deal!” Well, we have learned that over time, evidence proves otherwise.