Can WiFi cause cancer?

WiFi operates in the 2 to 5 GHz range - part of the microwave portion of the electromagnetic spectrum. This is in the same part of the spectrum where cell phones operate so I may refer to WiFi or cellphone electromagnetic radiation interchangeably. These are radio waves - no different than those used to broadcast television programs - except that they are higher in frequency. They aren't nearly as high a frequency as visible light - and no one worries about getting cancer from visible light (ultraviolet light, on the other hand, causes skin cancer - but this is the minimum energy necessary to cause ionizations that can cause breaks in strands of DNA - which is the mechanism by which cancer cells can be created). There is no credible evidence that non-ionizing radiation has any adverse health effects at all. There is no radiobiologic mechanism that could explain such an association - and absolutely no scientifically valid evidence that this has ever happened.

Dr Garry Larson MD, Medical Director- Procure Proton Therapy Center OKC states that he has treated patients with cancer for over thirty years as a board certified radiation oncologist and he is familiar with every carcinogenic agent known to man - He is with absolute certainty that radio waves cannot harm you (unless perhaps you were in the path of a multi-megawatt microwave beam in which case they might cook you - but as far as he knows, there is no likelihood that this danger even exists).

There has never been (and will never be) a randomised trial assessing the cause and effect relationship between radio frequency emissions and neoplastic disease. In order to have a randomised study, half of the randomly selected subjects would need to avoid cellphone use and that's not going to happen.

Humans have been exposed to man-made radio frequency radiation for over 100 years and we have always been exposed to microwave radiation from the Cosmos.

For example, the latency period for radiation induced malignancies is, on the average say 20 years, but epidemiologic studies of large groups of people (that only require a few thousand patients to reach stastistical significance) exposed to ionizing radiation start showing an increase above baseline by seven years. So conservatively, there should be at least a few excess cases of glioma, caused by cellular (or WiFi) electromagnetic radiation by now.

See this reference which looks at all the reported cases of gliomas caused by ionizing radiation (where we have a plausible explanation for cause and effect). Millions of people have received brain irradiation and only 73 cases of radiation induced gliomas have been reported.

A Report on Radiation-Induced Gliomas

We do have evidence that cellphones (or WiFi) do NOT cause an increase in brain tumors. Look at the time period over which cellphone use became common - say over the last twenty years. During that time, the incidence of brain tumours has remained absolutely flat. With over four billion people using cellphones (or WiFi) today, if there was any influence on the development of brain tumors, we would be seeing that by now.

The data from the National Cancer Institute below shows no increase in the incidence of primary brain tumours over the period of time that cell phones have been in use.

Say someone found a potential association between carrying coins in your pocket and the risk of a particular type of tumour. It would set off a frenzy of activity among a group of people who were convinced that this association was real. They would lobby for a law requiring that warning signs be placed on change machines. The effect would snowball until some people would demand that the government stop minting coins.

So lets review

There is no biologic mechanism to explain why non ionizing radiation (like the cellphone's emission of radio waves) could induce any type of tumour
We do have a mechanism to explain the association between ionizing radiation and tumour induction, but out of millions of people who have received radiation therapy to their brain, only 73 radiation induced gliomas have been reported in the world's literature.
For radiation induced neoplasms in general, epidemiologic studies can show an increase in the likelihood of tumours with only a few thousand people over a time period less than ten years

At least something on the order of millions (if not billions) of people have used cell phones for over two decades now and there is no evidence that the incidence of brain tumors has increased over that time period
Now lets get down to why this sort of irrational belief takes hold and, among other things, prompts five questions on this subject (at least that I have seen) in the time that I have been reading Quora (less than two months).

We have essentially no control over whether we live or die - except that we should avoid dangerous behaviours like smoking, becoming obese, not wearing seat belts, texting while driving, etc. Otherwise, over a trillion cells carry on countless biochemical processes that we have no control over. One out of four people will get cancer - beyond avoiding foolish behaviour, we can't influence that risk.

Since we have this subconscious, ever present fear of death (see below*), we employ magical thinking to give us a false sense of power over it. When we create artificial threats to our survival in our imagination - and then avoid practicing behaviours that make us vulnerable to those threats - we feel we have some power over whether we live or die. These are also know as superstitions.

Primitive cultures made sacrifices to imaginary gods so they wouldn't destroy their village - Children learn to avoid stepping on cracks - The germaphobe may engage in compulsive hand washing - and some people avoid putting their cellphone right next to their skin.