There's a lot of bad "science" floating around about radio frequency and electromagnetic field exposure from Wi-Fi routers and the wireless network that your iPhone accesses. AppleInsider delves into the subject, and the actual science behind it.
First and foremost, RF radiation is not the same as ionizing radiation generated by decay of radioactive isotopes, and from the sun itself. This isn't Radiation Physics 101 in 1000 words, so in short, RF lacks the energy that ionizing radiation has to break chemical bonds, ionize atoms, and damage DNA.
Sufficiently high levels of RF radiation can heat tissue and could theoretically cause tissue damage. But, these levels aren't reachable by the public, assuming safety standards are maintained, and the only people that need to be worried about them are generally workers in extremely close proximity to a transmitter.
Without delving into a basic physics lesson about time, distance, shielding, and wavelengths, that microwave in your kitchen is probably 700W. It is focused on the area below the emitter, and shielded by the microwave's structure itself.
That Wi-Fi router that's in your house? It is probably a single watt, with that entire watt diffused over the entire broadcast area.
It's okay if you don't believe us, even though this writer has a background in practical exposure control. Read what the World Health Organization has to say about it, and if you don't want to do that either, here's the takeaway:
Considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that the weak RF signals from base stations and wireless networks cause adverse health effects.
That iPhone in your pocket
And regarding your cell phone? That's really no different. The combination of the frequency, the fact that it's not broadcasting at full power constantly, and the low levels of emissions do not produce any noticeable heating effects at all. So, as a result there are no known adverse health effects.
The US Food and Drug Administration has been running studies for 15 years on the topic. The FDA points out that there have been some studies showing minor effects from the devices, but they aren't reproducible. Both the FDA and WHO note that given the profoundly low levels of energy involved, it is nearly impossible to eliminate other causes producing the biological effects in the studies that did find an effect.
For some time a number of individuals have reported a variety of health problems that they relate to exposure to electromagnetic fields, or radio frequency radiation. While some individuals report mild symptoms and deal with it by with avoidance, others claim to be so severely affected that they alter their lives to deal with the problem.
This reputed sensitivity to EMF has been generally termed "electromagnetic hypersensitivity" or EHS. But, the scientific studies on the syndrome show that those afflicted have no greater detection of RF fields by symptoms than a user not complaining that they have the syndrome.
The WHO believes that prevalence is "a few individuals per million." Current scientific theories on it suggest that a strobing from CFL bulbs, poor air quality, or either pre-existing psychiatric conditions or new ones induced by stress cause the problem, rather than exposure to RF radiation.
The radiation exposure industry has an acronym "ALARA" — it stands for as low as reasonably achievable. Workers are trained to maximize the distance from a source, maximize the effect of any available shielding, and minimize the amount of time spent in an environment with exposure.
For RF, distance is covered as long as you don't have a 5G commercial broadcast transmitter or an Aegis radar assembly from a Navy cruiser on your bedroom wall pointed at you. Shielding is mostly a non-issue as the radiation isn't ionizing. And, the heating effect from normal consumer goods use is negligible, so time isn't even a factor as the 0.01C that your ear skin is increasing because of that long phone call to your grandmother doesn't do anything.
In the case of occupation exposure, limits for trained workers are generally set at 10 percent of whatever is considered a "safe" limit. Limits for the general public are normally 1 percent of that safe limit, or much less. In the case of RF, the Specific Absorption Rate (SAR) limit depends on how the measurement is made, but is most restrictively 1.6 watts per kilogram. An iPhone X has a SAR of 1.19 in a worst-case measurement situation at maximum transmission power. If that phone is moved a quarter-inch from your head, then the SAR drops to about 0.6 W per KG.
A wireless router is worst case 0.02 watts per KG at about six inches away from the device, and drops dramatically with distance. Those 50 wi-fi networks you can see from your computer? You're probably looking at a total of 0.1 watts per KG from all the sources combined.
Are you in utterly and absolutely zero danger from RF or EMF? Scientifically, there is no way to exclude the possibility absolutely — but you're in some form of danger every minute of every day from one thing or another.
To put things in perspective, you are in far, far more danger from a lifetime exposure to the ionizing radiation produced by the radon gas in your basement or from getting cancer from sun exposure, than you are from living in the same neighborhood as a cell tower, with twenty Wi-Fi routers surrounding your chair, and actively talking to somebody on 5G on your iPhone with it velcroed to your head for that whole life. And, the risk from the radon-laden basement is relatively low.
If you're still worried about it, don't sit on your router, and use your speaker function on your iPhone.
Studies continue, and will until the sun blacks out, because people are very bad at risk assessment even when given the data. But, science is true if you believe it or not. So, use that router, and get that mesh network going without fear. Break out the cell phones, and don't worry about using them.