When I started writing this blog I intended to give you some information about how the ever increasing number of wireless devices we’re surrounding ourselves with may impact our health. I’m sure you’ve seen lots of stories in the press detailing a wide variety of disorders linked to Wi-Fi or mobile phone usage. And I must admit that as a result of these stories I was always wary of keeping my phone in my pocket, making long calls without my hands-free kit, or sitting with my laptop on my lap.
However, when I started reading around I was amazed that this story still seemed to have traction given that no harmful effects in humans have ever been demonstrated. Indeed, the whole area seems to be a great example of certain parts of the media, and some scientists, over-interpreting findings to produce a good headline/story.
But before I delve into how this over-interpretation is occurring I should provide a bit of background so you can understand why you really shouldn’t worry about your Wi-Fi or mobile phone.
What is the Electromagnetic Spectrum?
The electromagnetic spectrum (EMS) is the collective term for all known electromagnetic frequencies (EMF), which can range from the very high frequency gamma rays, often associated with nuclear reactions, down to very low frequency radio waves and beyond. The spectrum incorporates all kinds of frequencies including X-rays, ultraviolet light, visible light and the microwaves and radio waves which Wi-Fi and mobile phones use to transmit data. For more info the World Health Organisation have a great page detailing EMF.
EMF are defined by three characteristics; frequency, wavelength and energy, how they interact is shown in the image below, but I’ll also give a brief description for each as well (also the numbers can get very large, so at the bottom of the post I’ve made a table detailing how the various units relate to each other).
As wavelength decreases, frequency and energy increase. EMF can only direct damage DNA when it is said to be ionizing, which occurs in the UV range and above. Which is why long-term exposure to the sun is linked with skin cancer. Below this point EMF can only induce a biological effect by exchanging energy with atoms and molecules within our cells, a process that leads to heating.
Wavelength is the easiest of three measurements to understand and simply refers to the distance between two peaks within a wave and is measured in metres (m).
A simple way to picture this is to imagine yourself standing on a beach watching the waves coming in. You can see the peak of two waves, the distance between them is the wavelength.
Frequency is a bit more difficult to get your head around, but at its simplest refers to the number of occurrences of an event in a given period of time. So, the more often something occurs the higher frequency it is said to have.
When talking about EMF this relates to the measurement of the number of wave peaks at a set point in a given time; this is typically in one second as is measured in hertz (Hz). So 1 Hz would refer to one peak every second, 1 kHz (kilo-hertz) would be a thousand peaks per second and 1 mHz (milli-hertz) would be one peak every thousand seconds.
Wavelength and frequency are related, a long wavelength goes hand in hand with a low frequency and vice-a-versa. Let’s use our beach metaphor to visualise this again. Say it’s a calm day and the waves are spaced far apart (i.e. have a long wavelength), if you count the number that break on the shore in 10 seconds it would be quite low (i.e. low frequency).
Now imagine the weather changes and it becomes stormy, the waves are much closer together (i.e. have a short wavelength), so if you counted the number of waves breaking in that same 10 seconds it would be much higher (i.e. high frequency).
So finally, to energy, which for the purposes of this blog is the most important factor as it is the transfer of energy from EMF waves into the body that has generated health concerns. Energy in EMF is directly linked to wavelength and is usually measured as electronvolts (eV). The higher the energy the shorter the wavelength and the higher the frequency.
Our beach example doesn’t work here as you can have short wavelength waves with lots of energy, or little energy. With EMF energy and wavelength are always linked. So the energy of a single EMF wave from a candle is the same to the energy in an EMF wave from the sun. There are just many, many more EMF waves coming from the sun.
Bringing it all back together
So now we know the three measurements of EMF lets have a look at some examples:
|Gamma Rays||~300 EHz (exa-hertz)||~1 pm (pico-metre)||~1.25 MeV (mega-electronvolt)|
|Visible Light||400 to 800 THz (tera-hertz)||380 to 750 nm (nano-metre)||1.65 to 3.25 eV|
|Microwaves – A subgroup of the EMS which contains a lot of wireless devices|
|Microwave Oven||2.4 GHz (giga-hertz)||12.5 cm (centimetre)||10 µeV (micro-electronvolt)|
|Wi-Fi||2.4 GHz (giga-hertz)||12.5 cm (centimetre)||10 µeV (micro-electronvolt)|
|Mobile Phone||850 to 1950 Mhz (mega-hertz)||35 to 15 cm (centimetre)||3.5 to 8 µeV (micro-electronvolt)|
I’ve highlighted in red the major cause of health concerns. Wi-Fi and microwave ovens emit the same EMF and mobile phones are very close to this emission also.
Power, direction, distance and penetration
Microwaves are a type of non-ionizing radiation which exist within the EMS. Non-ionising means that they do not contain enough energy to ionize an atom or molecule i.e. remove an electron from it. They only contain sufficient energy to excite atoms which manifests as the targeted object warming up.
This is important as straight away we can say that microwaves do not contain enough energy to directly induce the DNA damage required for the development of cancer.
But can they do it indirectly by heating up the tissue resulting in DNA damage or other effects? Well lets have a look at how a microwave oven functions and work from there.
Microwaves heat food by converting electricity into microwaves through a device called a magnetron. This high power device uses a lot of power to generate these microwaves, typically between 800 and 1,000 watts, and these waves are focused directly onto the food using a device called a wave-guide.
The high-energy microwaves pass through the food and because microwave ovens are coated with a reflected lining they bounce back and pass through the food again. Each time the wave passes through the food it transfers an amount of energy to the food heating it up. Great for heating up your food, not so good for you which is why microwaves are heavily shielded. So, if microwaves are so great at heating up food, how are they safe to use in Wi-Fi and mobile phones?
Well the answer lies in the heading to this section; power, direction, distance and penetration:
As mentioned above microwave ovens use about 800-1,000 watts to emit their microwaves. Wi-Fi base stations at a maximum are limited to 1 W in North America and 100 mW in the European Union. However, most base-stations will operate at or below the 100 mW EU limit to allow their sale globally. Wi-Fi transmitters contained within devices such as laptops or phones operate at even lower powers in order to preserve battery life.
So, just to play devil’s advocate lets take the worst-case scenario. A 1 W Wi-Fi base station is 800-1,000 times less powerful than your microwave oven. So, that ready-meal that takes 5 minutes to heat up in the microwave would take between 65-85 hours to heat up using the antenna from your base-station. If we use the more real-world measurement of 100 mW you’re looking at 650-850 hours or 27-35 days.
In other words it’s a lot less powerful. The counter argument then comes along that you don’t have your microwave going 24 hours a day, every day of the year. It’s a good point, but then the next two issues come into play.
The microwaves generated in your microwave are focused onto your food using the wave guide, with little to any material sitting between them, and are also able to reflect around the interior. Wi-Fi and mobile phone antenna do not work in this way. Because, they don’t know where you’re going to be sitting relative to the receiver the antenna is designed to broadcast in every direction. So rather than being focused on one point, that 100 mW of power is actually being broadcast in every direction. Even sitting directly on top of your Wi-Fi base station would therefore expose you to half of that 100 mW, and I don’t know about you but I don’t often sit on my router. Which leads us to the next point.
In your microwave oven the food is located a few centimetres away from the microwave source, and there is often little if any material located between the two. Now compare that with your Wi-Fi base-station. Mine is located about 6 m (20 ft) from where I’m sitting now, and there are two walls sitting between me and it. My mobile phone is sitting on the desk in front of me, but isn’t really emitting much as it’s not making a call and its Wi-Fi transmitter is operating at a very low level.
This is important as microwaves, as with all kinds of EMF, are subject to something called the inverse square law. It sounds complicated, and I won’t go into the maths but the basic principle is that there is a rapid reduction in signal strength as you move away from the emission point. As a simple example the lets say the amount of energy reaching a certain area 1 m away from the transmitter is 1 eV. At 2 m this would be 0.25 eV, at 3 0.1 eV etc… Which leads us onto the final point.
Microwave ovens have been designed to be high power (at least 800-1,000 times more powerful than your Wi-Fi base station) and to focus all that power onto the food at a short distance. And even then the heating effect is limited to the upper portions of any solid (estimates vary but it is generally assumed to be a few millimetres at most). With the remainder of the heating effect coming from conduction of heat. [1,2]
The final comparison
To summarise, microwaves are non-ionizing and so cannot directly cause DNA damage. Any effect must come from their ability to heat body tissues up. The microwaves emitted from your Wi-Fi base station or mobile are emitted from a low power transmitter, in every direction over large distances and can only transmit energy to the top few millimetres of the body. Therefore, any heating effect will be very small, and will be limited to the top few millimetres of your skin. It is hard to see at this point how there can be any adverse effects associated with Wi-Fi or mobile phone usage in people.
But what about all these studies?
Well if it’s so hard to see an effect why are there so many studies which show one?
Well are there?
I did a lot of reading around for this blog post and I was not able to find any study which showed an effect in people using real world conditions. For example, this study describes how Wi-Fi decreases human sperm motility, leading many people to make a link between Wi-Fi and male infertility. But, the study was performed on sperm outside the body exposed directly to a Wi-Fi transmitter a few millimetres away . Does that sound like a real world scenario to you? Being sedentary and sitting down with your laptop on your lap is much more likely to be harmful than the microwaves emitted by your laptops Wi-Fi, although this in itself is tricky to measure due to difficulties in describing a sedentary lifestyle .
Or lets take this study which describes DNA damage in rat brains in response to microwave radiation. It’s very interesting research but again has been massively overinterpreted. The dosage received by the animals is 1 W/kg. The average westerner weighs about 75 kg so this is equivalent to a 75 W transmitter (remember 1 W is the absolute maximum and that is emitted in every direction) sitting immediately adjacent to a person (remember that signal strength decreases rapidly with distance). Again, does this sound like a real world scenario? 
If someone is able to point towards a study which shows an effect under real world conditions I would be very interested in reading it. But, I wasn’t able to find any myself. As we started with them lets give the final word to the World Health Organisation:
In the area of biological effects and medical applications of non-ionizing radiation approximately 25,000 articles have been published over the past 30 years. Despite the feeling of some people that more research needs to be done, scientific knowledge in this area is now more extensive than for most chemicals. Based on a recent in-depth review of the scientific literature, the WHO concluded that current evidence does not confirm the existence of any health consequences from exposure to low level electromagnetic fields. However, some gaps in knowledge about biological effects exist and need further research.
Taken from WHO, What are electromagnetic fields
So I shouldn’t worry about EMF?
Well you shouldn’t worry about the EMF in relation to Wi-Fi or your mobile phone but certain parts of the EMS can be very harmful, and there are some regions to which we are frequently exposed. Short wavelength UV is ionising and can directly damage DNA, UV of a longer wavelength is not ionizing but can break chemical bonds releasing free radicals, both of which can lead to the development of skin-cancer. A major emitter of UV radiation? The sun! So, the energy you were using worrying about EMF from Wi-Fi and phones, focus that on preventing your exposure to UV instead.
Getting your head around these scales can be difficult. The above table lists all the common prefixes and how they relate to the base. If we use metres (m) as an example we can see that 1 km (kilo-meter) would be 1,000 meters. Whereas 1 µm (micro-meter) is 1 millionth of a meter.