To a physicist, every moment of every day is filled with radiation.
As I sit here in my living room, I’m bombarded with radiation – thermal radiation from the heat of the day, visible light radiation from the Sun and various lights and displays in the room, radiofrequency radiation from my wireless router and cell phone, microwave radiation from my kitchen and from the radars of the aircraft on final approach to LaGuardia Airport, ionizing radiation from natural radionuclides in my body and in the bricks from which my building is constructed, more microwave radiation from the birth of the universe (the cosmic microwave background radiation), gravitational radiation from black holes and neutron stars halfway across the universe, and more.
What’s in a name?
To a physicist, all of this is radiation, distinguished primarily by the energies of each different type (ultraviolet is less energetic than gamma rays, visible light is less energetic than UV but has more energy than thermal radiation, and so forth. To a non-physicist, this sounds frightening and dangerous – so why aren’t the physicists worried?
For a physicist, “radiation” is used very broadly – to refer to the transfer of energy from one spot to another. The inside of a fluorescent light is coated with phosphors; these phosphors are energized by ultraviolet light emitted by mercury vapor inside the tube, and they give off this extra energy in the form of visible light radiation, just as radiofrequency radiation transfers excitation energy from electrons in an antenna to electrons in a distant antenna. But here’s the important thing – of all the different forms of radiation, it’s only the highest energies (UV, x-rays, and gamma radiation) that has enough energy to strip an electron from an atom, creating a pair of ions – and it’s this process of ionization that starts the whole sequence of steps that might lead to cancer in the following years or decades. Radiation that lacks the energy to cause an ionization cannot cause cancer, and only UV and more energetic, ionizing radiations are capable of ionizing atoms.
The thing is, most people, myself included, don’t tend to say “ionizing radiation” very often. I work with ionizing radiation for a living. When talking about “radiation,” it’s a pretty good bet that I’m not talking about gravitational, radiofrequency, thermal, or any other form of non-ionizing radiation. But for most non-scientists, it’s easy to assume that all radiation is capable of causing cancer when, in fact, it’s only the most energetic radiation that can do so. Here’s why.
It's about energy
Due to some of the peculiarities of quantum mechanics, it takes a very specific amount of energy to remove an electron from an atom – even just a smidgeon less, and the atom won’t ionize. And most of the energy in the universe – everything less than UV – simply doesn’t pack enough punch to do the trick. Here’s how I think of it: The building I live in has three stories – the roof is about 40 feet off the ground. My arm is strong enough to throw a ball or a small rock onto the roof of our building. By analogy, I can “ionize” our building. My older daughter, though, can’t throw anything nearly that high – try as she might, she can’t get a ball higher than the middle of the second floor. No matter what she does – no matter how many balls she throws or how long she stands there trying to reach the roof – she’s never going to “ionize” the building because she simply cannot add enough energy to the ball to reach the roof.
By the same logic, it’s impossible for radiofrequency radiation (such as what’s emitted by cell phones) to ionize an atom. And since ionization is the first step of causing the sort of DNA damage that might lead to cancer, radiofrequency radiation is no more capable of initiating cancer through the ionization process than my daughter is of tossing a ball onto the roof of my building.
There has been some speculation that radiofrequency radiation might cause cancer by heating the tissues of the body – chemical reactions, after all, progress more rapidly at higher temperatures, and some of the changes to DNA are the result of chemical reactions. The problem is that the temperature changes caused by talking on a cell phone aren’t very great – no more than the temperature changes from being outside on a hot day, sitting in a sauna or hot tub, or a hot Japanese bath, or any other activities we undertake regularly. Suppose elevated temperatures were correlated with cancer induction. In that case, we’d expect to see higher levels of cancer in those cultures that regularly bake or broil themselves (figuratively speaking, of course!)…and we don’t.
Other mechanisms have been suggested, but they seem incapable of causing the chemical changes needed to give rise to cancer. And that’s the thing; unless somebody can demonstrate an actual way for radiofrequency radiation to generate the type of DNA damage that can lead to cancer – at the levels that our cell phones actually emit it – then people are just guessing.
Going back to my earlier analogy, I can suggest that maybe my daughter has a slingshot or a line-throwing gun or asked her fiancée for help, that she might have used a ladder and dropped the ball on the roof, or something else. But unless we can find a slingshot in her room, ladder marks in the yard, an admission from her fiancé, or some other evidence that she resorted to tools or trickery, this is just a guess. Just as suggestions that some unknown mechanism must be capable of letting radiofrequency radiation – what’s emitted by our cells phones – initiate cancer.
Location, location, location
The other thing to consider, too, is that cell phone radiation is similar to other forms of radiation in that it dies off quickly with distance from the phone, and the tissues of the body absorb it. So the amount of energy deposited in a person’s body from a cell phone will be most significant in the skin of the ear (assuming the user is holding it to their head) – even just a few centimeters away, the exposure will be substantially lower. At greater distances – several inches or even a few feet away – the amount of energy deposited in the tissues is so low as to be barely measurable by any but the most sensitive instruments.
Thus far, there has been no credible mechanism suggested by which cell phone radiation can cause chemical changes or genetic damage that can lead to cancer. Moreover, we have been using cell phones for over a generation yet have not seen any compelling studies reporting significant increases in the rates of the cancers we would expect to see – cancers of the head and neck.
In fact, there are very few studies that have measured the actual energy absorption by the tissues in which the cancers developed, and it’s the energy absorption that’s crucial to determining the amount of possible DNA damage that might occur (if a plausible mechanism by which non-ionizing radiation can cause DNA damage is found). Instead, those reporting these studies make broad assumptions about cell phone use, such as assuming that a higher phone bill correlates with higher levels of cell phone use. However, even this neglects to look at how the phone is used – held to the head, used with earbuds or a headset (wired or wireless), on speakerphone, etc.; all of which would affect energy absorption. This is why, whenever I hear of another study that purports to show that cells phones cause cancer, I’m dubious…and why I continue to use my phone. Cell phones emit radiation, just as do my radiator, microwave, light bulbs, and toaster – it’s just not the sort that can cause cancer.
The Series
Part I – Do Cell Phones Cause Cancer
Part II – Radiofrequency Radiation and Cancer
Part III - Experimental Design (or why rats are not people – among other things)