Every now and then there is an Internet meme pointing to health risks from cell phone usage. According to these, carrying an active phone close to your body, or holding the phone to your head while conversing, have some association with cancer, or possibly other physical health risks. Of course the psychological health risks of excessive smart phone usage are well known and discussed, but here I am just concerned with physiological risks to human health. These internet stories were bolstered in 2011 by official reports that additional studies had found possible links between prolonged cell phone usage and certain cancers in humans.
Various professional bodies have done numerous investigations over the decades about this. In particular, the IEEE has looked into it often, since they are closely associated with wireless phone systems, standards, hardware, networks, software, and so on. Most of their studies found no statistically meaningful health effects, although some studies were statistically "inconclusive", and the above mentioned study found "there could be some risk" to humans. The rationale usually offered for minimal risk is that the microwaves used in cell phone networks are "non-ionizing radiation" so cannot break chemical bonds in your body. Without breaking bonds, DNA mutations are impossible, your genes are safe, and so cancers cannot be triggered.
The other potential cell-damage mechanism usually mentioned is that microwaves can heat biological material (like your body), as in a microwave oven. But the microwave power levels used in cell phones (milliwatts) are far too low to cause detectable heating in nearby tissues. With those two potential mechanisms out of the way, it is happily concluded that, aside from that troubling study, there is little risk that cell phone signals can cause cancer or other diseases.
While it is true that microwaves are non-ionizing, the accompanying argument that only thermal effects are important may be too simplistic. Biological molecules may, conceivably, also react to microwaves in additional ways in some cases. Depending on the size, shape and electron charge distribution in the molecules, they may react to microwaves by twisting, vibrating, or rotating (spinning). That is what happens to water molecules in a microwave oven, after all, leading to the desired heating effect. If certain biological molecules happen to resonate with wireless frequencies (which vary over a wide range, from 500 to 5000 MHz or so), then perhaps their response could, in principle, prevent (or speed up) their biological function or behaviour.
Biological molecules have complex behaviours: connecting to or releasing another molecule, being bent, shaped or reshaped inside a cell, passing through cell wall portals, holding two other molecules close together, and so on. If any of these actions is disrupted, sped up, or slowed down in some way, that in turn could interfere with its normal operation inside or between cells. Given the complexity of biochemical reactions, it is probably impossible to say there cannot be any such effect at all. In the worst case, if DNA replication were tweaked even a little, say by increasing the vibrational noise level around the process at some frequency, then copying errors (mutations) might be slightly more frequent. It may therefore, be impossible to rule out an occasional cancer getting a foothold, just at a very low statistical level. Alternatively, if the microwaves disrupt a pore in the cell membrane, it could affect the cell's uptake or discharge of chemicals, such as carcinogens from the cellular environment, or internal wastes. In that case, the microwaves themselves would not "cause" the cancer, but could make the cell more susceptible to cancers caused by those substances.
I do not want to raise fears of cell phones or microwaves in general, and I certainly do not want to start another Internet meme to that effect! However, I have never seen this potential mechanism addressed, much less refuted in what I have read on this subject -- admittedly a small sampling of the available literature. It would be interesting to see what the experts have to say about this. Perhaps they have already examined this possibility and dismissed it? Maybe the microwave frequencies are all wrong for affecting biochemicals? Maybe the resulting vibration or rotational effects are orders of magnitude below the noise level in the cell? I don't know, but it seems that no potential mechanism should be ignored just because it is complicated or difficult to assess.
I note in closing that the same articles reporting negligible health risks of cell phone usage usually also advise that users practice "pragmatic measures" or "prudent precautions" to reduce the (supposedly negligible) risks of microwave exposure. Perhaps after the 2011 reports they are hedging their bets and may now be open to considering the above potential mechanism? Nevertheless, please don't worry about your phone based on my speculations, and do not spread rumours. I am certainly not going to stop using my phone, although I don't often carry it on my person. In any case, there are enough real health hazards in our world to worry excessively about potential ones.
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