Energy issues in mechanisms

Do EMFs have enough energy to break bonds?

The short answer

Power-frequency fields (at 50 or 60 Hz) do not have enough quantum energy directly to break chemical bonds and therefore they do not have enough quantum energy directly to damage DNA. 

That is undisputed physics, but in itself it does not prove that EMFs can't damage DNA.  There may be other, indirect, mechanisms.  When we look at those indirect mechanisms as well, we still conclude that we haven't identified a mechanism that could plausibly produce biological effects at the level of fields people are exposed to.  But that is a less robust and more subtle argument.  Just saying "EMFs don't have enough energy so they can't damage DNA" is too simple and not the whole picture.

A longer answer

In our main page on the plausibility of biophysical mechanisms, we explain how any effect that a field produces on at atom, molecule or cell must be bigger than the effects produced naturally all the time in biological systems by random thermal vibrations or other "noise".

One particular aspect of this concerns the energy of a field.  One process by which a field could potentially affect a living system is by breaking chemical bonds - by damaging DNA, for instance, or by causing ionisation. 

The direct absorption of energy by a chemical bond is a quantum effect. One quantum of energy is absorbed, and either that is enough or it's not enough to break the bond.  The quantum energy of electromagnetic fields is solely related to the frequency.  So all 50 Hz fields have the same quantum energy, regardless of the strength of the field.  The quantum energy of a 50 Hz field is actually tiny (see below for the actual numbers) and well below the level required to break bonds.  So we can say with confidence that whatever else EMFs may or may not do, they don't directly break chemical bonds or cause ionisation.  That is why they are also described as "non-ionising" radiation.

But of course, direct absorption of energy is not the only way a field might cause bonds to break.  Just two of the other possibilities are that fields might accelerate charged particles or cause them to vibrate sufficiently for bonds to break, or they might change the concentration of something else (e.g. a particular entity called a free radical) which can damage bonds.  Both of these would be dependent on the strength of the field as well as its frequency.

In fact, when we examine these alternative suggestions, we still conclude that no mechanism has yet been identified that can explain how fields of the level people encounter could damage DNA.  But this is not the same thing as saying "it's impossible", because there might be a subtle twist to the way a mechanism operates, or a mechanism we haven't thought of yet.  So we can legitimately say that the absence of a mechanism makes health effects of EMFs less plausible, but we can't say it makes them impossible.

And we can't rule out the possibility that EMFs damage DNA solely on the basis that they don't have enough energy.

The numbers

The quantum energy of electromagnetic radiation is given by Plank's constant times the frequency:

E = h f

Plank's constant h is 6.626068 x 10-34 m2 kg / s.  So the quantum energy of electromagnetic radiation at 50 Hz is

E = 6.6 x 10-34  x 50 = 3.3 x 10-32 J

Because that is such a small number we often express it in electron volts (eV) instead of joules (J)

E = 2.1 x 10-13 eV

The energies required to break even the weakest chemical bonds are of the order of 1 eV for covalent bonds and 0.1 eV for hydrogen bonds.  So the quantum energy of 50 Hz electromagnetic waves is too small to break bonds directly by a factor of 1011.

Note that this "single photon" model of interactions is not really appropriate anyway when the distance scale of cells and molecules is so much less than the wavelength.  But it serves to illustrate the point.

See also: