A few comments here have discussed microwaves influencing biochemistry by non-ionizing mechanisms. To address these concerns, it’s easy to show that microwaves cannot provide enough energy to alter any biochemical pathway unless one imagines a very specific molecular system to absorb energy at this wavelength; similar to chlorophyll absorbing visible light in photosynthesis.

Given the complexity of chlorophyll and its significant support system in photosynthesis, I would highly doubt such a similarly complex molecular system would evade discovery. Further, due to the weak energy of microwaves, as quantified next, such a microwave harvesting system would have to be located at the surface of our skin (or other periphery tissue like hair) to absorb this energy before other biomolecules absorb it non-specifically. I believe these relatively simple periphery tissues have been exhaustively studied.

As the article mentions, microwave energy is on the order of 0.001 kJ/mole. Just to put that in perspective, the random thermal (kinetic) energy contained in each degree of freedom of a biochemical systems is on the order of 2.5 kJ/mole. Due to their weak energy, microwaves have only been shown to non-trivially interact with molecular systems in the gas phase, where collisions between molecules are suppressed, as each molecular collision occurs with enough energy (thermal energy) to overwhelm the much weaker microwave interactions. In the fluid tissues of the body this energy would only be non-specifically absorbed causing a trivial and temporary rise in temperature (1e-4 deg C) within the tissue.

Therefore, I highly doubt microwaves interact with human biochemistry in any interesting or pathology-relevant way.