I wouldn't think that to be a reasonable general assumption. The heating effects could include: changes to reaction kinetics and equilibria; unfolding and de

I wouldn't think that to be a reasonable general assumption. The heating effects could include: changes to reaction kinetics and equilibria; unfolding and denaturing of proteins; unwinding of DNA and RNA in localised regions ("bubbles"); displacement of inter- and intra-molecular associations through hydrogen bonding and van der Waals forces As an example, the unfolding or denaturing of a protein may be transient or permanent, and it will often not have an obvious adverse effect. But if it's e.g. a critical regulatory protein, it may result in a cascade of events which might end up causing cancer. DNA structure is tightly-controlled and is wound up to varying degrees to enable or prevent access to it. If it's transiently unwound by localised heating, it exposes it to the transcription machinery as well as other regulatory proteins. Again, it could have wide-ranging effects. The probability of any one photon doing damage is low, but it penetrates deep and the heating would be very localised. The cumulative effect of exposure could well cause significant problems. Biological systems are very complex, and many of the interactions do not involve bond breaking. The proteins and other molecules interacting within each cell exist in a delicate balance which often involves far weaker forces, including hydrogen bonding and van der Waals forces. These are easily disturbed by heating.