90% of the available energy is lost in some form of heat, transferring light energy into different living organisms
The risk of lung cancer death is no different between medium, low, and very low-tar cigarettes.
People who smoke low-tar cigarettes compensate the lack of tar by changing their breathing habits, for example, they will take deeper drags or hold the smoke in for a longer period of time, basically negating the supposed " low-tar" effect.