The Importance of Bound Water Studies in the Determination of Energy Absorption in Biological Tissue

Methods are described for determining the electrical parameters of bound water in biological tissue from dielectric measurements made at radiowave and microwave frequencies. These parameters are then used to calculate at various frequencies the relative energy absorption in the macromolecules, bound water and free water present. It is shown that between 70 - 4000MHz the value of the energy absorbed per unit volume by the bound water is higher, and at the lower frequencies considerably higher, than for the free water. At 2450MHz the ratio of the values is about two. At 4GHz the absorption curves cross over and the effect of the free water becomes dominant at higher frequencies. Since any biological effects of microwaves are presumably due to energy absorption in the macromolecules, which are immediately adjacent to the bound water, it is clear that some frequencies are potentially more hazardous than others.