The role of water in microwave absorption by biological material with particular reference to microwave hazards

The problem of the absorption of the energy of plane electromagnetic radiation by an aqueous solution of macromolecules is considered. A simplified model for the hydrated molecule is employed, consisting of a spherical shell of bound water surrounding a spherical core. The power deposition per unit volume of the shell is calculated in the frequency range 100 MHz-100 GHz for several bound water relaxation frequencies. In each case the corresponding values are also calculated for free water for comparison. The values obtained for the bound water are shown to be significantly higher than those for the free water up to frequencies of at least 1 GHz. The maximum difference between these two sets of values is of the order of a factor of five and occurs roughly at the bound water relaxation frequency. Because of the strong coupling between the bound water molecules and the macromolecules present in biological material this result could be a significant factor in the explanation of the biological effects of microwaves at a molecular level.