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

Abstract

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.

Effect of osmotic dehydration on the dielectric properties of carrots and strawberries

“…Free water has a relaxation frequency around 26 GHz at 37°C, whereas for bound water, microwave energy below 5 GHz will be absorbed more readily (Dawkins et al, 1979). Biological materials have large quantities of bound water, hence absorb microwave energy well at 2450 MHz frequency.…”

Microwave based reversible unfolding and refolding of alcohol oxidase protein probed by fluorescence and circular dichroism spectroscopy

“…The MW radiation effect observed here is probably mediated by the water molecules attached to the protein surface. The protein bound water absorbs MW radiation in the range of 1 -15 GHz [31,32] as compared to the free water molecules that absorb at 19 GHz [1]. The MW frequency of 2.45 GHz used in this investigation is thus fall in the range for protein bound water absorption band.…”

Comparative Assessment of Power Absorption in Heads of Adults and Children Exposed to the Radiation of Cellular Phones at 1800 MHz

“…Biological materials having a large amount of bound water might be expected to present higher values of dielectric properties and therefore a relatively higher absorption of electromagnetic power for frequencies below which the free water starts to disperse, i.e. below about 5 GHz (Dawkins et al, 1979). There is strong indirect evidence based on total body water content indicating that the dielectric properties of children do not significantly differ from adults after the first year of life (Anderson, 2003).…”

“…The decrease in the dielectric properties with age may be due to changes in the water content and the organic composition of tissues with age (Dawkins et al, 1979). Even though the corresponding data are not available for human tissues, the implications for the assessment of children exposure seem to be quite interesting.…”