Effects of microwave radiation on the eye: the occupational health perspective.

The purpose of this overview is to promote an interest in understanding and reducing the possible occupational health risks of microwave radiation on the eye. Microwaves act on living tissue through two types of mechanisms, thermal and nonthermal. Lens opacities can be induced in experimental animals at relatively high intensities (power densities greater than 100 mW/cm2). For lower intensities, lens changes may depend on the cumulative dose. At "nonthermal intensities", microwaves can act as a trigger and set off changes in the living tissues (e.g. Ca++ efflux). Some cataract-causing agents (alloxan and galactose) act synergistically with microwaves. Microwaves also accelerate formation of cataracts due to diabetes. The corneal endothelium can be damaged by microwaves alone or in combination with some drugs. Microwave degeneration of retinal nerve endings and a small increase in retinal permeability were also found in animals. The effect of long-term low-intensity microwave exposure on the human lens remains poorly understood. Several reports have implicated occupational microwave exposure as a factor in increasing the rate of lens aging and retinal injury in microwave workers. In Canada, recommended microwave exposure limits are set at 25 mW/cm2 for microwave workers and at 1 mW/cm2 for the general public (both averaged over 1 minute). The Australian microwave exposure safety standard (1985) recommends pre- and post-employment eye examinations for workers.