Microwave-induced cataracts: pulsed vs continuous wave irradiation

Damage to rat lenses in vitro caused by continuous (CW) and 24 kWpk microwave pulsed (PW) wave radiation fits a model correlating damage to specific absorption (SA), a product of the specific absorption rate (SAR) and exposure time. This model was extended to include new exposure conditions: higher peak powers of PW radiation at additional pulse durations. The overall model related damage to the SA/dose of radiation. Increasing damage occurred at low doses as the pulse duration increased from 2 to 20 μsec or the peak power of the pulses increased from 24 to 600 kWpk. The enhancement relative to CW irradiation was about 80 times greater at the lowest dose tested when 20 μsec pulses of 600 kWpk microwaves were used. At a 10 μm deep layer of damage in the periphery of the lens, the SAR values for damage were significantly below currently accepted SAR values for the American National Standard Institute (ANSI) safety standard. Consistent with increased damage, experiments using a virtual cathode transmitter delivering 100-200 MW peak power pulses of similar total energy per pulse showed damage after only 10 pulses. The relative biological effect is analogous to that of heavy ion bombardment of the eye lens in experimental cataracts. This new data suggest the need for further exploration into the possibility and the mechanism of accumulative damage from chronic exposure to pulsed microwaves.