I.A. Marriott, M.A. Stuchly
Surveys report a high incidence of eye-related complaints among VDU operators, though eyestrain is not recognized as a clinical entity. Reflections from external light sources are the most common and serious factor degrading screen image quality. Adjustable furniture reduces musculoskeletal complaints, but a preferred posture remains undefined. Physical complaints about VDUs are inversely related to job satisfaction.
Unknown authors
Unknown authors
The Department of Health, Education and Welfare reported that implanted pacemaker dysfunction has been observed near electrocautery, radar, communications systems, electric shavers, spark coils, and gasoline ignition systems. The Association for the Advancement of Medical Instrumentation stated that interference signals mimicking a heartbeat can be misinterpreted by pacemakers and change their output. Even microwave ovens complying with leakage limits of 0.0001 mW/cm2 at 5cm may cause electromagnetic interference within a few meters.
Herman Schwan, Kam Li
Leo Birenbaum et al.
Arthur Holly Compton
Kenneth T. S. Yao, Mayme M. Jiles
Researchers grew cells derived from the bone marrow and retinal choroid of the rat kangaroo (Rotrurus tridactylus) and exposed them to 2450 MHz microwave radiation for 5 to 20 minutes at distances of 10, 25, or 50 cm. Short exposure times at the longer distances resulted in cell growth greater than that of unirradiated controls. Longer exposure times at shorter distances impaired cell proliferation. Chromosome damage appeared in cells exposed at 10 cm for at least 10 minutes, and the percentage of damaged cells increased with longer exposure. When cells were sensitized with 5-bromodeoxyuridine, chromosome damage tripled.
Russell L. Carpenter
James M. Wyckoff
Good measurements are the key to safe application of both ionizing and nonionizing radiation in industry, medicine, and consumer products. The National Bureau of Standards is expanding its measurement services to radiation users and collaborates with federal agencies to develop realistic measurement requirements for regulations. The report reviews the state of measurement art for X-ray, nuclide, ultraviolet, laser, electromagnetic, and ultrasonic radiation, highlighting the need for stable and accurate transfer standards.
Stephen F. Cleary
Table I summarizes reported in vivo effects in humans including hyperthermia, cataracts, auditory nerve responses, and neurological effects. Reported effects in experimental animals include mutations, hyperthermia, burns, testicular effects, and chromosomal aberrations. In vitro effects listed include mitotic arrest, resonance absorption in methyl palmitate, pearl-chain formation, and enzyme inactivation.
Unknown authors
Female Sprague-Dawley rats were exposed to 2.45 GHz continuous-wave microwaves at 28 mW/cm² for 100 minutes daily from days 6 to 15 of pregnancy. The study included 67 sham-irradiated and 70 irradiated females, resulting in 64 and 66 pregnancies respectively. No significant differences were found in pregnancy rates, litter size, or the incidence of external, visceral, or skeletal anomalies between the groups. In a separate experiment, 35% of adult rats exposed to 40 mW/cm² died from hyperthermia.
Unknown authors
Researchers exposed Salmonella typhimurium to 2.45 GHz amplitude-modulated microwave radiation at an average specific absorption rate of approximately 2.5 mW/g in a waveguide inside a 37°C incubator. Stationary-phase and log-phase bacteria were exposed for three hours, and stationary-phase bacteria were also exposed for 24 hours. No effect on viability or mutation frequency was seen after three-hour exposure, but one of five strains exposed for 24 hours showed reduced viability and increased mutation frequency compared with a 37°C control, though not compared with a 39°C control. Reconstruction experiments found the vial temperature inside the waveguide was about 1.5°C higher than the incubator temperature, which could explain the observed changes.
Unknown authors
Researchers studied the effect of temperature on isolated rat lenses incubated in tissue culture medium. Lenses maintained clarity in medium 199 with 10% fetal calf serum for up to two weeks, but high glucose caused opacities and globular degeneration within one day. Similar loss of transparency occurred after lenses were warmed to 39°C or 41°C for one hour and then incubated at 37°C for 24 hours. Lenses exposed to 60°C or 65°C for one hour did not become opaque, likely due to fixation.
Unknown authors
Researchers used prolate spheroid and ellipsoidal models to estimate electromagnetic power absorption in adult and infant human heads. A perturbation technique evaluated internal electric fields to estimate time-averaged and space-averaged specific absorbed power. The study compared results with animal experimental data and concluded ellipsoidal models are better than spheroid and sphere types.
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Unknown authors
Five different absorber-lined laboratory test systems were designed and built, and the uncertainty of each test was analyzed. Error values for each parameter were computed for each instrument, and a worst-case composite uncertainty was calculated for each model. Special tests evaluated parasitic interaction of E-field probes with the H-field and impedance loading of meters.
Unknown authors
Research on the biological effects of microwaves is primarily related to the problem of hazard assessment for exposure of man. For the 2-3 GHz range, extrapolation factors for humans are 1:2 for dogs, 1:8 for rhesus monkeys, 2:7 for squirrel monkeys, and 5:2 for rats.
Unknown authors
Eight male hooded rats performed a vigilance task pressing two levers for tones and food pellets during 40-minute sessions in Styrofoam boxes located in the far zone region of a horn in an anechoic chamber. After stable responding, they were exposed to 1.28 GHz microwaves pulsed at 380 pps with 2 µsec pulses at power densities from 0 to 15 mW/cm². At 15 mW/cm² all eight rats showed decreased observing lever response rates, with some ceasing responding, but most adapted by the third exposure. Seven rats decreased response rates at 10 mW/cm² and three showed disruption at 5.5 mW/cm², while other behavioral indices were less sensitive.
Unknown authors
Control samples were processed identically without microwave power applied. The authors concluded that low power density pulsed microwave energy does not significantly alter calcium efflux.
Unknown authors
The study developed a generalized numerical model using the method of moments to compute electromagnetic field distribution and absorbed power in complex-shaped heterogeneous three-dimensional biological bodies. At 2450 MHz, excellent agreement between computed and measured results was obtained for homogeneous and heterogeneous cylinders with various field orientations, and very good agreement was found for rat-shaped models with parallel or orthogonal electric fields.
Unknown authors
The cavity must be mechanically adjustable because its physical dimensions dictate the operating frequency. The prototype cavity cross-section adjusts from 24 by 24 inches down to 6 by 6 inches, and the length adjusts from 4 feet to 1 foot. The cavity is large enough to irradiate mice, cell samples, bacteria, other microorganisms, and phantom scale models. Simultaneous excitation of two cavity modes allows independent control of electric and magnetic field phase and magnitude, enabling selection of virtually any field impedance including plane wave conditions.
Unknown authors
The paper describes a microwave exposure system for three experiments using CW millimeter waves. The system uses a Siemens RWO-60 backward wave oscillator powered by a Micro-Now 702 supply with a 2-hour frequency stability of at least 1 part in 2000 near 50 GHz. A Narda horn with a 1 cm by 1.43 cm aperture is positioned about 2 mm above each biological sample, which is a 1-2.5 mm layer that absorbs nearly all incident power. The instrumentation measures net power leaving the horn and uses a standing wave indicator to keep power constant as samples are changed. The exposure chamber is temperature-stabilized by a water bath, and the horn is heated to match the bath temperature.
Unknown authors
Monolayer cultures of BHK-21/C13 cells were exposed to E-band microwaves at 292 mW/cm2 or U-band at 177 mW/cm2 for 15 minutes, with four cultures per frequency. Protein synthesis was measured by autoradiography of 3H-methionine incorporation across the waveguide axis, providing data at 16 to 25 power densities per band. Results from 100 frequencies between 43–48 GHz and 65–70 GHz showed no significant difference from sham controls and no evidence of a power window.
Unknown authors
After error correction, residual errors were about .1 dB in return loss and 1° in phase. These errors correspond to about 2.5% error in dielectric constant and 12% error in loss tangent for water, and 1.7% and 2.4% for methanol. The probe technique is the only practical approach for in vivo samples but requires multiple measurements for repeatability.
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