Bawin and her coworkers have reported changes in binding of calcium after exposure of avian brain tissue to nonionizing electromagnetic radiation. Because calcium is intimately involved in the electrical activity of the brain, their results reveal a heretofore unrecognized potential for nonionizing radiofrequency radiation to affect biological function. We have verified and extended their findings. The forebrains of newly hatched chickens, separated at the midline to provide treatment-control pairs, were labeled in vitro with radioactive calcium. Samples of tissue were exposed for 20 minutes in a Crawford irradiation chamber to 147-MHz radiation, which was amplitude modulated sinusoidally at selected frequencies between 3 and 30 Hz. Power densities of incident radiation ranged between 0.5 and 2 mW cm -2. Compared with nonirradiated samples, a statistically significant increase in efflux ofcalcium ions (P < 0.01) was observed in irradiated samples at a modulation frequency of 16 Hz and at a power density of 0.75 mW cm -2. Our data confirm the existence of the frequency "window" reported by Bawin et al., as well as a narrow power-density "window" within which efflux of calcium ions is enhanced. 0048-6604/79/1112-S014501.00 93 94 BLACKMAN ET AL.

Radiofrequency (RF) energy has been reported to cause a variety of ocular effects, primarily cataracts but also effects on the retina, cornea, and other ocular systems. Cataracts have been observed in experimental animals when one eye was exposed to a localized, very high RF field and the other eye was the unexposed control. The results show that 2450 MHz exposures for >or=30 min at power densities causing extremely high dose rates (>or=150 W/kg) and temperatures (>or=41 degrees C) in or near the lens caused cataracts in the rabbit eye. However, cataracts were not observed in the monkey eye exposed to similar exposure conditions, reflecting the different patterns of energy absorption (SAR, specific absorption rate) distribution, due to their different facial structure. Since the monkey head is similar in structure to the human head, the nonhuman primate study showed that the incident power density levels causing cataracts in rabbits and other laboratory animals cannot be directly extrapolated to primates, including human beings. It is reasonable to assume that an SAR that would induce temperatures >or=41 degrees C in or near the lens in the human eye would produce cataracts by the same mechanism (heating) that caused cataracts in the rabbit lens; however, such an exposure would greatly exceed the currently allowable limits for human exposure and would be expected to cause unacceptable effects in other parts of the eye and face. Other ocular effects including corneal lesions, retinal effects, and changes in vascular permeability, have been observed after localized exposure of the eye of laboratory animals to both continuous wave (CW) and pulsed wave (PW) exposures, but the inconsistencies in these results, the failure to independently confirm corneal lesions after CW exposure, the failure to independently confirm retinal effects after PW exposure, and the absence of functional changes in vision are reasons why these ocular effects are not useful in defining an adverse effect level for RF exposure. While cataracts develop after localized exposure of the eye at SARs >or= 150 W/kg, whole body exposure at much lower levels (14-42 W/kg) is lethal to rabbits. Two studies reported cataracts in this animal after 30 daily exposures at SARs at the upper end of the lethal range, e.g., 38-42 W/kg; however, long term exposure of rabbits (23 h/day, 6 months) at 1.5 W/kg (17 W/kg in the rabbit head) did not cause cataracts or other ocular effects. A long term (1-4 years) investigation of monkeys exposed at high SARs (20 and 40 W/kg to the monkey face) found no cataracts or other ocular effects or change in visual capability. The results of these long term studies support the conclusion that clinically significant ocular effects, including cataracts, have not been confirmed in human populations exposed for long periods of time to low level RF energy. The results of four recent human studies show that there is no clear evidence of an association between RF exposure and ocular cancer.

Changes have been found in calcium-ion binding to brain tissue exposed in vitro to a specific power density (0.83 mW/cm2) of 147-MHz radiation, amplitude modulated by a 16-Hz sine wave. This report replicates and extends this previous work. To define more precisely the range of effective power densities, two different numbers of samples were treated in a Crawford cell. In one series, four brain tissues were exposed at a time; in the other series, four brain tissues plus six dummy loads were exposed together. While the four-sample configuration produced a narrow power-density window, the ten pseudosample configuration resulted in a broader power-density window. The reason for the sample-number dependence is unresolved, but may be due to interactions between samples and field distortions caused by the close spacing. The ten pseudosample configuration was used to test for the presence and rage of a power-density window at a sinusoidal modulation frequency of 9 Hz. The response curve at 9 Hz was essentially identical to the results for 16-Hz sinewave modulation.

The human auditory response to pulses of radiofrequency (RF) energy, commonly called RF hearing, is a well established phenomenon. RF induced sounds can be characterized as low intensity sounds because, in general, a quiet environment is required for the auditory response. The sound is similar to other common sounds such as a click, buzz, hiss, knock, or chirp. Effective radiofrequencies range from 2.4 to 10 000 MHz, but an individual's ability to hear RF induced sounds is dependent upon high frequency acoustic hearing in the kHz range above about 5 kHz. The site of conversion of RF energy to acoustic energy is within or peripheral to the cochlea, and once the cochlea is stimulated, the detection of RF induced sounds in humans and RF induced auditory responses in animals is similar to acoustic sound detection. The fundamental frequency of RF induced sounds is independent of the frequency of the radiowaves but dependent upon head dimensions. The auditory response has been shown to be dependent upon the energy in a single pulse and not on average power density. The weight of evidence of the results of human, animal, and modeling studies supports the thermoelastic expansion theory as the explanation for the RF hearing phenomenon. RF induced sounds involve the perception via bone conduction of thermally generated sound transients, that is, audible sounds are produced by rapid thermal expansion resulting from a calculated temperature rise of only 5 Â 10 À6 8C in tissue at the threshold level due to absorption of the energy in the RF pulse. The hearing of RF induced sounds at exposure levels many orders of magnitude greater than the hearing threshold is considered to be a biological effect without an accompanying health effect. This conclusion is supported by a comparison of pressure induced in the body by RF pulses to pressure associated with hazardous acoustic energy and clinical ultrasound procedures. Bioelectromagnetics Supplement 6:S162-S173, 2003.

Rat liver mitochondria respiring in a phosphatefree bicarbonate buffer accumulate substantial amounts of Ca2+, to levels suggesting that the bicarbonate buffer is furnishing the required counteranion for Ca2+. When the HC0r-C02 buffer was labeled with 14C, the isotope was accumulated in large amounts. The 4SCa2+: 14C uptake ratio of 1.0 and the finding that the accumulated 14C was completely released as a gaseous product, presumably C02, by exposure of the loaded mitochondria to dilute acid, indicated that CaC03 accumulated in the matrix. Up to about 300 nmol of Ca 2+/mg of protein, the accumulation of carbonate was as rapid as accumulation of phosphate from a phosphate-buffered medium. Carbonate accumulation also occurs when Ca2+ is replaced by Sr24" or Mn2+, but not when the divalent cation is Mg2+. Entry of both Ca2+ and C0 32" is blocked by respiratory inhibitors, uncoupling agents, and by La3+ and ruthenium l3icarbonate is a major intracellular anion, which largely derives from the decarboxylation reactions of the tricarboxylic acid cycle in the mitochondrial matrix. However, relatively little information is available regarding the movement of bicarbonate or C02 through the mitochondrial membrane and its relationship to the transmembrane movements of other anions and cations.In this paper we report the results of one approach to this problem. It is based on the fact that respiration-dependent accumulation of Ca24" in the mitochondrial matrix takes place only if it is accompanied by entry of an electrically equivalent counteranion such as phosphate (Lehninger et al., 1967;Gear et al., 1967;Lehninger, 1972). We have found that a bicarbonate buffer system can replace phosphate as a source of counteranion for the accumulation of Ca2+ by respiring rat liver mitochondria. The entering species has been shown to be dissolved C02, which accumulates in a form tentatively identified as carbonate ion. The accumulation of both carbonate and Ca2+ by the respiring mitochondria is inhibited by Diamox (acetazolamide), an inhibitor of carbonic anhydrase. An abstract of this work has been published (Elder, 1972). Experimental ProcedurePreparation of Mitochondria. Mitochondria were isolated from livers of male Sprague-Dawley albino rats in 220 mM mannitol, 70 mM sucrose, 0.5 mg/ml of bovine serum albumin, and 2 mM potassium Hepes* 1 buffer (pH 7.4), or in 0.25 µ f From the