Interactive effects in 60-Hz electric-field exposure systems.

The level of exposure of laboratory animals to 60-Hz electric fields is commonly specified in terms of the unperturbed field strength present before the introduction of experimental subjects and their cages. In the research reported in this paper, rats were housed in two parallel rows in 12.4 cm x 25.1 cm x 10.2 cm high plastic cages resting on the lower electrode of a parallel-plate exposure system, and the actual perturbed electric fields experienced by an experimental animal were investigated. The most important results are: 1) Reducing the spacing between the exposure electrodes from 8.7 to 1.7 times the height of a singly exposed rat model, while maintaining a constant unperturbed field strength, resulted in a 15% increase in the electric field at the highest point on the surface of the body and a 10% increase in the short-circuit current of the model. 2) For multiple animal exposures, increases of 10% in both the field at the highest point of the body and the short-circuit current were observed when the electrode spacing was reduced from 8.7 to 2.6 times the height of a rat. 3) Plastic cages caused 1--6% reductions in the electric field at the surface of the body, except very near the cage walls, where enhancements of more than 20% were observed. 4) When 16 rats were simultaneously exposed, the short-circuit current, IS, of an individual subject of weight W (in g), that was surrounded on all sides by other rats of weight W, was reduced from the short-circuit current, IU, measurement with the same subject individually exposed as follows: during a 12 h light (sleeping) cycle, IS/IU = 1.00 -- 0.0173W 1/2; during a 12 h night (awake) cycle, IS/IU = 1.00 -- 0.0136W 1/2.