BPA Study of Occupational Exposure to 60-HZ Electric Fields

This paper describes the results of a study started in 1979 by the Bonneville Power Administration (BPA) to quantify occupational exposures to 60 Hz electric fields. A miniaturized electric field exposure monitor (EFEM) was developed. To relate the electric field at the surface of the body measured by the EFEM to the unperturbed field, the concept of enhancement factor (EF) is introduced. The EF is the ratio of the measured field at the surface of the body to the unperturbed field. The EF varies with EFEM location, body position, body orientation, and other factors. Laboratory tests were conducted to obtain EF´s for locations of the EFEM. Using 29 EFEMI´s, exposure data have been collected for approximately 2,500 days from 241 workers. Results of the study give estimates of electric field exposure in terms of duration, electric field time histograms, and accumulated daily exposure in (kV/m)h. Exposures are analyzed as a function of voltage level and job category.