EXPOSURE TO 60-HZ MAGNETIC AND ELECTRIC-FIELDS AT A CANADIAN ELECTRICUTILITY

Objectives The purpose of this study was to estimate exposure to extre mely low frequency (ELF) magnetic and electric fields in the Quebec el ectrical utility Hydro-Quebec. Methods Personal exposures to ELF magne tic and electric fields were measured for workers randomly selected fr om 32 job categories at Hydro-Quebec. Weekly arithmetic and geometric means, and other indices of exposure were estimated from 465 worker-we eks of data. Results By job category, the arithmetic means of the ELF magnetic field exposures ranged from 0.09 to 2.36 mu T. Those of the E LF electric field exposures ranged from 2.5 to 400 V . m(-1). Within e ach field, correlations of either the arithmetic or geometric means wi th alternative indices, including an index of the time rate of change, were generally high (r greater than or equal to 0.8). Exceptions were the 20th percentile of the electric means and the proportion of time above 12.4 and 100 mu T. The day-to-day variation of exposure was grea ter than the variation between workers. The median between-day and bet ween-worker components of variance (as geometric standard deviations) by job category were 2.13 and 1.71 for magnetic fields (2.24 and 1.81 for electric fields). Conclusions Substation workers, hydroelectric ge nerating station operators, and cable splicers showed the highest arit hmetic means for 60-Hz magnetic fields above 1 mu T. For 60-Hz electri c fields, forestry workers, equipment electricians in 735 kV substatio ns, and distribution linemen (contact method) had arithmetic mean expo sures greater than 100 W . m(-1). Of the total variance in the logarit hms of the weekly magnetic and electric field means, job category expl ained 49.6% and 59.5%, respectively.