Je. Deadman et al., TASK-BASED ESTIMATION OF PAST EXPOSURES TO 60-HERTZ MAGNETIC AND ELECTRIC-FIELDS AT AN ELECTRICAL UTILITY, Scandinavian journal of work, environment & health, 23(6), 1997, pp. 440-449
Objectives Past exposures of electric utility workers to extremely low
-frequency (ELF) magnetic (B) and electric fields (E) in Quebec were e
stimated. Methods The current intensities were measured and durations
of exposures determined for tasks or work locations in 14 job categori
es. Past task or location intensities were extrapolated from the prese
nt on the basis of interviews with long-term workers and utility perso
nnel. Past task or location durations were estimated for the long-term
workers. Time-weighted average (TWA) exposures for past periods were
reconstructed for jobs from the intensity and duration estimates. Resu
lts Magnetic fields were estimated to have increased the most over tim
e for substation and distribution-line jobs. Magnetic field exposures
for jobs in the generation and transmission of electricity were estima
ted to have increased very little. For substation jobs, the ratios of
magnetic fields in 1945 to those in 1990 ranged from 0.42 to 0.69; the
corresponding figures for distribution-line jobs ranged from 0.36 to
0.94. For electric fields in substations, the estimated increase over
time was less than for magnetic fields, the 1945:1990 ratios ranging f
rom 0.59 to 0.88. For the distribution line jobs, the 1945:1990 ratios
for electric fields were less than 1.0 in 4 cases (0.6 to 0.89), more
than 1.0 in 3 others (1.13 to 2.01) and unchanged in 1. Conclusions R
econstruction of TWA exposures allowed changes in the intensity and th
e duration of exposures to be considered separately. Documentation of
the intensity and duration of exposures for different tasks allows exp
osure reconstruction for jobs that have ceased to exist. The method is
applicable elsewhere if exposure-monitoring records allow the level a
nd duration of exposures for tasks or locations to be calculated and i
f estimates of past durations and intensities of exposures can be reli
ably obtained.