Electric Utility Workers Research Articles

Exposure to power-frequency electromagnetic fields in Denmark.

The purpose of the study was to assess exposure to power-frequency electromagnetic fields in various groups with normal or high exposure in occupational and residential environments. Exposure to power-frequency (50 Hz) electric and magnetic fields was measured for 301 volunteers (396 measurements) in periods of 24 h in both occupational and residential environments. The study included electrical utility workers (generation, transmission, distribution, substation), office and industrial workers, and people living near high-power transmission lines. Electric and magnetic fields were measured with personal dosemeters, and the mean values were calculated for work and nonwork periods. The work-period magnetic field exposure, as the geometric mean of the distribution of the work-period means, for a group of selected industrial workers with high exposure was 6 [geometric standard deviation (GSD) 4.6] muT. The exposure level was 0.10 (GSD 2.4) muT for "normal" industrial workers and 0.09 (GSD 1.8) muT for office workers. For electrical utility workers the corresponding values were 0.72 (GSD 2.5) muT for substation workers, 0.52 (GSD 4.2) muT for generation workers, 0.36 (GSD 3.5) muT for transmission workers, and 0.15 (GSD 2.9) muT for distribution workers. The magnetic field exposure in normal residences was 0.04 (GSD 2.1) muT, and in residences near high-power lines it was 0.29 (GSD 2.8)muT. Corresponding results on exposure to electric fields are given in the study. All of the measurements of exposure to electric and magnetic fields were below the values normally used as guidelines.

Cancer Risks Associated with Occupational Exposure to Magnetic Fields among Electric Utility Workers in Ontario and Quebec, Canada, and France: 1970–1989

To determine whether occupational exposure to magnetic fields of 50-60 Hz was associated with cancer among electric utility workers, the authors used a case-control design nested within three cohorts of workers at electric utilities: Electricité de France--Gaz de France, 170,000 men; Ontario Hydro, 31,543 men; and Hydro-Québec, 21,749 men. During the observation period, 1970-1989, 4,151 new cases of cancer occurred. Each participant's cumulative exposure to magnetic fields was estimated based on measurements of current exposure of 2,066 workers performing tasks similar to those in the cohorts using personal dosimetry. Estimates were also made of past exposure based on knowledge of current loading, work practices, and usage. Workers who had more than the median cumulative exposure to magnetic fields (3.1 microtesla (microT)-years) had a higher risk for acute nonlymphoid leukemia (odds ratio (OR) = 2.41, 95% confidence interval (CI) 1.07-5.44). The same observation holds for acute myeloid leukemia (OR = 3.15, 95% CI 1.20-8.27). There was also an elevated risk for mean exposure above 0.2 microT (acute nonlymphoid leukemia, OR = 2.36, 95% CI 1.00-5.58; acute myeloid leukemia, OR = 2.25, 95% CI 0.79-6.46). However, there were no clear dose-response trends with increasing exposure and no consistency among the three utilities. Men whose cumulative exposure to magnetic fields was above the 90th percentile (15.7 microT-years) had an elevated risk for brain cancer (OR = 1.95, 95% CI 0.76-5.00) that was not statistically significant. No association with magnetic fields was observed for any of the other 29 types of cancer studied, including skin melanoma, male breast cancer, and prostate cancer. Controlling for potential confounding factors did not change the results.

Correlations among indices of electric and magnetic field exposure in electric utility workers

Power-frequency electric and magnetic fields are known to exhibit marked temporal variation, yet in the absence of clear biological indications, the most appropriate summary indices for use in epidemiologic studies are unknown. In order to assess the statistical patterns among candidate indices, data on 4383 worker-days for magnetic fields and 2082 worker-days for electric fields collected for the Electric and Magnetic Field Project for Electric Utilities using the EMDEX meter [Bracken (1990): Palo Alto, CA: Electric Power Research Institute] were analyzed. We examined correlations at the individual and job title group levels among indices of exposure to both electric and magnetic fields, including the arithmetic mean, geometric mean, median, 20th and 90th percentiles, time above lower cutoffs of 20 V/m and 0.2 microT, and time above higher cutoffs of 100 V/m and 2.0 microT. For both electric and magnetic fields, the arithmetic mean was highly correlated with the 90th percentile; moderately correlated with the geometric mean, median, and lower and higher cutoff scores; and weakly correlated with the 20th percentile. Electric and magnetic field indices were generally weakly correlated with one another. Rank-order correlation coefficients were consistently greater than product-moment correlation coefficients. Job title group summary scores showed higher correlations among electric field indices and magnetic field indices and between electric and magnetic field indices than was found for individual worker-days, with only the 20th percentile clearly independent of the others. These results suggest that individuals' exposures are adequately characterized by a measure of central tendency for electric and magnetic fields, such as the arithmetic or geometric mean, and an indicator of a lower threshold or cutoff for each field type, such as the 20th percentile or proportion of time above 20 V/m or 0.2 microT. A single measure of central tendency for each type of field appears to be adequate when exposures are assessed at the job title level.

Cohort and nested case-control studies of hematopoietic cancers and brain cancer among electric utility workers.

Recent studies have raised concern about the potential health effects of occupational exposures to power frequency electric and magnetic fields. We evaluated cancer mortality for leukemia, brain cancer, and lymphoma from 1960 to 1988 in a cohort of 36,221 electric utility workers using cohort analyses and three nested case-control studies. From a volunteer sample of the current workforce that represented a variety of different occupations and work locations, we collected 776 days of magnetic field measurements. We derived exposure information from company job history information and developed exposure scores by linking job history data to measured magnetic fields. In job title analyses, we compared "electrical workers" with other field and craft occupations, office, and technical support staff. Age-specific cancer rates for electrical and reference workers were similar. "Electrical workers" had rate ratios or odds ratios ranging from 0.7 to 1.4. Most ratios were close to 1.0. Lymphomas were slightly elevated compared with leukemias and brain cancers (ratios of 0.9-1.4 vs 0.7-1.2, respectively). Odds ratios for magnetic field exposure indices, based on scores for the mean, median, 99th percentile, and fractions exceeding 10 milligauss and 50 milligauss, were all close to or less than 1.0. The interval estimates indicate no strong association but are somewhat limited by imprecision.

Suicide among electric utility workers in England and Wales.

Suicide among electric utility workers in England and Wales.

Occupational and residential 60-Hz electromagnetic fields and high-frequency electric transients: exposure assessment using a new dosimeter.

One problem that has limited past epidemiologic studies of cancer and exposure to extremely low-frequency (0-100 Hz) electric and magnetic fields has been the lack of adequate methods for assessing personal exposure to these fields. A new 60-Hz electromagnetic field dosimeter was tested to assess occupational and residential exposures of a group of electrical utility workers and a comparison background group over a 7-day period. Comparing work periods only, utility workers' exposures were significantly higher than background levels by a factor of about 10 for electric (E) and magnetic (B) fields and by a factor of 171 for high-frequency transient electric (HFTE) fields. When overall weekly time-weighted averages combining work and nonwork exposures were compared, ratios of the exposed to background groups were lower. B and HFTE exposure ratios remained statistically significant, with values of 3.5 and 58, respectively, whereas the electric field exposure ratio was no longer significant, with a value of 1.7. E-field exposures of the background group were the highest during the nonwork period, probably reflecting the use of electrical appliances at home. Residential E- and B-field exposures were in the same range as published results from other surveys, whereas occupational E-field exposures tended to be lower than exposures reported in other studies. The high variability associated with occupational exposures probably accounts for the latter discrepancy. Worker acceptance of wearing the dosimeter was good: 95% of participants found it to be of little or no inconvenience while at work. At home, 37% found the device to be inconvenient in its present form but would not object to wearing a slightly smaller and lighter dosimeter.