BENER Abstract No. 15163. MORTALITY OF PERSONNEL OPERATING ELECTRIC POWER SUBSTATIONS WITH 500 KV VOLTAGE.
(Rus.) Gurvich, E. B.; Novokhatskaia, E. A.; Rubtsova, N. B. [Inst. of Labor Medicine, Russian Acad. of Medical Sciences, Moscow, Russia] Med Tr Prom Ekol (10):18-21; 1995 (15 Refs).
The authors performed a retrospective cohort study of mortality levels in service personnel working on 500 kV, 50 Hz electricity transmission lines. These personnel performed various services at power distribution stations, including repairs, preventive maintenance, control of relays, insulation, thunderstorm protection devices, etc. For these workers, the industrial frequency electromagnetic field (IF EMF) was the most significant potentially unfavorable occupational factor. The levels of magnetic and electric fields were measured at various work places at heights of 1.8, 1.5, and 0.5 m from the ground; a total of over 20,000 measurements were performed. The duration of being under certain field conditions was assessed by chronometry of respective professional services. The electric field levels ranged from 0 to 28 kV/m; the workers spent 58% to 86% of their time under 6- to 25-kV/m fields. The measured levels of the magnetic field (from 0.16-10.8 A/m; approximately 2-136 mG) were far below the legal safety limits (1,400 A/m (approximately 17.6 G) for 8 hr/day), but still exceeded the natural background by 1-2 orders of magnitude. After studying about 10,000 archive documents for 6 power distribution stations (all situated in the central part of Russia), the authors identified 1532 people who worked there for at least 1 yr between 1956 and 1992 and were suitable for the group. Out of them, 141 people had died, and no data could be found for other 72 (5.5%), leaving 1460 in the analysis. For data analysis, the authors used a method of calculation of "human-years," which for the 37-yr period of analysis yielded to 19,272 human-years for men and 4,519 human-years for women. The control for the data was the average mortality in the population of the same regions. The effect of IF EMF was quantitatively assessed by a standardized risk factor (SRF), with necessary consideration of sex and gender differences. The percentage of causes of deaths in male personnel was found to be the same as in the control population: 32.3% died from cardiovascular diseases, 30.1% died from malignancies, 24.8% were from accidents, traumas, and poisonings. SRF for all deaths together equaled 0.61, what is known in epidemiology as a healthy worker effect (SRF of less than 1 means lower mortality than in the control population). SRF levels for cardiovascular diseases, malignancies, and traumas + accidents + poisonings were 0.54, 0.89, and 0.95, respectively. SRF values were about the same for different specialties within the cohort, and even for the most exposed ones they did not exceed the control. The only cause of death which yielded a SRF over 1 was leukemia, which caused 2 deaths instead of 0.99 expected (SRF = 2.03 (confidence interval of 0.23-7.31). Of course, this result was not statistically significant. Although the study did not reveal any effect of the occupational IF EMF exposure on the mortality, the authors consider that possible induction of leukemia deserves additional study in a larger cohort.
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