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Med. Pr. 2012;63(3):317-328

MEASURES OF OCCUPATIONAL EXPOSURE TO TIME-VARYING LOW FREQUENCY MAGNETIC FIELDS OF NON-UNIFORM SPATIAL DISTRIBUTION IN THE LIGHT OF INTERNATIONAL GUIDELINES AND ELECTRODYNAMIC EXPOSURE EFFECTS IN THE HUMAN BODY

MIARY NARAŻENIA ZAWODOWEGO

Jolanta Karpowicz Patryk Zradziński Krzysztof Gryz Central Institute for Labour Protection - National Research Institute, Warszawa, Poland Electromagnetic Hazards Laboratory

Abstract

Introduction: The aim of study was to analyze by computer simulations the electrodynamic effects of magnetic field (MF) on workers, to harmonize the principles of occupational hazards assessment with international guidelines. Material and Methods: Simulations involved 50 Hz MF of various spatial distributions, representing workers' exposure in enterprises. Homogeneous models of σ = 0.2 S/m conductivity and dimensions of body parts - palm, head and trunk - were located at 50 cm ("hand-distance") or 5 cm (adjacent) from the source (circle conductor of 20 cm or 200 cm in diameter). Parameters of magnetic flux density (Bi) affecting the models were the exposure measures, and the induced electric field strength (Ein) was the measure of MF exposure effects. Results: The ratio Ein/Bi in the analyzed cases ranged from 2.59 to 479 (V/m)/T. The strongest correlation (p < 0.001) between Bi and Ein was found for parameters characterizing MF at the surface of body models. Parameters characterizing the averaged value of the field affecting models (measures of non-uniform field exposure following ICNIRP guidelines), were less correlated with exposure effects (p < 0.005). Ein(trunk)/Ein (palm) estimated from Ein calculations was 3.81-4.56 but estimated from parameters representing Bi measurement accounted for 3.96-9.74. Conclusions: It is justified to accept 3.96-9.74 times higher exposure to limb than that to trunk. This supports the regulation of labor law in Poland, which provides that the ceiling value for limb exposure to MF below 800 kHz is fivefold higher than that of the trunk. High uncertainty in assessing the effects of non-uniform fields exposure, resulting from a strong dependence of the Ein/Bi ratio on the conditions of exposure and its applied measures, requires special caution when defining the permissible MF levels and the principles of exposure assessment at workplace. Med Pr 2012;63(3):317-328

Key words

electromagnetic fields, occupational safety and health, exposure measures, exposure effects, numerical modeling