title: [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].
abstract: BACKGROUND
  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.
  
  
  METHODS
  Simulations involved 50 Hz MF of various spatial distributions, representing workers' exposure in enterprises. Homogeneous models of sigma = 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 (B(i)) affecting the models were the exposure measures, and the induced electric field strength (E(in)) was the measure of MF exposure effects.
  
  
  RESULTS
  The ratio E(in)/B(i) in the analyzed cases ranged from 2.59 to 479 (V/m)/T. The strongest correlation (p < 0.001) between B(i) and E(in) 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). E(in)(trunk)/E(in) (palm) estimated from E(in) calculations was 3.81-4.56 but estimated from parameters representing B(i) 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 E(in)/B(i) 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.
authors.affiliation: Electromagnetic Hazards Laboratory, Central Institute for Labour Protection - National Research Institute, Warszawa, Poland. jokar@ciop.pl
authors.forename: Jolanta
authors.initials: J
authors.lastname: Karpowicz
authors.forename: Patryk
authors.initials: P
authors.lastname: Zradziński
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Gryz
mesh_terms: D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D004574:Electromagnetic Fields; D017408:Guidelines as Topic; D006801:Humans; D008452:Maximum Allowable Concentration; D008962:Models, Theoretical; D016273:Occupational Exposure / Q000032:analysis*; D016272:Occupational Health / Q000331:legislation & jurisprudence / Q000592:standards; D011044:Poland