EXPOSURE TO 60 HZ MAGNETIC-FIELDS IN THE ELECTRIC UTILITY WORK-ENVIRONMENT

Research that has attempted to examine the relationship between work e xposures to magnetic fields and health effects has suffered from limit ed exposure information. Power-frequency electric and magnetic (EM) fi eld exposures vary substantially between industries, occupations, and individuals. In this study magnetic field data were collected for a va riety of occupational categories within an electric utility. The sampl ing procedures emphasized craft occupations that were presumed to have higher exposures to magnetic fields. The objectives were to provide b etter exposure information for an ongoing cancer mortality study, exam ine the relationship between different summary measures of magnetic fi eld exposure, and make available descriptive information useful for ex posure reduction and worker education. Principal components analysis ( PCA) and Varimax rotation were used to explore the relationships betwe en the different summary measures among workers and among the subset o f electrical craft occupations. Discriminant analysis was used to asse ss summary measures es of exposure that differentiated occupational gr oups. Measurements for 770 days generated a total of 42378 hours of ma gnetic field data. Eleven summary indices of exposure were calculated for specific occupational groups. These include arithmetic mean, geome tric mean, median, 95th and 99th percentiles, and fraction of measurem ents exceeding .5, 1, 5, 10, and 100 mu T. Electrical craft occupation s had higher work exposures than non-craft occupations. Electricians a nd substation operators had the highest exposures among craft occupati ons. We identified subsets of summary measures that were intercorrelat ed. The first PCA axis included the geometric mean, median, and the fr actions exceeding 0.5 and 1.0 mu T. This set of measures also were bes t at discriminating occupational groups. The relevance of these findin gs may become more important if consistent associations are found betw een particular occupations and disease and particular occupations and magnetic field summary measures. Further research is needed to evaluat e these exposure assessment findings. (C) 1994 Wiley-Liss, Inc.