VARIABILITY AND CONSISTENCY OF ELECTRIC AND MAGNETIC-FIELD OCCUPATIONAL EXPOSURE MEASUREMENTS

There is widespread scientific and public interest in possible health effects from exposure to electric and magnetic fields at frequencies a ssociated with electricity use. Electric and magnetic field exposure a ssessment presents specific problems, among which are the inherent var iability in exposure, the lack of robust statistical summary measures, and the lack of an accepted metric based on biological response. Thes e pose challenges in defining distinct exposure groups, a basic goal f or exposure assessments used in epidemiological studies. This paper ex plores the extent to which distinct electric and magnetic field exposu re groups can be defined, by examining the variability and consistency of occupational electric and magnetic field exposure measurements amo ng studies and within individual studies. Principal analyses are made by job titles because they are the most frequently used descriptors fo r stratifying occupational exposures to electric and magnetic fields. Methodological issues affecting the degree of consistency in measured electric and magnetic field exposures among occupational environments are also examined. Exposures by job title reported from electric and m agnetic field measurement studies are summarized by general job catego ry and industry. Analyses are performed both within and between job ca tegories. Distributions of daily measured exposures for job categories taken from three large studies in the U.S. electric utility industry are compared to investigate consistency of exposures at a more detaile d level. Analyses of reported personal exposure measurements from many studies and countries are consistent with less rigorous observations made heretofore on the basis of individual studies. In these studies, significantly elevated electric and magnetic field exposures are found in the electrician, lineworker; and substation worker categories; sig nificantly elevated magnetic field exposures are also noted in the gen eration worker category; and magnetic field exposures in these groups are consistent across countries. Analyses within and among the elevate d exposure job categories indicate that there are no significant diffe rences between them. Among the studies, it is not possible to distingu ish between exposures for well-defined groups within the categories, s uch as between transmission lineworkers and distribution lineworkers i n the lineworker category between generation operators and generation mechanics; or between substation operators and substation maintenance workers. This information provides a context for past studies and will help future efforts to define distinct occupational exposure groups e xposed to elecric and magnetic fields. Compilations of measured person al exposure data by industry and job title have been prepared as appen dices (available from the author upon request).