Misclassification of ELF occupational exposure resulting from spatial variation of the magnetic field

The adequacy of a single hip- or chest-worn magnetic field dosimeter to reliably classify subjects with respect to their occupational ELF magnetic field exposure is investigated. Hip-worn dosimeters consistently underestimate both whole-body average exposure and head exposure, tentatively regarded here as two possible definitions of the "true" exposure measurement. The approximate resulting bias in the relative risk estimate in hypothetical case-control studies is evaluated. A chest-worn dosimeter is found to be generally superior to a hip-worn one in assessing exposure during the occupational tasks considered here.