Stability of Wertheimer–Leeper wire codes as a measure of exposure to residential magnetic fields over a 9- to 11-year interval

Abstract

The Wertheimer -Leeper ( W -L ) wire code is a construct used as a surrogate indicator of residential exposure to electromagnetic fields. However, little is known about how changes in electrical distribution systems affect wire code assignment. The wire code was determined for 150 homes in the Seattle, WA, area twice, 9 -11 years apart. For each home, the authors evaluated whether the electrical configuration around the home and the wire code changed between the two time points. The effect of wire code misclassification on observable odds ratios was evaluated, given hypothetical true control distributions and two different dose -response curves. There was an electrical configuration change for 77 ( 51.3% ) homes, which resulted in a wire code change for 29 ( 19.3% ) homes. Eight ( 5.3% ) other homes had a wire code change due to mapping errors or methodological inconsistencies. Misclassification masked the shape of a threshold ( nonlinear ) dose -response curve and changed the slope of a linear dose -response curve. Although the wire code detected less than half of electrical configuration changes, misclassification of exposure over time may change odds ratios and mask possible dose -response relationships.

Potential role of selection bias in the association between childhood leukemia and residential magnetic fields exposure: A population-based assessment

“…Another limitation is the use of wire codes as a surrogate for magnetic fields exposure since this surrogate is known to have limited ability to estimate magnetic field exposure and was used only in North American studies [29]. However, we used wire codes because our aim was to assess the role of selection bias and this approach could be applied to any known address without requiring active participation or property access.…”

The Epidemiology of Paediatric Brain Cancer — Descriptive Epidemiology and Risk Factors

“…In one clever paper in which the pros and cons of the association between EMFs and childhood brain cancer were debated by two teams, each composed of eight international experts, using 12 pre-determined questions, arguments on both sides ultimately concluded that further research is necessary, an opinion vigorously championed by Carpenter in his paper Electromagnetic fields and cancer: the cost of doing nothing [10]. However, contributing to the confusion regarding EMF exposure are a number of methodological issues pertaining to the measurement of EMF, both in and around residences and in the workplace, issues that have sparked almost as much debate and research as the question of EMF exposure's role in disease [143], [148]- [154]. Such issues include questions about the accuracy of EMF measurements, how to avoid bias in subject selection, where best to measure EMF exposure (e.g., a child's bedroom versus elsewhere in or around the home), how to deal international variations in wiring techniques, how to interpret changes in electrical wiring over time and their effects, and how to adjust for the myriad of other potential confounders like other household exposures and exposures, EMF and otherwise, outside of the home.…”