Ambient 60‐Hz magnetic flux density in an urban neighborhood

A residential neighborhood in Buffalo, NY, was surveyed with a magnetic field meter to evaluate whether or not spot measurements are reliable predictors of the 60‐Hz fields at street corners and residences. The results of repeated measurements over 7 days at 33 street corners in this neighborhood indicate that day‐to‐day variation in power line magnetic fields is negligible (intraclass correlation coefficient = 0.94). Multivariate linear regression analysis of the data indicates that transmission lines and thick, three‐phase primary wires near the field measurement site are strong predictors and account for the majority of the ambient magnetic field variance between locations (multiple correlation coefficient squared = 0.60; F ratio = 22.2, P < .001). Magnetic fields measured at the front sidewalk were highly correlated with fields at the front doorsteps of 45 homes in this neighborhood (γ = 0.81). These results suggest that ambient power line magnetic field levels at urban residences can be reliably characterized on a one‐time site inspection using a hand‐held magnetic field meter and a simple wiring classification system.