Residential magnetic fields predicted from wiring configurations: I. Exposure model.
A physically based model for residential magnetic fields from electric transmission and distribution wiring was developed to reanalyze the Los Angeles study of childhood leukemia by London et al. For this exposure model, magnetic field measurements were fitted to a function of wire configuration attributes that was derived from a multipole expansion of the Law of Biot and Savart. The model parameters were determined by nonlinear regression techniques, using wiring data, distances, and the geometric mean of the ELF magnetic field magnitude from 24-h bedroom measurements taken at 288 homes during the epidemiologic study. The best fit to the measurement data was obtained with separate models for the two major utilities serving Los Angeles County. This model's predictions produced a correlation of 0.40 with the measured fields, an improvement on the 0.27 correlation obtained with the Wertheimer-Leeper (WL) wire code. For the leukemia risk analysis in a companion paper, the regression model predicts exposures to the 24-h geometric mean of the ELF magnetic fields in Los Angeles homes where only wiring data and distances have been obtained. Since these input parameters for the exposure model usually do not change for many years, the predicted magnetic fields will be stable over long time periods, just like the WL code. If the geometric mean is not the exposure metric associated with cancer, this regression technique could be used to estimate long-term exposures to temporal variability metrics and other characteristics of the ELF magnetic field which may be cancer risk factors.
Bowman
J D
JD
National Institute for Occupational Safety and Health, Cincinnati, Ohio 45266, USA. jdb0@cdc.gov
Thomas
D C
DC
Jiang
L
L
Jiang
F
F
Peters
J M
JM
D000465:Algorithms; D002648:Child; D004560:Electricity; D004574:Electromagnetic Fields / Q000009:adverse effects; D004781:Environmental Exposure; D005544:Forecasting; D006798:Housing; D006801:Humans; D007953:Leukemia, Radiation-Induced / Q000453:epidemiology; D015141:Los Angeles / Q000453:epidemiology; D008280:Magnetics / Q000009:adverse effects; D008954:Models, Biological; D017711:Nonlinear Dynamics; D011210:Power Plants; D012044:Regression Analysis; D012307:Risk Factors