Results of a multisite study of U.S. residential magnetic fields

Abstract

This paper describes the study design, measurement protocols, and results of a project examining residential magnetic -field exposures at eight sites across the contiguous United States. The goal of the project was to investigate surrogates that have been used in epidemiologic studies to characterize residential magnetic -field exposure. These surrogates include: personal -exposure ( PE ), fixed -location long -term ( LT ), and outside and inside point -in -time ( PIT ) magnetic -field measurements; net -service ( or ground current ) measurements; and the ''wire -code category'' of the residence. ( The latter is a surrogate for magnetic -field exposure based on the nature and proximity of electric power lines outside the house. ) Measurements were conducted on four visits to each of eight sites between January 1994 and June 1997 for a study population of 218 single -unit detached dwellings. Information on the residence, residents, and neighborhood was collected. A simple random sample of 392 single -unit detached dwellings at the sites was used to create a weighted sample of houses representative of the population of single -unit residences. The correlations among the various types of 60 -Hz magnetic -field measures were relatively strong ( Pearson r > 0.74, Spearman > 0.78 ). Variability of PE and LT measurements, as measured by the standard deviations during a visit, was independent of wire -code category. Visit means for PE, LT, and outside and inside PIT were well correlated over periods between visits of from 1.5 to 20 months ( r > 0.62, > 0.76 ). These results support the use of survey measurements ( less demanding than personal monitoring ) to represent exposure that occurred up to 20 months in the past. The principal component of the total variance in PE measurements was the between -house variance; betweenvisit and between -site variances were generally less important. This supports the sampling of many houses with relatively few visits in residential exposure characterization studies. There was a trend for presumably higher wire -code categories to be associated with higher field summary measures for all summary measures related to magnetic -field magnitude, including PE and LT resultant, and inside and outside resultant ( 60 Hz ) and harmonics. However, because of the overlap in field levels between categories, wire code was not a good predictor of magnetic -field levels, accounting for less than 21% of the variance in magnetic -field measurements.

Wire coding in the EMF and Breast Cancer on Long Island Study: relationship to magnetic fields

“…This observation is consistent with results from a study of potential confounders of wire codes in southern Connecticut, which found that VHCC homes were more likely to be built before 1949 (OR ¼ 73.24; 95% CI 29.53-181.65) (Bracken et al, 1998). It is also consistent with a study in eight sites throughout the US, where VHCC homes tended to be older than UG homes (Rankin et al, 2002).…”

Personal Measures of Power-Frequency Magnetic Field Exposure Among Men From an Infertility Clinic: Distribution, Temporal Variability and Correlation With Their Female Partners' Exposure

“…However, if investigators are interested in exposures occurring outside the home only, then more 1 d of sampling would be required to adequately capture the intra-individual variability in exposures that are experienced over time regardless of the selected exposure metric. Others (3,5,7,16,25) have also examined the temporal variability of personal magnetic field exposure metrics in adults and have reported similar findings for the exposure metrics assessed in the present study. Thus, there appears to be consensus across several cohorts that exposure measurement error due to temporal variability is much more problematic for those exposure metrics towards the upper tail of the exposure distribution.…”

“…adults at 217 houses across the contiguous USA, Rankin et al (25) reported that average personal magnetic field exposures and long-term fixed site measurements inside the home were strongly correlated (Pearson's: 0.74, Spearman's: 0.78). Based on these results, one may argue that investigators could rely on an area measurement inside the home instead of personal data if there is interest in average exposures among adult men or women.…”

Residential Magnetic Fields and Measures of Neutral-to-Earth Voltage: Variability Within and Between Residences

“…The temporal cycles observed in the 1,000-Home Study parallel those reported in this paper with respect to magnetic fields attributable to transmission lines, distribution lines (whether one, two or three phases, overhead or underground), and grounding currents (whether from distribution lines or within residences), although the latter appear to have a less discernible pattern (Zaffanella 1993). Also, in a measurement study using a subset of residences from a study in eight regions of the U.S. (Rankin et al 2002), Kaune et al (2000) reported that the occurrence of transients displayed the same daily pattern as those observed here and elsewhere for power frequency magnetic fields.…”