Rate of occurrence of transient magnetic field events in U.S. residences

Abstract

Recent interest in the transient magnetic field events produced by electrical switching events in residential and occupational environments has been kindled by the possibility that these fields may explain observed associations between childhood cancer and wire codes. This paper reports the results of a study in which the rate of occurrence of magnetic field events with 2–200 kHz frequency content were measured over 24 h or longer periods in 156 U.S. residences. A dual‐channel meter was developed for the study that, during 20 s contiguous intervals of time, counted the number of events with peak 2–200 kHz magnetic fields exceeding thresholds of 3.3 nT and 33 nT. Transient activity exhibited a distinct diurnal rhythm similar to that followed by power frequency magnetic fields in residences. Homes that were electrically grounded to a conductive water system that extended into the street and beyond, had higher levels of 33 nT channel transient activity. Homes located in rural surroundings had less 33 nT transient activity than homes in suburban/urban areas. Finally, while transient activity was perhaps somewhat elevated in homes with OLCC, OHCC, and VHCC wire codes relative to homes with underground (UG) and VLCC codes, the elevation was the smallest in VHCC and the largest in OLCC homes. This result does not provide much support for the hypothesis that transient magnetic fields are the underlying exposure that explains the associations, observed in several epidemiologic studies, between childhood cancer and residence in homes with VHCC, but not OLCC and OHCC, wire codes. Bioelectromagnetics 21:197–213, 2000. © 2000 Wiley‐Liss, Inc.

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.…”

“…Factors that were reported as not associated with the wire code included total harmonic distortion (Rankin et al 2002) and resonant conditions . Kaune et al (2000) reported that transients were positively correlated with the residential magnetic field and tended to occur at a lower rate in the lower wire categories; however, these relationships were attributable to the higher rate of transients in homes with conductive grounds (mentioned above). Using data from an exposure assessment across eight regions of the U.S. in which measurements were taken for a 2-d period in 218 residences visited three or four times over an approximate 18-mo period (Rankin et al 2002), there was no evidence that the first difference was related to personal magnetic field exposure or to Wertheimer-Leeper wire code.…”

“…Though they could not ascribe a specific (or definitive) basis for their observation (contact voltage was not mentioned), this is the only epidemiology study to offer even a hint of a suggestion that an exposure linked to the grounding system may be responsible for the association of magnetic fields with childhood leukemia. Subsequently, Kaune et al (2000) reported that residences with a conductive residential grounding system experienced a significantly greater rate of occurrence of transients compared to homes with a non-conductive water system.…”

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

“…During the latter portion of the LTWC study, a small magnetic -field transient counter was deployed during measurement visits. Results of the transient measurements are reported in Kaune et al ( 2000 ).…”

A richer conceptualization of ?exposure? for epidemiological studies of the ?EMF mixture?

“…In the Bowman et al [1995] and Kaune [1994] studies, resonance also did not explain away the wire code or spot measurement associations and we did not consider it as a prime contender to explain previous epidemiological ®nd-ings. A recent study by Kaune et al [2000] suggests no association between wire code and the occurrence of transients, which makes transients a less likely candidate to explain previous epidemiological associations.…”