Provides a modeling-study abstract proposing contact current as a possible explanation for associations b…

See attached file(s)

The Possible Role of Contact Current

in Cancer Risk Associated With

Residential Magnetic Fields

2000

Residential electrical wiring safety practices in the US result in the possibility of a small voltage (up

to a few tenths of a volt) on appliance surfaces with respect to water pipes or other grounded

surfaces. This ``open circuit voltage'' (VOC) will cause ``contact current'' to flow in a person who

touches the appliance and completes an electrical circuit to ground. This paper presents data

suggesting that contact current due to VOC is an exposure that may explain the reported associations

of residential magnetic fields with childhood leukemia. Our analysis is based on a computer model

of a 40 house (single-unit, detached dwelling) neighborhood with electrical service that is

representative of US grounding practices. The analysis was motivated by recent research suggesting

that the physical location of power lines in the backyard, in contrast to the street, may be relevant to

a relationship of power lines with childhood leukemia. In the model, the highest magnetic field

levels and VOCs were both associated with backyard lines, and the highest VOCs were also

associated with long ground paths in the residence. Across the entire neighborhood, magnetic field

exposure was highly correlated with VOC (r 0.93). Dosimetric modeling indicates that, compared

to a very high residential level of a uniform horizontal magnetic field (10 mT) or a vertical electric

field (100 V/m), a modest level of contact current ( 18 mA) leads to considerably greater induced

electric fields (> 1 mV/m) averaged across tissue, such as bone marrow and heart. The correlation of

VOC with magnetic fields in the model, combined with the dose estimates, lead us to conclude that

VOC is a potentially important exposure with respect to childhood leukemia risks associated with

residential magnetic fields. These findings, nonetheless, may not apply to residential service used in

several European countries or to the Scandinavian studies concerned with populations exposed to

magnetic fields from overhead transmission lines. Bioelectromagnetics 21:538±553, 2000.

ß 2000 Wiley-Liss, Inc.

Key words: magnetic fields; childhood leukemia; power lines; open circuit voltage