Re: Power Lines and Magneti

[John Moulder <jmoulder@post.its.mcw.edu>]

> The matter of transients is treated by the report of Ben Armstrong 
> and colleagues in Am. J. Epidemiol. vol 140, pp805-820, 
> November 1, 1994, reporting that utility workers exposed 
> to short-duration pulsed electromagnetic fields (PEMFs) had 
> significant increases in lung cancer.  

Hold the presses on this one.  

The "PEMF" dosimetry for this study is based on readings from "detector three" 
of the Positron dosimeter (detectors one and two report the electric and 
magnetic fields).  This so-called HFT (high frequency transient) channel was 
designed to respond to signals having an E-field component greater than 200 V/
m at 2-20 MHz.

Turns out that the HFT channel doesn't respond at all like its supposed to (3 
reports at the Albuquerque meeting). First of all, in the utility environment 
they respond poorly to switching transients, one of the very things they were 
supposed to measure.  Second, their actual response range goes clear up to 400 
MHz, with peak sensitivities at 14, 145 and 300 MHz.  Third, as the frequency 
increases the detection threshold drops to as low as 5 V/m. 

The result is that "channel 3" is exquisitely sensitive to CW radio 
transmissions in the frequency band near 150 MHz, a band that is heavily used 
for amateur and commercial radios, and is now (but only recently) heavily used 
for portable radio communication in the utility industry.

So the job categories in which the Armstrong et al study is reporting PEMF 
exposure and excess lung cancer, are actually the jobs that involve use of, or 
proximity to use of, portable radios.  But keep in mind that the vast majority 
of the reported excess lung cancer occurred before the use of these radios 
became common in these occupations.

Such are the hazards of doing epidemiology when the underlying biology and 
physics are so poorly understood.

John Moulder (jmoulder@its.mcw.edu)
Maintainer:  Powerlines & Cancer FAQs
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