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From: pierson@cimcad.enet.dec.com (Dave Pierson)
Newsgroups: sci.electronics
Subject: Re: Re:High Tension Wire Hazards
Keywords: stray fields
Message-ID: <22148@shlump.nac.dec.com>
Date: 17 Apr 91 23:17:14 GMT
Sender: newsdaemon@shlump.nac.dec.com
Organization: Digital Equipment Corporation
Lines: 69

In article <4023@anasaz.UUCP>, John Moore writes an, in my opinion, EXCELLENT,
summary of the situation, from which i quote, in part:

>  (2) All of the evidence that I am familiar with deals with the biological 
>      effects of ELF MAGNETIC fields, not electric fields. 
	Second this.  And the studies showing effects, in lab settings, are much
	stronger than the links to electric fields.

>  (4) Evidence includes:
>      -Epidemiological studies showing correlations between ambient magnetic
>       field strengths (at 60Hz) and childhood leukemia. The herbicide
>       explanation fails to explain this - there is no reason to expect,
>       in the study that was done in Denver, that herbicide application
>       would correlate with residential neighborhood field strengths. However,
>       it may be that PCB exposure would - the highest fields were nearest the
>       transformers, which may have contained PCB's. I would be interested if
>       some knowledgeable person on the net could respond to the PCB
>       conjecture.
	There are a couple of interesting things i have heard from professional
	studies of the Denver (and similar Southern California studies).  I do
	not have sources, but the speakers were professionals:
		1) As John points out, the Denver correlation was weak.  I
		believe it was one case away from being statistically
		insignificant.

		2) In the case of the Denver studies (Wertheimer(?) et al) no
		field strength measurements (electric or magnetic) were done.
		When, after the fact, (some years after the fact) a seperate
		study revisited the same locations to measure the fields
		(magnetic only) they found no correlation between the (later)
		field strengths and the earlier leukemia rates.  This is not,
		obviously, "cast iron", it is intriguing.  What is curious is
		that the "California" study found the same effect, with much
		less time lag between measurement of field and diagnosis of
		leukemia:  A weak correlation between postion of wiring and
		leukemia.  NO correlation between measured field strength and
		leukemia.
>  (5) We are talking about a very WEAK effect here. By that I mean that the
>       risk is very small. I realize that to someone whose child develops
>       leukemia, this is small comfort.
		From memory, the strongest correlation found was a doubling
		of the risk.  By comparison, the first study of smoking and
		cancer showed a ten times increase.

>  (6) There is a popular book out that covers this controversy. It is by
>       Paul Brodeur, and the name escapes me right now. It has interesting
>       data in it, although I should caution that it is, too me, irresponsibly
>       sensationalist and alarmist - and FAR from scientific. It does, however,
>       give pointers to where to find the real scientific literature.
		Currents of Death.  I have not read it, but assume it covers the
		same ground as Brodeur's extended three-parter in June, 1990
		issues of New Yorker.  I was less than overwhelmed by the New
		Yorker article.  As to pointers, Brodeur, interestingly, fails,
		I understand, to mention the existence of a professional journal
		(name escapes me...) dedicated to the field.  Curious omission.

If it hasn't been mentioned, the Office of Technolgy Assessment, an arm of the
US Congress, prepared a survey, ca 100 pages, ca 1989.  The exact title escapes
me (Biological effects of ELF Fields, perhaps?), about $8 from the US Government
Printing office (if its in print, it was last summer).  Value for money, with
extended footnotes and bibliography.  This is not the "delayed" report.

thanks
dave pierson			|the facts, as accurately as i can manage,
Digital Equipment Corporation	|the opinions, my own.
600 Nickerson Rd
Marlboro, Mass
01752				pierson@cimnet.enet.dec.com
"He has read everything, and, to his credit, written nothing."  A J Raffles