Possible effects of ELF (was Re: Effects of RF energy) 
Author Message
 Possible effects of ELF (was Re: Effects of RF energy)



part:

Quote:

>> The correlation I referred to was originally published by Wertheimer
>> in the 1970s, I think it was, and was replicated by the Electric Power
>> Research Institute (in the last few months of 1990).

        Wetheimer, et al studied 60Hz effects.  Not RF.

Quote:
>I hope that you mean that the study was replicated.  Wertheimer's  claims were
>that the electric fields inside the house from the wiring layout and such
>things as electric blankets was causing cancer.  When I saw her paper, the data
>sets that she had I believe only contained 8 children each, and I believe that
>the statistical correlation depended on 1 extra cancer case in the study group
>ove the control group.  

        My recollection was the "high field" cases were twice the "low field"
        cases, BUT that the number of cases of cancer in BOTH was so low, that
        the standard test for statistical significance was only met by _one_
        case.  That is, if there had been one less cancer case, the results
        could have happened by chance.  In any case, Wertheimer, et al, made
        no effort to screen for other causes (confounders.)

Quote:
>> The correlation Wertheimer reported was between field strength and indicence
>> of leukemia;

        Not exactly.  The study was done on a shoestring.  NO FIELD MEASURING
        EQUIPMENT WAS USED.  They estimated what they thought the fields would
        be, based on assumptions about the current levels and observations about
        the physical arrangements of the wires.

Quote:
>> the EPRI study found a weak correlation between field strength
>> and a higher correlation between physical setup of the electrical
>> supply to the homes. It's not high voltage at a distance being referred
>> to in either case.

        I _think_ Wertheimer, et al, did have "categories" for higher voltage
        lines, if present.  In general, most of their data were from low voltage
        (110/240VAC) lines.  Most of the "lab data" (tissue cultures, etc) that
        show any positive correlation do so for magnetic, not voltage, fields.

Quote:
>I remember the supply correlation, but I thought that there was no correlation
>with internal wiring.  I thought I remember that disappearing in the followup
>studies.

        Everything i have seen, shows that the correlation is very weak, if
        present at all.

        Another "study of studies" showed that as more studies were done, each
        later study showed a _smaller_ correlation.  There is much work to be
        done.

thanks
dave pierson                    |the facts, as accurately as i can manage,
Digital Equipment Corporation   |the opinions, my own.
600 Nickerson Rd
Marlboro, Mass

"He has read everything, and, to his credit, written nothing."  A J Raffles



Wed, 13 Jul 1994 02:16:08 GMT
 Possible effects of ELF (was Re: Effects of RF energy)

Quote:

>    My recollection was the "high field" cases were twice the "low field"
>    cases, BUT that the number of cases of cancer in BOTH was so low, that
>    the standard test for statistical significance was only met by _one_
>    case.  That is, if there had been one less cancer case, the results
>    could have happened by chance.  In any case, Wertheimer, et al, made

        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Quote:
>    no effort to screen for other causes (confounders.)

Wrong.  I know what you mean, though.  The one cancer case reduced the
probability of a similar or more extreme event happening *in the chance
model adopted* from just over 0.05 to just under 0.05.  The standard
procedure then seems to be that one assumes in such cases:
  (1) The probability model for all events (including the experimental
      setup) leading to the observed events is entirely correct, or at
      least has a negligable chance of being wrong;
  (2) Anything with a modeled probability of under 0.05 can't happen at
      all.

Something I'd like to know (I haven't seen the Wertheimer en Leeper
paper and where I can find the follow-ups I'd love to know) is: was
the research by W&L maybe undertaken in a neighborhood where the
researchers accidentally had noticed a few cancer cases close to
power lines?  I seem to remember such a thing.
In that case any significance testing is rubbish; the theory applies
to the situation that you have a hypothesis first, and devise and apply
a test afterwards *with entirely fresh data*, and not using any of the
data that gave you the idea of formulating the hypothesis.

JWN



Wed, 13 Jul 1994 22:44:31 GMT
 
 [ 2 post ] 

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