Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!spool.mu.edu!cs.umn.edu!uc!shamash!timbuk!dadams
From: dadams@cherry10.cray.com (David Adams)
Newsgroups: sci.electronics
Subject: Re: Re:High Tension Wire Hazards
Message-ID: <113351.25560@timbuk.cray.com>
Date: 23 Apr 91 17:33:15 GMT
References: <4045@anasaz.UUCP>
Reply-To: dadams@cherry10.cray.com (David Adams)
Organization: Cray Research, Inc.
Lines: 105


In article <4045@anasaz.UUCP>, John Moore writes:
|> In article Message-ID: <112256.27482@timbuk.cray.com> dadams@cherry10.cray.com (David Adams) writes:
|> 
|> >Yesterday I heard a report on the radio about a study on the 
|> >Hazards of living near high tension wires.
|> >
|> >The study involved, the report pointed out, was not scientific!
|> >In order to perform a valid scientific study on the subject
|> >we would have to obtain a random sample of children, randomly
|> >assign half of them to live near high tension wires and the 
|> >other half away from high tension wires.  Then we follow the
|> >progress of these children over the course of many years and
|> >measure the proportions which develope cancer, etc.
|> 
|> This is not true. In order to perform an OPTIMAL experiment on the
|> subject, we might have to do as you say, but valid science is often
|> done with skimpy data.
|> 
|> >
|> >We cannot do this in a democratic society.  So what the researchers
|> >did was to find a group of people who had developed some disease.
|> >(I don't remember what disease was involved.)  Then they tried to
|> 
|> Childhood Leukemia - if you are referring to the Denver study.
|> 
|> >find a *similar* group of people who did not develope the disease.
|> >Then they looked back to the childhood histories of these people
|> >to see how many of each group lived near high tension wires.
|> 
|> Not high tension wires - simple backyard distribution wires - with
|> different levels of ELF magnetic fields.
|> 
|> >This is not a good scientific method.  It was pointed out, for example,
|> >that it may well be that more affluent people were willing to 
|> >volunteer for the study, and that fewer of these were likely to have
|> >lived near high tension wires.  When you set out to find a *similar*
|> >group, it is entirely impossible to consider all of the variables
|> >that might be involved.  This is one of the reasons that randomization
|> >is so critical.
|>  
|> >When I see so many people begin to believe conclusions that come 
|> >from bogus studies, it really makes me stop and think.  We need to 
|> >learn to be critical when we read, or evaluate a study like this one.
|> >This doesn't mean that High Tension Wire Hazards do not exist, but
|> >we cannot use the conclusions of experiments like these as evidence
|> >that they do.  
|> 
|> Self selection is always a risk in epidemiological studies. It does not
|> mean that the study is incorrect - it does mean that the results may
|> not be as conclusive as would be with the sort of experiment that you
|> admit cannot be run. It does not mean we should simply ignore the
|> studies or not try to run them. 
|> 
We can't help but look at the conclusions with a jaundiced eye.

|> Modern medical science would be seriously crippled -where without these 
|> studies. I would point out that your criticism also applies to most 
|> smoking-->cancer/smoking-->heart_disease studies. Try to eliminate self
|> selection from a risk of smoking epidemiological study! Does that mean that 
|> we are foolish to believe them, or that we should not act upon them?
|> 

We are foolish if we act on that study alone, or on a group of similar 
studies, especially when most of these studies are marginally significant.
Many of the studies done on smoking probably are weak.  I am not the first
to level such criticism.  This does not imply that smoking does not cause
cancer/heart_disease etc, and it doesnot mean that we should not act to prevent 
a forseeable danger.  Furthermore, the evidence in the case of smoking, I 
beleive, is much stronger than for magnetic fields.  Has any one preformed 
randomized experiments with magnetic radiation with animal subjects, at doses 
that are comparable to those received by humans?  Again it may be a jump to 
make inferences from rabbits, mice, and mink, to humans, but the significance 
levels can at least be established.  If we could see studies of this nature, 
that corroborate those studies which have been done, we might be on a *little*
firmer ground. 

|> While the best statistical results come from a pre-designed, randomized,
|> multiple-blind study, we are not always in a position to do such a study.
|> Sometimes we have to use what data is available, with recognized corresponding
|> degradation in experimental accuracy. One of the most powerful challenges
|> in science is designing statistically valid experiments under these
|> conditions - and some people are amazingly good at these experimental
|> designs.
|> 

The problem is that people don't recognize the corresponding degradation in
experimental accuracy, in fact mathematicians can't even tell what it is!
(Ie.  If you forget to randomize can you say that you are 80% confident
instead of 95% confident?  No! You can't say anything about confidence 
at all!) Yet people make very serious decisions on the basis of such weak
conclusions, not even knowing the weakness was there.


|> None of what I say above means that I take these studies uncritically. The
|> Denver study in particular was just barely statistically significant (like
|> a lot of cold-"fusion" studies were!). It may be wrong. It may also be
|> right. It is backed up by some other epidemiological studies (also 
|> perhaps flawed) and some experimental lab work (that is a lot more solid).

None of what I say above means that I do not believe that hazards from
electromagnetic radiation exist.  Perhaps some of these other studies
are on firmer ground?  I am not familiar with them.  To date, I do not
believe that any of the studies I have heard of *should* affect property
values.