At 02:37 PM 8/27/2006, Gayle Kaye wrote:
>I found you by doing a search on google . I am just plain ol'John Q.
>Public who's trying not to panic. So try to use some plain talk. It
>would be appreciated. I am good with a dictionary.
>
>I just heard there is going to be a 500kV high tension wire built in
>our valley to help bring more electricity to the "city" 12 miles
>away. Of course I chose to live in a semi isolated area because I
>like it and feel upset by this "major intrusion." My question to you
>is about the safety of this "wire" being put through our valley, and
>how concerned should we be?
The safety of the line is probably related to things like construction
equipment when they build it, more than anything else.
>Not being an expert on electricity and it's effects I am looking for
>some information so I can be informed rather than just plain scared.
>I have two girls 11+14, livestock, and an orchard that helps to
>supplement my lively hood as a teacher. How concerned should I be?
>The wire will be about 5-700 feet from my house. there about 30 homes
>where it will pass and being a small town the is of course some
>hysteria going on. Please let me know your opinion or where i can get
>some information to be able to conclude my own opinion.
There was a widely publicized sensational book more than a decade ago
called "Currents of Death", virtually all the claims of which were either
subsequently refuted or found to be the result of something else. I'll
give some specific examples lower down, but, you should bear in mind that
these kinds of books tend to live on for a long, long time, particularly
since they pop up everytime someone googles it. These sorts of things are
good for news ratings too: "new power line responsible for increased
cancer? Find out at 11!" (never mind that the story at 11 says nope, it's
not..)
>Thanks,
>Trying not to panic,
>Gayle
Don't panic..but be aware...
Here's the overall scoop.
40 odd years ago, someone did a statistical analysis of occupation and
cancer incidence and found that people who worked in electrical switchyards
and similar occupations had a slightly higher incidence of cancer. (along
with lots and lots of other professions..) At that time, they hadn't
controlled the statistics for things like age, smoking, income, etc. all
of which have huge effects on cancer incidence. No big deal in general..
there are analyses like these all the time, insurance and public policy
folks use them to set rates, figure out how much to budget for health care,
predict future population.
About 10-15 years later (now about 20 or more years ago), someone said,
hey, what if the thing for switchyard workers is due to electric
fields? So they figured, if we look at other populations that are exposed
to high fields, we should see an increase in cancer. Then, because at the
time, actually measuring the fields was expensive (we're talking about a
couple grad students and a professor doing the research essentially part
time), they figured, if we get a map of Denver and the surroundings, and
assume that power lines result in fields (not necessarily valid) then we
might see a correlation between how close you live to a power line and
cancer incidence. Remember, this is back in the days when PCs were brand
new, so most of the work was done manually, and there were lots of
approximations. They took regions of the city for which they had cancer
statistics, and measured the distance to power lines with a map. Sure
enough, they found a correlation.. they published a paper, and it got
picked up by the news.
What that study did NOT do (and to give the authors credit, they were very
careful to say so in the paper) was:
1) Figure out if there was some other reason there might be a higher
incidence. Notably, neighborhoods with power lines have lower housing
prices (because the lines are ugly), which means that people with lower
incomes live there. Lower income is definitely correlated with higher
cancer (less access to health care, more carcinogen exposure at work, etc.)
2) Actually measure the fields.
The other very important thing is that nobody was proposing a credible
biological mechanism by which the fields might cause cancer.
This story came out at a time when PCs and video display terminals (VDTs)
were becoming much more common at work, and people were reporting aches and
pains and "weird things" that they attributed to electromagnetic radiation
from the displays. The most famous study there is the Kaiser study that
showed a correlation between VDT usage and miscarriages. If you recall,
there was a bit of a recession around then, so things like this also wound
up be used as a negotiating tool by unions: We deserve a raise because
you're killing us with EMF from terminals. {Turns out in the various VDT
and PC studies they eventually attributed the problems to ergonomics..
people aren't designed to sit in traditional deskchairs staring at a screen
all day...}
So there was a lot of attention to fields and health. And a lot of news
stories. And a lot of people jumping on the bandwagon to survey your house
or business for fields, for a nominal fee, etc.
Subsequent to all this (in the last 10-15 years) there have a been a
variety of very well done studies, where they actually measured the
electric fields, and controlled for previous health history, occupation,
etc. The result of all this is that all the studies have found is that
there is no statistically significant increase in cancer due to living
under a power line, at least from the electric fields. Sure, there are
increases, sometimes (but there are also decreases.. they don't get on the
news), but they can be attributed to things like income, environmental
contaminants, and the like.
This is not to say that a power line is a wonderful thing to live next
to. It IS sort of ugly. It does make noise (crackling and hissing when the
weather conditions are right). It's real, real visible, so it can be used
as an excuse for something else someone doesn't like. The construction
process can be disruptive, noisy, etc., like any construction (although
these days, with helicopters, they can drop in new lines without having to
bulldoze huge swaths of the countryside). And older power lines may be
associated with industrial contamination with things like PCBs (which were
used for insulation in big transformers, and the like), not to mention just
plain old stupid (in retrospect) things like using PCB contaminated oil as
a spray to keep the dust down on the access roads. This sort of thing is
quite unlikely in today's regulatory environment.
There are also legal restrictions on what you can and cannot build directly
under the line. For instance, around here (southern California), you can't
build a permanent structure, so you see lots of wholesale nurseries,
christmas tree farms, and pipe corrals for horses and livestock under the
lines.
There's a very authoritative source of information on the power line/cancer
thing at:
http://www.mcw.edu/gcrc/cop/powerlines-cancer-FAQ/toc.html
As for aesthetic concerns and stuff surrounding construction hassles,
you're sort of on your own. The power company engineers tend to look at HV
transmission lines as things of beauty and good engineering, particularly
if the technology is novel or the route particularly rugged and
challenging. They also tend to be pretty focussed in on the cost/benefit
ratio.. they solve problems with getting power from here to there, and to
most engineers, that's a good thing.
Good luck, and feel free to ask questions..
James Lux, P.E.
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