We live close to power lines.   The closest point of our home (in the
Master Bedroom)  to the lines read "4" miligauss.  How harmful is
this?

jeannette...

I did some further research on this interesting topic,
and found some startling news from a reputable source,
the California EMF Study, conducted by the California
Health department, as reported on the website of the
Power Line Task Force, Inc:

"The California Health Department final report on power
 frequency EMF was published in October 13, 2002. This
 7-year, $9 million study concludes EMFs can cause some
 degree of increased risk of childhood leukemia, adult
 brain cancer, Lou Gehrig?s Disease, and miscarriage.
 The Evaluation further concludes that magnetic fields
 may cause suicide and adult leukemia."
http://powerlinefacts.com/index.htm

Additionally, the introduction for the EMF page on the
Powerline Facts website notes:

"When properly analyzed, scientific data convincingly
 and consistently show a link between magnetic fields
 greater than 2-4 mG and cancer. New analyses of older
 data have induced a  wholesale revision in the views
 of high-level authorities, including the utilities
 themselves, who have dramatically revised their own
 statements on EMF."
http://powerlinefacts.com/EMF.htm



The full text of the California Study is made available
on the California Department of Health Services EMF
Program website, in PDF format:
http://www.dhs.ca.gov/ehib/emf/RiskEvaluation/riskeval.html



I was drawn to this study by citations made on numerous
concerned environmental sites:

From a post by Joanne C. Mueller, of Guinea Pigs R Us,
in the EMF-Omega-News archives on the Buergerwelle
incorporated society website:

"Gentlemen: I am extremely concerned that the issue of
 children and exposure to electromagnetic fields up to
 4.0 miligauss is not featured on your site. As you are
 most likely aware, the 2002 California EMF Study has
 found that leukemia, brain cancer, Lou Gehrig's Disease
 and miscarriage are more likely than not related to
 chronic, prolonged exposure to EMF;s in the 4.0 miligauss
 range."
More on the page:
http://www.buergerwelle.de/body_news.html


From a post on a Yahoo Health group, citing Microwave News:

"A report of a large epidemiological study reoprted [sic] 
 by Microwave News, the most authoritative publication,
 respected by citizen activists and industry reported
 that at a level of 4 Milligauss there is twice the risk
 of getting Leukemia.
See the report on the page:
http://health.groups.yahoo.com/group/cancercure/message/10905


From a review of epidemiologic studies by Ed Leeper,
author of a how-to guide for reducing EMF, called
Silencing the Fields:

"Both analyses found, among the various studies, a fairly
 consistent indication of tendency toward an elevated
 childhood cancer risk at residential field levels above
 about 3 or 4 milligauss."
http://www.silencingthefields.com/emf-studies.html

It may prove beneficial to look into his book:

"Even the fields that emanate directly from the power
 company lines near a house may be remediable. Although
 often the homeowner's cost for obtaining such changes
 may range from quite high to prohibitive, some changes
 may be as simple as persuading the power company to
 rectify a neutral wire defect or do a better balancing
 of phases on their line.

 In 340 densely informative but highly readable pages,
 the book Silencing the Fields examines all the
 possibilities. Ed Leeper is the physicist co-author
 of several influential early scientific studies
 examining the link of cancer with magnetic fields,
 studies done more than 20 years ago, and he has
 worked actively with the measurement and mitigation
 of AC magnetic fields since then."
http://www.silencingthefields.com/index.html


Other such references can be found in the searches I cite
below.

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Searches done, via Google:

"4 milligauss"
://www.google.com/search?q=%224+milligauss%22

EMF "4.0 milligauss"
://www.google.com/search?q=EMF+%224.0+milligauss%22

"Power Line Task Force, Inc"
://www.google.com/search?q=%22Power+Line+Task+Force%2C+Inc%22

"California Health Department" "final report" EMF "October 13, 2002"
://www.google.com/search?q=%22California+Health+Department%22+%22final+report%22+EMF+%22October+13%2C+2002%22

This might interest you:
http://www.emfacts.com/weblog/index.php?p=110

A couple of years ago a scientist at Lawrence Livermore Labs pleaded
no contest to defrauding the government out of about $5 million in
research money. He falsified the data on his leukemia cluster studies
to continue to receive the funding. Many of the papers and articles
related to leukemia and living near power lines cite his research,
which has since been totally debunked.

Many of the websites quoted here are starting from the assumption that
electromagnetic fields are harmful.  I would be very careful in
reading or interpreting them.  In just 5 minutes, I found many
exaggerations and discrepencies in them, specifically in their
intrepretation of the study done by the California Health Department.

Which study, by the way, is an interesting read: essentially, three
scientists have reviewed the available data and come to the conclusion
that there is reason to believe that EMF can cause an increased
likelihood of certain diseases.  This meta-analysis is NOT
peer-reviewed (meaning that other scientists have not evaluated it for
scientific validity).  Also, the absolute risks of these phenomena are
(according to the study itself), very small, perhaps vanishingly
small.  I include the following quote from the executive summary of
the study:

"With the exception of miscarriage, which is common, the other
diseases for which EMFs may be a contributing cause (childhood
leukemia, adult brain cancer, Lou
Gehrig?s Disease) have low incidence, with rates between 1/100,000 and
1/10,000 a year. Even doubling such rates and accumulating them over a
childhood or a
lifetime leaves accumulated lifetime risks between 1/1,000 and 1%.
Thus the vast majority (99%?99.9%) of highly exposed people would
still not contract these
diseases. Furthermore, calculations suggest that the fraction of all
cases of the above-mentioned conditions that one could attribute to
EMFs would be no more than a
few percent of the total cases (if any). However, if EMFs do
contribute to the cause of these conditions, even the low fractions of
attributable cases and the size of
accumulated lifetime risk of highly-exposed individuals could be of
concern to regulators. Indeed, when deemed a real cause, estimated
lifetime risks smaller than these
(1/100,000) have triggered regulatory evaluation and, sometimes,
actual regulation of chemical agents such as airborne benzene. The
uncommon, accumulated high
EMF exposures implicated by the evidence about these conditions come
from unusual configurations of wiring in walls, grounded plumbing,
nearby power lines, and
exposure from some jobs in electrical occupations. There are ways to
avoid these uncommon accumulated exposures by maintaining a distance
from some appliances,
changes in home wiring and plumbing, and power lines. However, to put
things in perspective, individual decisions about things like buying a
house or choosing a
jogging route should involve the consideration of certain risks, such
as those from traffic, fire, flood, and crime, as well as the
uncertain comparable risks from EMFs."