Linked to Miscarriage Risk
NEW YORK (Reuters Health) - In findings certain to add to the
controversy over the health risks of electromagnetic fields (EMFs)
emitted by power lines and electrical appliances, two new studies
suggest that women briefly exposed to very high-intensity EMFs
have an increased risk of miscarriage.
The findings are preliminary, but one of the investigators told
Reuters Health that women concerned about the risk may want to
stand at arm's length from electrical appliances at home and work
to minimize the potentially harmful effects of EMFs.
Despite the new research, however, the evidence that EMFs increase
the risk of miscarriage is far from conclusive, according to a
North Carolina researcher.
A variety of sources can produce EMFs, including power lines,
computer monitors, microwave ovens and photocopying machines.
Their relationship to health problems has been uncertain and controversial.
For example, some research has linked EMFs from power lines to
a slightly increased risk of childhood leukemia, but other studies
have failed to show this connection.
Only a handful of studies have examined the possible link between
EMF exposure and miscarriage risk. Two reports in the 1980s found
that using an electric blanket could increase the risk of miscarriage,
but the results of more recent studies have been mixed.
Problems with the way previous studies have been conducted may
help explain the conflicting results, Dr. De-Kun Li of the Kaiser
Foundation Research Institute in Oakland, California, told Reuters
Health in an interview. Li is the author of one of two studies
on the association between EMFs and miscarriage that are published
in the January issue of the journal Epidemiology.
In that study, Li and his colleagues tried to address some of
the flaws of previous research. Instead of looking back at a woman's
exposure to EMFs after she had had a miscarriage, the researchers
followed nearly 1,000 women beginning in early pregnancy.
Li said he and his colleagues used a better method of measuring
EMFs--a tracking device worn on the body for 24 hours--than previous
``Our measurement more accurately reflected the true exposure
women get in real life,'' he said.
In Li's study, a woman's average level of EMF exposure did not
seem to have an effect on her risk of miscarriage.
But the researchers did detect a connection when they looked
at the highest level of EMFs that women were exposed to during
the day. Women with a peak EMF exposure of 16 milligauss--much
more intense than what most electrical appliances emit--were 80%
more likely to have a miscarriage than women with lower peak exposures.
This risk ``barely changed'' after the researchers accounted for
about 30 known miscarriage risk factors.
This risk was highest during the first 10 weeks of pregnancy
and it was more pronounced in women with a history of miscarriage
or problems becoming pregnant.
The investigators also found that the link between peak EMF exposure
and the risk of miscarriage was stronger in women who engaged
in their typical daily activities on the day they wore the EMF
monitor, meaning the measurements were more likely to reflect
their actual exposure.
Once Li and his colleagues arrived at their findings, another
set of researchers led by Dr. Raymond R. Neutra of the California
Department of Health Services in Oakland re-analyzed data they
had collected previously. Their analysis also determined that
women with high peak EMF exposures had an increased risk of miscarriage.
Li cautioned that the results of the studies are preliminary,
and need to be confirmed. In the meantime, he said, ``It would
be prudent for pregnant women or women who are planning to get
pregnant to take some simple steps to avoid unnecessary exposure
to magnetic fields.''
Common household sources of EMFs include microwave ovens, electric
can openers, vacuum cleaners, hair dryers, electric fans, washing
machines and dishwashers. Fluorescent desk lamps, electric office
equipment and electrically powered public transit systems also
may emit EMFs.
Completely avoiding all EMF sources is impossible, but Li said,
``The intensity of magnetic fields drops dramatically with increasing
distance from the source.'' For instance, people can drastically
reduce EMF exposure by standing 4 or 5 feet away from a microwave
while it is on, Li said.
But in an editorial that accompanies the studies, Dr. David A.
Savitz of the University of North Carolina School of Public Health
in Chapel Hill writes that the studies add ``only slightly'' to
the evidence supporting a link between EMF exposure and an increased
risk of miscarriage.
The findings may stem in part from ``behavioral differences between
women with healthy pregnancies and women who either experienced
a miscarriage or were destined to have one,'' according to Savitz.
He notes that in Neutra's study, women's exposure was measured
at 30 weeks' gestation--or several months after miscarriage for
the women who had lost their pregnancies. Women this far along
in pregnancy tend to be less mobile than non-pregnant women. So
the women who had already miscarried would probably be more mobile,
and thus more likely to be exposed to EMFs at home, work and other
places, Savitz suggests.
In Li's study, the North Carolina researcher points out that
women's mobility may also play a role. He notes that women who
miscarry are less likely to experience frequent nausea during
``All other things being equal, a woman experiencing nausea will
be less likely to move around her home or workplace or community,
and therefore less likely to experience the diverse magnetic field
sources in those places,'' Savitz writes.
So women who have less nausea, who are predisposed to have a
miscarriage, might be exposed to higher peaks in EMFs in their
daily life, he suggests.
But according to Li, his colleagues accounted for nausea, and
it did not have an effect on the relationship between EMF exposure
and the risk of miscarriage.
And Neutra told Reuters Health that women in his study were just
as likely to experience bursts of high magnetic fields at 12 weeks
of pregnancy as at 30 weeks.
However, Savitz believes the evidence is too slim to warrant
any change in women's behavior or public policy. ``In my view,
the evidence linking magnetic fields to miscarriage is very weak,
below the level at which any sort of policy or behavior change
would be well justified,'' he told Reuters Health.
``Given the unusual measures of magnetic fields of concern here,
brief exposure to high fields or variability in fields over time,
it's very unclear what someone could do to reduce exposure even
if they were motivated,'' Savitz added.
SOURCE: Epidemiology 2002;13:1-3, 9-20, 21-31.
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