From:
http://www.newscientist.com/news/news.jsp?id=ns99991769

Electromagnetic fields from appliances linked to miscarriage

09 January 02
Anil Ananthaswamy, San Francisco

The strong magnetic fields produced by some electric appliances and vehicles
increase the risk of miscarriage, claim researchers in California. Their
findings also suggest that most previous investigations into the health
effects of electromagnetic fields (EMFs) have been measuring the wrong
thing.

"The studies really represent state-of-the-art research into the causes of
pregnancy loss," says epidemiologist David Savitz of the University of North
Carolina in Chapel Hill. Nevertheless, he says the researchers'
interpretation of their findings may be wrong. California is already
initiating public hearings to discuss the findings.

One study was led by De-Kun Li, a reproductive epidemiologist at the Kaiser
Foundation Research Institute in Oakland, California. His team asked 1063
women around San Francisco who were in the first 10 weeks of pregnancy to
spend a day wearing a meter around their waists that measured magnetic field
levels every 10 seconds.

Overall, they found that women exposed to peak levels of 1.6 microteslas or
greater were nearly twice as likely to miscarry as women not exposed to such
strong fields.

More significantly, says Li, among the 622 women who said the measuring
period had been a typical day, those who experienced high peak fields were
three times as likely to have a miscarriage. "That's another confirmation
that the effect is due to EMF," says Li.

Shavers and hairdryers

Other factors can have a more dramatic effect, however. The risk of a
miscarriage increases tenfold as women age, for example, from 5 per cent for
women under 30 years old to 50 per cent for those in their mid-40s.

Li's team didn't look at what was producing the fields, but appliances such
as shavers, hairdryers and vacuum cleaners can produce strong alternating
magnetic fields, as can electric vehicles such as trams and trains. The key
is proximity to the source, as fields drop off rapidly with distance.

Alternating magnetic fields also have associated electric fields. The few
previous studies of the effect of low-frequency EMFs on miscarriages, such
as one involving 727 women done in 1991 by Raymond Neutra's group at the
California Department of Health Services in Oakland, have been inconclusive.

But Li thinks this is because Neutra looked at people's average exposure to
electromagnetic fields over time, not peak values. "People have never looked
at peak EMFs before," Li says. "My study opens a new chapter for these EMF
effects. Not just for miscarriages, but for other health effects."

EMF spikes

When Neutra reanalysed the data from his earlier study, which has only now
been published, he discovered the results were similar to Li's. Women
exposed to peak EMF levels greater than 1.4 microteslas were nearly twice as
likely to miscarry.

But Savitz sees things differently. "Both studies found a reassuring lack of
association for the most well-established measures of magnetic field
exposure, that is average magnetic fields." The correlation between
exposures to EMF spikes and an increased miscarriage rate may be due to
other factors, he says. For instance, women who have a healthy pregnancy are
more likely to suffer from nausea. This may make them more likely to stay at
home and do less, and thus also reduce their exposure to magnetic fields.

After Savitz's comments, Li's team looked at their data again. They also
checked for other possible risk factors such as drug use, carrying heavy
loads and previous induced abortions. "We adjusted for 30 different kinds of
risk factors. Nothing changed," says Li.

Localised heating

But Michael Bracken, an epidemiologist at Yale University, is unconvinced.
"There are numerous ways of measuring these fields, and one worries that if
you do it enough times, then you are going to find positive associations,"
he says. "There's a real risk in these things getting over-interpreted and
scaring the dickens out of people."

In the past, EMFs have been blamed for various other ill effects, especially
leukaemia in children. But no one can explain how relatively weak fields
might cause the DNA mutations that lead to cancer, and most studies have
failed to find evidence of a link.

The peak values measured by Li are way below the recommended exposure limit
of 1600 microteslas. Above this level, EMFs can induce electric currents in
the body, which leads to localised heating. Li speculates that EMF spikes
could cause miscarriages by subtly disrupting cell-to-cell communication.
"But as epidemiologists, we should not feel weaker because we don't
understand the mechanisms."

Journal reference: Epidemiology (vol 13, p 1, 9 and 21)