By Brian Carnell

Monday, January 28, 2002

In January reproductive epidemiologist De-Kun Li released a study of 1063 women in San Francisco purporting to show that exposure to high peak levels of electromagnetic fields dramatically increased the risk of miscarriage. But other researchers urge caution noting that previous studies purporting to show a connection between miscarriage and EMF later proved to be unfounded.

Most studies of EMF exposure measure or estimate the average exposure. In Li's study, however, women were asked to wear a meter that measured electromagnetic fields, and Li focused on the peak magnetic field the women were exposed to rather than average exposure over time.

Li's research found that women exposed to high peak fields were three times as likely to have a miscarriage compared to women who were exposed to lower peak fields.

Li believes his study breaks new ground. "People have never looked at peak EMF's before," Li told New Scientist. "My study opens a new chapter for these EMF effects. Not just for miscarriages, but for other health effects."

But does it?

Yale University epidemiologist Michael Bracken told New Scientist that he worries that such studies might scare people before they have been adequately investigated. Bracken said,

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. There's a real risk in these things getting over-interpreted and scaring the dickens out of people.

The obvious concern is whether or not Li has properly controlled for confounding variables. University of North Carolina in Chapel Hill epidemiologist David Savitz noted, for example, that women with health pregnancies tend to have a lot of nausea. But that nausea could make women with healthy pregnancies more likely to stay at home more and be less active, thereby reducing their exposure to EMF.

Michael Clark of Great Britain's National Radiological Protection Board warned that previous studies linking EMF to miscarriages had later been found to be a result of just such issues. Clark said,

A few years ago there were studies which resulted in scare stories about VDUs [computer monitors] and miscarriages which turned out to be mistaken when confounding factors were analyzed independently.

Lets see this study replicated and independently analyzed before running off with a new round of EMF scare stories.

Sources:

Warning over miscarriage research. The BBC, January 9, 2002.

Electrical appliances linked to miscarriages. Anil Ananthaswamy, New Scientist, January 10, 2002.

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