A Report on Non-Ionizing Radiation

Keep That Laptop Off Your Lap

At least until a new generation of researchers give us some answers

August 13, 2005

The inside back cover of the August issue of Wired has an ad with a picture of a model who has a laptop on her belly. She’s got a big grin on her face —apparently because her computer is protected with Symantec’s anti-spyware and anti-virus software.

Putting a laptop on your body may be okay for a photo shoot, but it’s probably not such a good idea to leave the computer there for a long time. In addition to delivering heat to sensitive organs, there can be significant exposure to EMFs.

In fact, it’s probably not a good idea to keep any electronic or electric appliance flush to your body on a regular basis.

Let me be clear: We don’t know whether EMFs from appliances are a health hazard. What we do know is that some appliances give off strong localized fields with complex waveforms. While they diminish very quickly with distance, up close they can pack a wallop.

We also know that a discomfortingly large number of epidemiological studies show that long-term exposure to low-level EMFs is linked to childhood leukemia —the implicated levels are 250 times lower than the current limit for exposing children 24/7 and more than a 1,000 times lower than the occupational guidelines. (The U.S. has never adopted an EMF exposure standard.)

In addition, we know that the use of certain appliances has been associated with cancer. For instance, a 1998 National Cancer Institute (NCI) study showed that children exposed to electric blankets, hair dryers or video games had significant higher rates of acute lymphoblastic leukemia. A number of other appliances, including curling irons, were also linked to cancer.

But there were inconsistencies. The risk associated with years of use was often similar to that from short-term use —that is, there was no dose-response relationship. But that said, looking at all the NCI appliance data, you will see a large number of statistically significant elevated risks of childhood leukemia and it’s hard to escape the conclusion that something is going on.

The NCI team, however, focused on the inconsistencies, threw up their hands and concluded there was nothing to worry about.

Earlier this year, the NCI published another study which linked the use of electric hair dryers and shavers with brain tumors. (Men who used electric shavers had ten times more meningiomas!) Once again, the NCI decided that it was “unlikely” that there was a true association.

One major problem with both NCI studies is that the EMFs from the appliances were not measured. The NCI team assumed that the magnetic fields from a hair dryer are identical to those from a fan or a microwave oven, except in terms of the intensity of the field. This is a primitive, though not uncommon, approach among EMF researchers. But it’s like studying particulate air pollutants without specifying the size or the chemical composition of the particles. You might get an idea about effects, but it would be a very rough estimate.

By neglecting the differences among the different types of EMFs, the NCI team assumes that all appliances are sources of simple sinusoidal 60 Hz magnetic fields. No allowance is made for fields whose frequency and intensity fluctuate over time, whether other frequency components and transient are present, or whether the resulting exposures are intermittent. (In the more recent paper, the NCI team does acknowledge that hair dryers and shavers give off high-frequency transients). Another ignored variable is the polarization of the field.

Elizabeth Ainsbury, an English doctoral student of Denis Henshaw’s at Bristol University, illustrates the variation in polarization of the magnetic fields associated with appliances in a paper published recently in Physics in Medicine and Biology. She reports, for example, that microwave and electric ovens have the most elliptically polarized fields, while alarm clocks have the least ellipticity.

(As the field becomes more circularly polarized —that is, as it become more elliptical— the greater the potential for depositing its energy into those exposed, see MWN, M/A00, p.1.)

Ainsbury concludes that her measurements

“demonstrate that domestic magnetic fields are extremely complex and cannot simply be characterized by traditional measurements such as time-weighted average or peak exposure levels.”

Could polarization be the missing variable that, if taken into account, would clarify the existing epidemiological and experimental data? It’s far too soon to tell, but it is a tantalizing possibility.

For a long time, many have speculated that EMF epidemiological studies are cloudy because some characteristic of the field has been left out. It is as if we are looking through a distorted prism. But with the right set of filters, we could see the EMF risk more clearly.

Five years ago, Jim Burch showed that workers exposed to circularly or elliptically polarized fields were more likely to have lower melatonin levels. And years before that Masamichi Kato in Japan reported a similar finding in animals (see MWN, M/A00, p.4).

Back in 2000, Burch told us his results “definitely need to be followed up.” They weren’t. (Burch has recently moved to the University of South Carolina.)

With progress coming in five-year intervals it is going to take a long time to sort all this out.

Joe Bowman at NIOSH in Cincinnati is hopeful however. “I’m encouraged to see an EMF health study measuring more than just the time-averaged magnetic field,” he told Microwave News in a recent interview. “Studies like Ainsbury’s will hopefully lead to a new generation of more informative epidemiologic studies.” Bowman is himself designing an epi study using the Multiwave meter developed by Electric Research, which can measure a number of field parameters including polarization. Ainsbury also used the Multiwave.

Clearly, there is much more work to be done. And until we learn more and can see the EMF problem more clearly, it’s probably a good idea to keep your laptop off your lap —especially if that computer is broadcasting RF radiation through its wireless connection to the Internet.