Monday, August 8, 2011

Talking about wireless: Elizabeth May's advice

Green Party leader and Member of Parliament Elizabeth May recently caused a stir by expressing concern over the safety of electromagnetic radiation. And here she is again this past weekend, taking an interview with her BlackBerry set to speakerphone, to avoid radiation exposure.

I'm not going to go into her concerns about safety (with which I largely disagree; if you're interested in the debate, an excellent summary is here). At the very least, May makes the valid point that there is no scientific consensus on wireless safety.  Fair enough!

But in her longer critique of wireless safety (found here on her blog), and by way of her subsequent actions, May gave some advice to those who are concerned about their exposure to EM radiation. Paraphrasing, she said this:
  1. When using your phone, use speakerphone or text rather than holding it up to your ear.
  2. You can use a smartphone, but don't keep it in your pocket.
  3. At home, use a wireline network, not WiFi.
  4. Don't get a Smart Meter.
What I will talk about is this: for people who are concerned about radio exposure (which doesn't include me), did Elizabeth May give good advice? It seems to me that #1 is good advice, #2 and #3 are questionable, and #4 is wrong to the point of embarrassing.

Let's get this out of the way first: since nobody knows how wireless signals might cause cancer (even assuming they do at all), it's impossible to say for sure.  Even figuring out average exposure is not easy without something like a portable spectrum analyzer, which I don't have.

But in true engineering tradition, I'm going to pick some numbers and try to come up with a back-of-the-envelope answer. I'll make the following assumptions:
  1. Wireless signals obey the inverse square law: for distance d, power is proportional to 1/d^2. This assumption is not always accurate, but it's pretty good under most circumstances. Indoors, it is usually a worst-case assumption -- it will often overestimate your exposure.
  2. All wireless devices transmit with the same power: This assumption is totally inaccurate -- power varies not only by device, but also by type of use (phone, text, browsing, etc.) -- but it's easy to work with. And it's again a worst-case assumption if you're comparing other devices to cell phones, since cell phones generate more radio power than almost any other consumer device. (I'll also make some comments about relaxing this assumption.)
May's first suggestion -- text or use speakerphone rather than hold the phone up to your ear -- is a good one, if you're worried about exposure to radiation. And she seems to be comfortable doing this herself (e.g., in the interview with the Globe), so let's use this as a baseline: on speaker or text, I'll usually hold the phone about 50 cm away from my head, so that gives us a starting point for power comparisons.

How about keeping the phone in a pocket? For one thing, there's nothing but fat, muscle, and skin tissue in your hip, but the links to cancer all focus on the brain -- no worries about cancer anywhere else from any literature I'm aware of. At about 1 m away from the head, a phone in a pant pocket is sending even less "harmful" radiation to the head than on speakerphone: about a quarter the power, since 1 m is 2 times 50 cm, and 2^2 = 4.  And if May doesn't keep it in her pocket, where does she keep it? A briefcase would be better, but if she keeps it in a shoulder bag, it might be even closer to her head than if it was in her pocket. So this is kind of questionable.

What about WiFi? I sit about 1 m away from my computer, and as I type this I'm about 5 m away from my WiFi router. Compared to texting, my computer is about twice the distance away (2^2 = 4, so a factor of 4 weaker); and the router is about 10 times the distance (10^2 = 100, so a factor of 100 weaker). On top of that, WiFi signals are normally much weaker than cell phone signals -- because WiFi is supposed to cover just your house, while cell phones are supposed to cover your whole neighborhood. But even using our worst-case assumptions, and even assuming you stay 5 m away from it all day and don't go outside or anywhere else in your house, your WiFi router is giving you a daily exposure less than that of a 15 minute cell phone call on speakerphone. So if May is okay with using speakerphone, it's odd to me that she would not want WiFi installed in her house.

Finally, let's talk about Smart Meters. These devices use the same family of frequencies as your WiFi router (called the ISM band), and by law their wireless power emissions are constrained: again, worst case, they use about the same power as a cell phone. What's more, the are normally installed outside your house, on the other side of a wall (which itself absorbs 1/2 to 3/4 of the power). And what's more than that, the amount of information they have to send is tiny -- your electricity use doesn't change that fast! -- so they are only active, on average, about 0.1% of the time. So let's consider the worst possible case: the meter is located on the wall directly opposite where you sleep, and your head is more or less right against the wall, about 50 cm away from the meter. Then over your 8-hour sleep, counting the meter's transmitted power, the absorption of the wall, and the meter's low transmission rate, you are absorbing at most the equivalent of a fifteen second cell phone call on speakerphone.

Considering the kind of RF exposure Ms. May finds acceptable, and the kinds of energy conservation benefits that smart meters make possible, this stand against smart meters lacks perspective and is just plain embarrassing. It's the radio frequency equivalent of eating a giant ice cream sundae, then ordering a diet soda because you're trying to cut down on sugar.

1 comment:

ck872 said...

Mr Eckford,

It was good for Eliz. May to broach the topic, to stick her neck out as it were. Too bad she did not deepen her grasp of the issues before doing so. But not only following her intuition, she has justified her own speaking out, if somewhat incoherently as you point out, by pointing to premier recent publications, esp. the Bioinitiative Report (which she had already endorsed as GPC leader a few years ago) and, for political purposes, the Council of Europe May Enviro etc committee doc adopted soon thereafter by their Parl. Assembly, as august a political advisory body as there is. (That in sharp contrast to our own HESA in Ottawa, which I can get more into if you like, which fell flat after hearing much the same expert testimony.) Greens also lead on the issue on Europe.

For all the incoherence, it is rather on the other foot, if you will -- it is all dangerous, all latter-day wireless mania, has been known to be so for decades as well. So good for the publicity she generated, and we hope she goes further, with more understanding, in the fall.

And it is NOT all about power densities, linear dose-response relationships are not the whole of the matter. So much more to say, but let that be a provocative start. You can be referred to a mountain of info.