Tallgirl,
You have raised several good points. You have also (I presume unintentionally) implied that a respected poster a liar, and made your points in ways that imply that the rest of us are kind of dumb and not thinking about things properly. This will have the effect of making us ignore your points, even when they are _very_ good. I don't believe that you've made any _explicit_ claims that anyone here is a liar, but given the imprecision of the English language, it is very easy for people to read offence even when none is intended. Given your background in IT, I am sure you've seen USNET flame wars erupt over misunderstandings of language.
Based upon the studies of EMF, even the worst possible residential exposure (homes under high tension lines and the risk of childhood leukemia) carry much less risk of harm from EMF than driving up to these homes. (Okay, I've not done the math and perhaps this is in fact not correct, but your point that we worry about EMF and not about driving is a _very_ important point.) The fact of the matter is that people get scared of low order unknown risks, and all but ignore real known risks.
This is why my response to the original poster included something along the lines of 'I'd be much more concerned about the PCBs in these transformers than with any EMF from these transformers.'
One of the other points that you have been making is similarly important, though I disagree with you on it.
tallgirl said:
In the case of EMF causing "problems", many of the "problems" are caused by things which are also caused by faulty or improper wiring -- flickering computer monitors, lights,and other such things. [...] So, what's the better explanation -- EMF interacting with some as yet unidentified mechanism in the body resulting in a small fraction of the population being affected by 5 milligauss fields, or the flickering itself, which causes a much larger portion of the population to have an adverse reaction? [...]
I believe that the point that you are making here is that a well identified mechanism is much more believable than a physically unidentified mechanism, this is an important point and I agree with it. However, if a poorly implemented electrical systems generates an EMF field which causes the computer monitor to flicker, which causes the headache, which makes people complain, and correcting the _wiring_ makes the flicker go away, then I would call the flickering monitor the mechanism by which EMF causes problems in this case. Correctly identifying the mechanism makes the issue much less spooky, and identifies multiple approaches that could be used to fix the problem (eg. an EMF resistance monitor rather than reducing the EMF), but in these cases, fixing the poor wiring layout was clearly the best approach.
In the example of the 'woman sensitive to EMF', we don't know if she was somehow _feeling_ the EMF, or if some metal object in the room was resonating at some harmonic of 60Hz, and the tone was particularly annoying to her. A 60Hz magnetic field was measured, and she was able to notice it. When other lights were turned on to reduce the field, she noticed that. There was clear cause and effect. This _was_ an experiment. It was not a properly blinded and controlled experiment, and the placebo effect was certainly in play, and the evidence would not stand up in peer review. But it was an experiment, one that would stand up to the 'make the customer happy' metric.
As a cautionary tail, I suggest looking at the history of 'clock jitter' in digital to analog converters. Back in the mid-80's to mid-90's, there was a considerable amount of snake oil being sold to the audiophile crowd for compact disk systems. Things such as sticky rings to place on the CDs, or 'green pens' to draw on the edges of the CD. These items were being sold with considerable BS. Some people were doing things such as copying CDs to CD-R media, because they found that the CD-Rs sounded better, again with lots of BS. Meanwhile, those 'in the know' were loudly proclaiming that all of this stuff was bunk, that 'bits is bits', and that none of these items could have one bit of effect on the sound coming out of the D to A converter. Finally some competent sound engineers started to do good _blinded_ ABX studies, and found that some people _could_ hear differences between two compact disks which were measurably bit for bit identical.
Once they had this evidence, then they started looking for a physically reasonable mechanism that would explain this reality: that the sound is different despite the fact that the _data_ is correct. The mechanism was in fact astoundingly simple. Proper reconstruction of the analog signal from the digital data requires several things including that the data be correct, which everyone knew wasn't the problem. But too many people made the mistake of thinking that having the data correct was _sufficient_. Additionally the _timing_ of the D/A conversion must be correct, to surprisingly high levels. What was happening was that clock jitter caused by different physical layout of different CDs was putting different jitter on the data clock. The data was exactly the same, but it was coming off the CD with different timing. The net result was that the analog output was _different_.
I strongly suspect that as we more deeply understand the issues of EMF, we will discover unexpected mechanisms which will provide the simplest explanation of what people are seeing, and once we discover these mechanisms we will discover real dangers and real ways to protect ourselves. For now, the danger is slight, the benefits of electricity great, and I for one would be happy to simply remain aware of EMF and eliminate it wherever the cost of doing so is simply having a bit of knowledge.
-Jon
