The answer is education and research. Unfortunately, such things are very hard to do.
Additionally, it is not clear just what the risks are, although it is _very_ clear that the magnitude of these risks is very small. There are no proven mechanisms by which power lines can cause these sorts of cancer risks, and so it is not clear what you need to actually try to protect people from.
On top of this, the risks associated with power lines are exactly the sort that people don't understand, and so people's response to these risks is greatly exaggerated. Mommy who is scared of power lines will think nothing of dumping Bucko into an SUV and drive to the supermarket.
First question: what is the mechanism of the danger.
1) It _might_ be 'EMF's, the 60Hz changing electric or magnetic fields that are present in proximity to the power lines. Because power lines are pretty well balanced, these fields fall off rapidly as you move away from the power lines. Additionally, EMFs can be reduced by careful selection of phasing on adjacent power lines, moving conductors closer together, and probably several other techniques. Reducing 'loop area' is the best thing to do in order to reduce EMFs, but this means moving the conductors closer together, which in turn means much more difficult insulation systems.
On the other hand, the mechanism for injury by low order EMFs has _not_ be established, and in fact some studies suggest that the risk really is elsewhere. If I recall correctly, there was a study of telephone company employees which divided them into three groups with respect to intensity of EMF exposure. The interesting thing is that the _middle_ exposure group had the highest cancer risk.
2)It might be something well understood as a risk that is associated with power lines, but because people think 'power lines' they ignore that the problem is the associated risk. For example, PCB transformer fluids are well known to be a cancer risk. Perhaps the risk is _not_ with the electrical fields at all, but instead with the materials used to build the power distribution infrastructure. If the insulating materials are the risk, then moving the conductors closer together (to reduce EMF) will simply cost money and might _increase_ the health risk of the power lines.
3) Some 'unexpected' risk mechanism. My pet theory is that the power lines themselves are not a real risk, but that bad insulators on power lines, subject to corona discharge, can produce enough X-rays to cause a cancer risk. I've not followed up on this theory, nor even done the appropriate 'back of the envelope' calculation.
Just some thoughts.
Re: HV power line controversy continues#44164 10/29/0403:08 PM10/29/0403:08 PM
Also, separating out cause and effect can be difficult. It appears that they are assuming that an increase in cancer in the vicinity of a power line means that the fields around the power line caused the cancer. An alternative possibility is that real estate that close to a power line is undesireable, and therefore tends to host high-density, low-income housing. There are two problems with that: Low-income housing may tend to host populations that have habbits or backgrounds that tend to encourage cancer, and high density will of course produce a larger number of cases if the density is not accounted for.
[This message has been edited by SolarPowered (edited 10-29-2004).]
Re: HV power line controversy continues#44165 10/29/0406:39 PM10/29/0406:39 PM
About 10 years ago I assisted my then high school daughter with a science fair project titled: "EMF - Higher in Your Home or near Power Lines?" I borrowed a Gaussmeter from one of our power quality guys and we made lots of readings in our home and under various power lines and inside some substations. (I am an engineer with an electrical utility) By far the highest Gaussmeter readings were inside our own home. We made readings under 12kv, 46kv, 115kv, 230kv, and 500kv lines. The readings under any of the lines never exceeded about 20 mG. The highest reading I saw from any of the utility's equipment was about 2 meters from a 115kv bus in a substation near our home. That was about 200 mG. Of course this was an area not accessible to the public and I did not take my daughter inside the fence.
By contrast, holding the Gaussmeter near an electric can opener gave a reading over 1000 mG, about the same for an electric hair dryer. Electric range was about 50. Our home is not near any overhead power lines so all the fields are generated by electrical equipment in the house. All the readings I quote here are from memory since I have lost the file with all the data, but if anyone is interested I can find a paper copy and furnish it here.
As someone has mentioned, the intensity of the field drops off rapidly with distance. We did not measure electric fields, only magnetic.
Since I have worked near some very high voltage, high current equipment I am very interested in any proof that my health is in danger. So far I've seen nothing. I believe the whole issue is about money.
If you are truly concerned about the effects of magnetic fields, start cleaning up your home first. Don't sleep under an electric blanket. That was about 80 mG. Lots higher than you'll find under any power line of any voltage.
Re: HV power line controversy continues#44166 10/30/0403:01 PM10/30/0403:01 PM
An alternative possibility is that real estate that close to a power line is undesireable, and therefore tends to host high-density, low-income housing. There are two problems with that: Low-income housing may tend to host populations that have habbits or backgrounds that tend to encourage cancer, and high density will of course produce a larger number of cases if the density is not accounted for.
Good point. I often feel that many studies on various subjects are quick to zoom in on the one particular aspect being discussed, but fail to account for other variables which may have an equal or greater effect.
If you are truly concerned about the effects of magnetic fields, start cleaning up your home first.
Indeed. I recall a TV program here in Britain a couple of years ago discussing the powerline "problem" and visiting a house which had HV lines running right across the back. Gaussmeter readings around the head-end of the boy's bed went off the scale, and it was soon realized that the electric meter was right on the other side of the wall. He'd been getting a far hugher field strength from that than from the HV lines the family had been worrying about.
Re: HV power line controversy continues#44167 10/30/0404:40 PM10/30/0404:40 PM
There was a while back an interesting piece in the paper about a theory that the electrical charge near high voltage power lines can exert an attraction for certain particles; breathing in the relatively higher concentration of those may be connected with these reported illnesses more than any purely electrical or magnetic effect, which, as several people have pointed out, should be more-or-less self-cancelling.
The particles mentioned were certain pollutants from hydrocarbon incomplete combustion but also certain naturally ocurring alpha emitters such as radon gas were measured in higher amounts near the lines.
There has been no proper collection and analysis of data yet to measure the exact particle levels in these "illness cluster" areas, actually in people's dwellings and offices, but it certainly sounds like an promising theory, so those investigations will be interesting to read about.
Myself I did not like to live too close to them beacuse of the noise when it was damp or wet weather, fizzling and buzzing, and because of the disagreeable ozone smell, which is also, it is said, very bad for lungs.