Sumimasen: > Wireless World magazine had a good analysis of the analysis > back in the late '80s when this was a really hot topic. > > It's not the EM that is the problem. It's the way the > magnetic field ends up concentrating cosmic rays > under the power lines. Think cylindrical lens. > Detection rates for cosmic rays were several times > higher under the power lines and lower in the region > immediately outside the towers. Alas, it's not that simple. I've been watching this area for several decades and noting the numerous studies which "prove things conclusively" from both sides. There is NO single mechanism that does a good job of providing a plausible explanation and few results, positive or negative, which stand up to intensive scrutiny or repeatability. IF there is an EM fields related damage mechanism, or a number of them, they are close to being down in the noise. That doesn't mean they should be dismissed or not looked for. An effect may cause substantial damage and even loss of life and be hard to detect because it ony occurs in selected environments. Saving perhaps hundreds of lives a year MAY be cheap and easy if you can ever determine what the effect is. I posted this study because it was by a reputable organisation and had a large user base and seemed well enough designed and targeted to be worth thinking about. They note that while they believe theeffect to be real they do not know the mechanism and note that it may be due to confounding factors. "Above all, do no harm" should be as much a requirement of our profession as for others. AFAIR the cosmic ray lensing effect, which seemed to offer a very nice explanation of the problem, did not stand up to extended scrutiny. If this mechanism is a real one then it would be a very good explanation of how non-ionising ratiation can cause cell destruction. The fact that this theory was well known and that areas along either side of transmission lines are now not bare earth suggests that the theory failed the test of full investigation. Even vested intetest from power utilities only foes so far. > I always get a little peeved when people complain > about EM from power grids. The nerve cells in our bodies > have membranes that are tiny (u inches) and voltages that > are small(10's or 100's of mV (nerve/muscle)) but > work out to 10's to 100's of KILOVOLTS per meter. > Compared to what our body is generating internally, > external EM is buried in the noise. If it weren't > we'd all be twitching whenever our cell phones were > operating. The *mechanism* is not important. It's whether there *is* a correlation. If we classify things which we don't understand to the same category as the waving of dead fish, because we haven't enough imagination or luck to ascertain the mechanism we may miss out badly. Explaining how something doesn't work has little point if it does achieve the tesult by some other means. In a related field: In Sellafield / Windscale there have been a number of concentrations of childhood cancer very significantly in excess of the statistically expected average and dissimilar to what is seen anywhere else in the UK. Careful radiation studies have shown that there have been no increased radiation levels or other factors relating to the town's nuclear fuel reprocessing plant. so it is clear that these are just "bad luck" and they don't need to look further into the safety issues at the reprocessing plant. If you believe that line you can probably get a nice job at the plant and assisted passage, along with your family. RM > > On a similar vein, some 1980's study found that women who > used electric blankets had higher rates of miscarriage. > Of course the authors forgot to check on whether > being hot while you slept was a contributing factor. > A later study found that sleep temperature had a stronger > correlation. But by then the damage had been done and > manufactures had to produce 'low emission' electric > blankets. (just have the heating wire double back on > itself so that the magnetic fields canceled. > > Just my few billion electrons worth. > > Robert > (who works in Neuroscience, so I've been well overexposed > to the details. e.g. trying to record tiny nerve signals > which are swamped by muscle electrical signals). > > Russell McMahon wrote: > >> Sometimes y' just gotta do it regardless. >> Annoying but ... >> >> Study of 29,081 English/Welsh children with cancer incl 9,700 with >> Leukaemia to check correlation with distance from power lines at >> time of birth. >> >> Significant risk factor increase (1.69 times) found for children >> living withing 100 metres of power lines. >> >> British Medical Journal. >> >> >> http://bmj.bmjjournals.com/cgi/content/full/330/7503/1290?ehom >> >> The publication of this study has been long delayed. It was >> originally funded by a power industry source. Reasons for late >> release are not known with certainty. >> >> Do note that mechanism involved is not claimed to be known and the >> result *may* be due to 'confounding factors'. >> >> >> >> RM >> _______________________________________ >> >> EXCERPTS >> >> >> RESULTS >> >> Results Compared with those who lived > 600 m from a line at birth, >> children who lived within 200 m had a relative risk of leukaemia of >> 1.69 (95% confidence interval 1.13 to 2.53); those born between 200 >> and 600 m had a relative risk of 1.23 (1.02 to 1.49). There was a >> significant (P < 0.01) trend in risk in relation to the reciprocal >> of distance from the line. No excess risk in relation to proximity >> to lines was found for other childhood cancers. >> >> What this study adds >> >> A UK study of 29 000 cases of childhood cancer, including 9700 >> cases of leukaemia, found a raised risk of childhood leukaemia in >> children who lived within 200 m of high voltage lines at birth >> compared with those who lived beyond 600m (relative risk 1.7) >> >> Conclusions >> >> There is an association between childhood leukaemia and proximity >> of home address at birth to high voltage power lines, and the >> apparent risk extends to a greater distance than would have been >> expected from previous studies. About 4% of children in England and >> Wales live within 600 m of high voltage lines at birth. If the >> association is causal, about 1% of childhood leukaemia in England >> and Wales would be attributable to these lines, though this >> estimate has considerable statistical uncertainty. There is no >> accepted biological mechanism to explain the epidemiological >> results; indeed, the relation may be due to chance or confounding. >> There was also a slightly increased risk for those living 200-600 m >> from the lines at birth (relative risk 1.2, P for trend < 0.01); as >> this is further than can readily be explained by magnetic fields it >> may be due to other aetiological factors associated with power >> lines >> ___________________________ >> >> >> Childhood cancer in relation to distance from high voltage power >> lines in England and Wales: a case-control study >> Gerald Draper, honorary senior research fellow1, Tim Vincent, >> research officer1, Mary E Kroll, statistician1, John Swanson, >> scientific adviser2 >> 1 Childhood Cancer Research Group, University of Oxford, Oxford OX2 >> 6HJ, 2 National Grid Transco plc, London WC2N 5EH >> Correspondence to: G J Draper gerald.draper@ccrg.ox.ac.uk > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > No virus found in this incoming message. > Checked by AVG Anti-Virus. > Version: 7.0.323 / Virus Database: 267.8.0/27 - Release Date: > 23/06/2005 > > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist