Increasing the tension

To be honest, I'm not quite sure why I'm posting this. Probably because it relates to a debate I used to have with people I worked with.

The Independent (UK) has reported on another study that has indicated a relationship between living close to high-tension power lines and the risk of developing childhood leukemia.

Although this is not the first such report, the idea is still quite controversial, largely because no one knows a mechanism by which the power lines could be connected to the development of the disease. But I have to admit that I find the consistency of the results - which tend, as this one did, to find a "small but statistically significant" effect - pretty persuasive. The article notes four other such studies:

* Swedish study finds threefold increased risk of childhood leukaemia in families living within 50 metres of power lines.

* Canadian study finds 80 per cent increased risk for children within 100 metres of lines.

* Analysis of nine studies finds doubling of childhood leukaemia in families exposed to magnetic fields of 0.4 microteslas (within 60 metres).

* International Agency for Cancer Research classifies extremely low frequency magnetic fields as "possibly carcinogenic".

The study here, led by Gerald Draper of the Childhood Cancer Research Group at the University of Oxford, was published in the British Medical Journal. It considered 10,000 cases in England and Wales over 33 years and found that children living within 200 meters (about 650 feet) of high-voltage lines had a 70% increased risk of leukemia, while those living 200-600 meters (about 650-2000 feet) away had a 23% increased risk. The latter figure can easily be dismissed as a statistical artifact - i.e., coincidence - but it's much harder to do that with the former.

Not impossible, though: Because we're talking about portions of portions of populations, the actual numbers are still small. The increase in the number of cases of leukemia per year in England and Wales predicted by these results is about five out of 420, an increased incidence of about 1.2%. Not insignificant to those five children and their families, but still it could be coincidence.

Then there is still the matter of how living near power lines would connect to leukemia. The only suggestion the article mentions is the possibility that particles of air pollution near the lines could become electrically charged, making them more likely to get stuck in the lungs once inhaled. While that's plausible, it leaves open the question of what the link between that and blood cancers would be. Meanwhile, others have other ideas:

John Swanson, scientific adviser to National Grid Transco and a co-author of the study, said: "The findings strongly suggest something is happening but leave open what that something is. I personally tend to the view that it is some characteristic of the populations that the power lines pass through."

The fact that he's an adviser to the outfit that owns the high-voltage power lines in question should give us pause, but the demographics of an affected population is one of the things that researchers have to consider.

Still, it seems to me that there's an eagerness to acquit the power lines that leads some, such as Swanson, to engage in speculation and others to say things that are just odd:

An editorial in the BMJ says magnetic fields generated by Britain's 4,500 miles of power lines are very weak, amounting to 1 per cent of the Earth's magnetic field "which affects all of us all the time. So it would be surprising if they caused leukaemia," it adds.

Frankly, that argument just doesn't make sense. First, it's disturbingly similar in form to the hoary arguments for the supposed safety of nuclear power: Oh, you get more radiation from the Sun or from living in a stone house or from a chest X-ray, so stop your whining, you big wuss.

Second, the concern is not that power lines cause leukemia, it's that living near them makes it, for some reason, more likely a child would get leukemia. As a comparison, consider someone saying we shouldn't be concerned with AIDS because people rarely die of it, instead they die of some opportunistic infection like pneumonia - "and AIDS doesn't cause pneumonia." No, it doesn't. But it does make it more likely you'll catch it and more likely to die of it if you do.

Third, on a more I guess philosophical level, why is it apparently considered impossible that the natural environment could be damaging to some small portion of the population? No, evolution, which works on populations as a whole and does not affect every individual member in exactly the same way, does not rule that out: Consider that there are people who are allergic to sunshine and that exposure to the Sun is related to developing malignant melanoma. How much more natural and necessary to life can you get than sunlight? But that doesn't make it harmless in all persons. What I'm arguing here is that isn't it possible that by whatever mechanism, the Earth's magnetic field increases the risk of leukemia in some persons? Could it in fact be related to the incidence of the disease? If so, living near high-power lines, exposed to some small additional magnetic fields, might well be responsible for some small increase in leukemia cases.

Note carefully that I'm not saying that magnetic fields, either natural or from power lines, are responsible for cases of leukemia. What I'm saying is that unless a connection between magnetic fields and leukemia has been ruled out, which it apparently hasn't, BMJ's argument doesn't scan.

Still, we have to come to some kind of at least temporary bottom line here and I still keep coming back to what I used to tell people who asked me about it (which they did because of where I was working at the time): The effect is, again, statistically significant, but it's small. So my advice is, if you don't have to live near a power line, don't. But if you do wind up living near one, don't spend a lot of time worrying and stressing over it: That very likely would be worse for your general health than the power lines are.