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IS there any merit in the argument that living in proximity to power lines could be injurious to health? The Government, through the Director of Health, proclaims there is no conclusive evidence of any such risk. There are three aspects of this comment I wish to consider.

First, is this a correct criterion? There is no conclusive evidence that the majority of people in Hong Kong want democracy. Yet we act on the assumption that they do. Likewise, there is no conclusive evidence that vitamin C cures colds, or that ingestion of fat necessarily leads to high cholesterol, or that there can be ill effects from the radiation from computer screens. Yet many hold such beliefs and act accordingly. Conclusive evidence in fact is not the main criterion for action, but rather whether a majority or strong enough lobby exists.

Second, What conclusive evidence do we have? We know that every alternating electric current produces a magnetic field around it. When two cables carrying a current are close, as in household wiring or appliances, the two effects tend to cancel, but from high capacity cables widely spaced, as in high voltage power lines, the magnetic field can be detected at considerable distance. Alternating magnetic fields induce electric currents in conductors they cross - the transformer effect. So there is absolutely conclusive evidence that people in proximity to power lines will have, normally tiny, electric currents induced in their nervous systems and conduction channels in their brains. The Director of Health refers to the absence of conclusive evidence that would prove such tiny currents affect health in all people. Almost certainly they don't.

Third, are there exceptions? There are certainly two, related to mind and sensitivity. Consider the power of the mind over health. There is conclusive evidence that people who become convinced they will be healed or struck by a disorder often will be. There is evidence, though not conclusive, that cancer is one such disorder. Thus, after all the publicity given to the possibility of a health hazard from power lines, specifically to the speculated possibility of cancer or more specifically leukaemia, someone is going to convince themselves of the likelihood that they will get sick. This will be the fault of not so much the power lines as the furore they have generated. But the fact is the furore has been created and the hazard established. So if the power lines are put up in the face of such a furore there probably will be, at least, a first generation health hazard - albeit for the wrong reason.

Next is the question of sensitivity. Extensive tests have been carried out to see if some people are more sensitive to magnetic fields than others. There is now strong evidence that some are. They may be a small minority, but they do exist. They exhibit symptoms such as headaches, tiredness, loss of concentration. You could regard such effects as analogous to an allergy, to which only a few people are prone. Effects related to cancer have been observed in the laboratory.

My conclusions are twofold. First, it would seem that because of the way the present problem has been handled there is little choice but to make some concession to the affected residents. The lesson to be learned for the future is to be much more open in any similar project and to make sure anyone likely to object is given every opportunity to do so.

Furthermore, any false or exaggerated information on possible health hazards should be exposed before any plans are finalised. Second, government has a responsibility to obtain all the evidence available from the numerous studies regarding minority sensitivity to alternating magnetic fields and to determine the proportion likely to be affected, however tiny. If the present routeing of the power lines goes ahead, it should relocate the household of any resident who has been affected. This is initially only likely to be discomfort rather than cancer.

I believe the chances of this happening to be remote, but such action would enable the Government to be seen to show real concern and care for its citizens, not apparent in its existing policy of requiring conclusive evidence in this particular case before it acts.