Sir, - Dick Ahlstrom's article in your edition of September 22nd, apparently written before the broadcasting of last Thursday's BBC Radio 4 programme Costing the Earth, fails to convey the seriousness of our power line measurements or of the legitimate public concern of reports of ill health in living near power lines. The behaviour of ionised particles emitted from high-voltage lines ("corona ions", which are also responsible for the familiar sizzling noise from power lines) was first established in the 1950s. In the 1980s, extensive investigations in America were carried out into corona ion behaviour in the atmosphere using high-voltage test lines. The findings were published in power transmission industry journals.
The period of scientific peer review of these extensive measurements has long passed and we are now in the realm of established, albeit specialised, knowledge. (It should be emphasised that the radon measurements near power lines by Dr McLaughlin to which Dick Ahlstrom refers have nothing to do with corona ions or how they attach to particles of existing pollution in the air, thereby increasing their lung retention on inhalation.)
Our work published last December illustrates the extent of corona ion emission from today's power lines. The measurements used well-established, albeit sophisticated, measuring equipment. These measurements demonstrate both how increased exposure to air pollution occurs, as well as indicating the likely level of this increase. Increased exposure implies increased risk of those illnesses known to be associated with air pollution.
Dr Alan Preece of Bristol presented some data on cancer rates in adults near power lines at a conference in Munich last June. Scientific conferences are the right and proper place to present new ideas and preliminary data. It so happened that several journalists also attended the conference and noted Dr Preece's preliminary findings, as did a representative from the Irish Department of Health. Those findings leaked out in last Thursday's BBC programme. That they did not do so earlier is perhaps surprising. This leak of an unfinished and unpublished investigation may in hindsight serve to underline why a priori we are concerned about the public health implications of our measurements. It may also serve to illustrate why legitimate public concern at perceived increases in cancer incidence near power lines, notably in Mr William Hague's Yorkshire constituency as voiced in the BBC programme, warrants investigation.
Surprising though it may be, the effects on public health of corona ions has not been investigated before. Their intensity near some power lines, which has surprised even ourselves, has public health implications, as well as implications for the siting of power lines anywhere near populated areas, even if at all above ground. An informed public debate is called for. - Yours, etc.,
Prof Denis L. Henshaw, H. H. Wills, Physics Laboratory, University of Bristol, England.