There have been no specific epidemiological studies to look for health effects of corona ion emission from powerlines but two scientific publications arising from the UK Childhood Cancer Study (UKCCS) found evidence of increased rates of childhood leukaemia in populations living in the vicinity of high voltage powerlines in the UK.
The continuing research studies by Professor Henshaw's team confirm that most powerlines emit corona ions and in some cases this is a severe effect. Their previous findings emphasised the importance of the attachment of the electrically charged corona ions to small particles of air pollution, resulting in these particles having higher electric charge so that when inhaled they had a higher probability of depositing in the lung.
However, Professor Henshaw's team is now finding that corona ions themselves are able to create new particles of air pollution, by attracting gaseous pollution molecules in the air. The particles that are created are extremely small and fall into a class of so-called nano-particles or nano-aerosols. There is currently a debate about the possible adverse health effects of inhaling nano-particles since these are capable of penetrating deeply into the lung and passing into the bloodstream. Nano-particles created by corona ions by their nature contain electric charge and these would be expected to be even more likely to deposit in the lung.
The Bristol team stands by its existing estimates of the potential health effects of corona ion emission from high voltage powerlines. In a paper published in the journal Medical Hypotheses in 2002, Professor Henshaw estimated that as a result of corona ion emission, 200 to 400 additional cases of lung cancer, 2,000 to 3,000 additional cases of other illnesses associated with air pollution and two to six additional cases of childhood leukaemia may occur each year in populations living near high voltage powerlines in the UK.
Professor Henshaw said: "Although the risk to the individual is relatively small, in terms of public health policy these estimates should be taken seriously. My view is that powerlines should not be erected near populated areas in the UK."
Information on childhood leukaemia and magnetic fields may be found at www.electric-fields.bris.ac.uk
There have been no specific epidemiological studies to look for adverse health effects that may be attributed to corona ion emission from powerlines. Some studies, however, have made some interesting findings:
1. The UK Childhood Cancer Study published in The Lancet in 1999 (The Lancet, 254, 1925-1931, 1999) found that more cases of childhood leukaemia compared with control cases live near powerlines. This was statistically significant. The observation was not related to the measured magnetic fields, which suggests there may be some other feature of living near high voltage powerlines resulting in increased risk of leukaemia.
2. The UK Childhood Cancer Study published in the British Journal of Cancer in 2000 (British Journal of Cancer, 83, 1573-1580, 2000) made a partial test of corona ion effects by asking whether or not childhood leukaemia cases were more likely to live within 400 metres of National Grid 275 kV and 400 kV powerlines. They found that this was more likely, with 42% more cases living near powerlines compared with away from powerlines. However, this result just fell short of statistical significance (the odds ratio was 1.42: 95% CI 0.85 - 2.37).
3. Studies in South West England by Professor Alan Preece and his team in the Department of Oncology at Bristol Royal Infirmary found increased incidence of both lung cancer and mouth cancer in populations living downwind of powerlines with respect to the prevailing south-westerly wind in South West England. Lung cancer rates were 25% higher downwind compared with upwind. This was statistically significant.
4. Professor Henshaw's estimates of the number of cases of ill health in those living near high voltage powerlines in the UK were published in Medical Hypotheses in 2002 (Medical Hypotheses, Vol. 59 (1), 39-51, 2002).