Both “New Scientist” and “The Independent” have interesting articles on the Draper study which takes a more cautions look at the findings. Draper seems to be backing off from his study findings by making the usual old disclamers that have used to discount positive findings in EMF epidemiological studies ever since Wertheimer & Leeper’s 1970s Denver study. We even see the old misleading comparison to the earth’s static magnetic field which cannot be compared to an oscillating power frequency field as they are totally different. Whatever is the cause for the observed increase in childhood cancer the closer one is to high voltage transmission lines one cannot simply dismiss it as a statistical fluke.
For example, a New Zealand study that looked at ill health in proximity to transmission lines in Auchkland NZ found an increase in chronic health states the closer people lived to the lines.
The problem for the Draper study is that, even though no magnetic field readings were taken, at the distances used in the study, the magnetic field emissions from the lines would have been too low to have an effect.
Note where Draper and his power company associates apparently consider the possibility of giving 5 kids leukaemia from high voltage powerlines annually is of “no cause for concern”. I wonder what the UK charity “Children with Leukaemia” think of that one?
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Large study links power lines to childhood cancer
00:01 03 June 2005
NewScientist.com news service
Children living near overhead power lines may have an increased risk of leukemia but the association may not be causal, UK researchers say.
The confusing message, which comes from the largest study to date – of over 29,000 children with cancer – is that since “there is no biological mechanism to explain the higher risk”, the results, “although statistically significant, may be due to chance”.
The study, a collaborationbetween the Childhood Cancer Research Group at the University of Oxford and National Grid owners, Transco – looked at cancer data in England and Wales between 1962 and 1995, for children aged up to 15 years old.
They were able to map how far each child lived from a high voltage overhead power line. Comparing the children who had cancer with a control group of 29,000 children without cancer but who lived in comparable districts, found that children whose birth address was within 200 metres of an overhead power line had a 70% increased risk of leukemia. Children living 200 to 600 m away from power lines had a 20% increased risk.
“To put these results in perspective, our study shows that about five of the 400 cases of childhood leukemia every year may be linked to power lines – which is about 1% of cases,” says Gerald Draper at Oxford University, who led the study. “The condition is very rare and people living near power lines should have no cause for concern.”
However, the results are controversial, coming just one month after the major UK Childhood Cancer Study report, which declared that there was no risk to children living these distances away from power lines.
Although a link between childhood cancer and power lines has been suggested by previous studies, it has only been associated with high exposure – those living within about 60 m of an overhead power line. At the distances Draper looked at, the electromagnetic field created by the power lines should be too low to have any health effects, he says. They were much lower, for example, than those constantly experienced due to the Earth’s magnetic field.
“We don’t think it is possible that a magnetic field of these low magnitudes could have a causative effect on childhood leukemia,” Draper says.
The increase in leukemia risk for those living at distances greater than 60 m was “difficult to interpret, but is most unlikely to be due to any residual electromagnetic field, or other exposures related to the power line”, says David Grant, scientific director of Leukemia Research. “It cannot be excluded that it is a statistical artefact.”
But given the statistical significance of their results, the researchers had considered other theories. One established link with the disease is low exposure to infection soon after birth – an effect seen most commonly in babies born to higher income, middle-class families, where early social mixing between infants is rarer.
Draper’s group looked at the population characteristics in areas immediately surrounding power lines. They found that some were built in areas of low income housing and others in high-income areas. Looking at social status data alone, there was a 10% increase in leukemia for those in middle-class families, but these results were found to be independent of power line location data.
Another theory that the researchers tested, first mooted controversially in 1999 by Dennis Henshaw at Bristol University, UK, concerned “corona ion” effects. Henshaw proposed that the air immediately surrounding a high voltage power line or pylon becomes ionised by the electric field.
Corona ions combine with pollutants in the air, giving rise to charged airborne particles, which may be blown some distance away before being inhaled. Henshaw believes that once breathed in, the particles remain in the lungs, causing cancer.
The researchers attempted to test this theory with Henshaw, and found no discernable difference between leukemia cases upwind or downwind of the power cables. However, they admit that the testing procedure, although the best available at the time, was poor. They are preparing to conduct a more conclusive test, with Henshaw’s newly devised equipment. He believes the excess number of children found to have leukemia due to power lines – five per year – “may be the tip of the iceberg”.
This paper forms part of Draper’s larger study, which is also looking at electromagnetic doses at different distances from power lines.
Journal reference: British Medical Journal (vol 330, p 1290)
Fears over Child Leukemia Link to Power Lines
By Jeremy Laurance
The Independent UK
Friday 03 June 2005
Public concern about the safety of high voltage power lines will be heightened today by a study showing children living within 200 metres of the overhead electricity cables have a 70 per cent increased risk of developing leukaemia.
The study, involving almost 10,000 cases over 33 years, found the effect was small but statistically significant. There was also an effect on children living between 200 and 600 metres from the power lines who had a 23 per cent increased risk of leukaemia.
However, the researchers, led by Gerald Draper of the Childhood Cancer Research Group at the University of Oxford, were unable to offer any explanation for their findings, published in today’s British Medical Journal. They ruled out electro-magnetic fields produced by the power lines as a cause as they would be too small to have any effect at a distance of 200 to 600 metres. About one child in 2,000 develops leukaemia before the age of 15 and about 4 per cent of the population live within 600 metres of power lines. Overall, the researchers estimate that proximity to the overhead cables may account for five of the 400-420 cases of childhood leukaemia occuring in England and Wales each year.
Dr. Draper said: “These results are very surprising. Although previous studies have suggested some increase [in the risk of leukaemia] you have to be much nearer [within 60m]. No one would expect an effect at this distance.
“We don’t think this is a direct effect of the magnetic field at 200 to 600 metres. There might be some other indirect, remote mechanism that we don’t understand and we can’t measure. Or the findings might be due to chance.”
It was possible some characteristic of the populations who lived near the power lines, or of the area where they were situated, could account for the increase in leukaemia. The disease is 10 per cent more common in better-off families and varies by geographical area.
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.”
Another hypothesis is that pollutants in the air around power lines could become electrically charged, making them more likely to lodge in the lungs.
Dr. Swanson said the failure of the UK Childhood Cancer Study to find any effect of power lines could be because it was too small.
Both authors said that there were no grounds for taking any action such as moving house on the basis of their results.
Dr. Draper said the study, begun in 1997, was incomplete because the researchers had not measured the size of the magnetic field generated by the power lines and compared it with that from other sources. He said that he and his fellow researchers had decided to publish early after an environmental group accused them of suppressing the findings and leaked some details of the research last year. 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.
Professor John Toy, the medical director of Cancer Research UK, said: “People who live or have lived near power lines need not panic about this research.
“The triggers that cause childhood leukaemia are most likely a random course of events over which a parent has no control,” he added.
* 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”.
* UK Childhood Cancer Study concludes electromagnetic fields “are not principal causes, if at all, of leukaemia in children.”
* Oxford Children’s cancer group concludes living within 600 metres of lines could account for five cases of leukaemia a year.Leave a reply →