Intended for healthcare professionals

Rapid response to:

Papers

Childhood cancer in relation to distance from high voltage power lines in England and Wales: a case-control study

BMJ 2005; 330 doi: https://doi.org/10.1136/bmj.330.7503.1290 (Published 02 June 2005) Cite this as: BMJ 2005;330:1290

Rapid Response:

Draper et al's findings may have a causal origin

The finding of increased incidence of childhood leukaemia by birth
address up to 600 metres from high voltage powerlines may have a causal
origin in terms of both the associated electric and magnetic fields.

A plausible explanation for the approximate 70% increased incidence
in childhood leukaemia up to 200 metres from powerlines may be via the
disruption in the body of the hormone melatonin. Russ Reiter of the
University of Texas and I have just completed a review of this topic as
part of last June's World Health Organisation meeting on EMF and Child
Health held in Istanbul. Our review of 14 international studies in human
populations are consistent in indicating that magnetic fields down to 0.2
microtesla or lower can suppress the nocturnal production of melatonin in
the pineal gland. Melatonin is a powerful antioxidant which acts as a
natural anti-cancer agent. The hormone has been shown to be highly
protective of oxidative damage to human blood cells. In animals,
melatonin has been shown to be highly protective of oxidative damage to
the fetus, the site where initial leukaemic damage is believed to occur in
children. Leukaemia has been induced in mice exposed to constant light,
which also has the effect of suppressing nocturnal pineal melatonin. Full
details of our review may be found on our website below.

At Bristol, we are also researching the effects of corona ion
emission from high voltage powerlines. These ions can be carried hundreds
of metres from powerlines by the wind (they have been detected up to 7 km
away) and this could explain the observed increased childhood leukaemia up
to 600 metres from powerlines. Corona ions are produced by the ionisation
of the air under the intense electric field on the surface of powerline
cables. Once emitted into the atmosphere, corona ions attach themselves
to particles of air pollution thereby increasing the electric charge on
such particles. At ground level, when subsequently inhaled, these charged
pollutants then have a much higher probability of becoming trapped in the
lung by mirror-charge (static electricity) effects. We are particularly
interested in pollutant particles in the approximate size range 20 - 300
nanometres since these predominantly contain the potentially carcinogenic
polycyclic aromatic hydrocarbons (PAHs). Once in the lung, such particles
would readily pass into the bloodstream. Ambient exposures to PAHs have
been shown to produce heritable mutations in mice. In figure 3 of Fews et
al 1999 we demonstrate that corona effects are prominent at 600 metres
even from 132 kV powerlines which were not those mainly considered in the
Draper et al study. The National Radiological Protection Board's report
on corona ions concedes the plausibility of the above proposed scenario.
There is substantial mechanistic evidence to suggest that air pollution is
a causal factor in the incidence of childhood leukaemia. The ubiquitous
nature of air pollution exposure is such that a link with childhood
leukaemia has been difficult to demonstrate in an epidemiological study
with case-control design. However, increased childhood leukaemia in
relation to pollution hazard sites in the UK has been reported.

Overall, the distance profile of childhood leukaemia rates observed
by Draper et al could be fitted by a model comprising the fall-off of
magnetic fields within 200 metres of powerlines and the continuing
presence of corona ion effects up to 600 metres away.

Full details of these scenarios may be found via our response
statement to the Gerald Draper et al study at www.electric-fields.bris.ac.uk

Key references

1. Henshaw D L and Reiter R J, 2005. Do magnetic fields cause
increased risk of childhood leukaemia via melatonin disruption?
Bioelectromagnetics (In Press).

2. Henshaw D L, 2002. Does our electricity distribution system pose
a serious risk to public health? Medical Hypothesis, 59,39-51.

3. Fews A P, Henshaw D L, Wilding R J & Keitch P A, 1999.
Corona ions from powerlines and increased exposure to pollutant aerosols.
Int. J. Radiat. Biol, 75 (12), 1523-1531.

4. National Radiological Protection Board. Particle deposition in
the vicinity of power lines and possible effects on health. Documents of
the NRPB 2004, 15(1).

Competing interests:
None declared

Competing interests: No competing interests

07 June 2005
Denis L Henshaw
Professor of Human Radiation Effects
H H Wills Physics Lab, University of Bristol, Tyndall Ave, Bristol, BS8 1TL