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Power lines and cancer
Power
lines produce extremely low frequency (ELF) electromagnetic
fields in range of 50 Hz to 60 Hz. Electric fields do not
reach people inside houses, but magnetic fields go through
most materials and cause an additional exposure higher than
the typical background field (about 0.1 µT)
up to a distance roughly 50 metres from the power line, depending
on the voltage and wire configuration. Health effects on humans
related to this non-ionising type of radiation have been investigated
in epidemiological studies for over two decades.
The
first report of an association between childhood cancer and
power line exposure was published in 1979, and after that
at least 24 studies on the same topic have been published.
There have been two meta-analyses published lately that both
suggest a significant 1.7–2.0-fold excess of childhood
leukaemia in the extremely rarely existing fields above 0.3
or 0.4 µT.
The excess may be attributable to patient selection and publication
bias, and a plausible biological mechanism is not known.
It appears on the basis of studies
with large numbers of cancer
cases that there is no excess risk of cancer among adults
living
close to power lines, but the possibility of an association
between
some cancers and exposures to ELF magnetic fields is suggested
by some occupational studies.
IARC
classified ELF magnetic fields as possibly carcinogenic to
humans (Group 2B) in its evaluation [14],
while ELF electric fields were considered not to be classifiable
as to their carcinogenicity to humans (Group 3). This evaluation
only considers the likelihood of an association, but does
not take into account the magnitude of the possible risk to
individuals nor the population attributable risk. The results
of epidemiological studies suggest that appreciable magnetic
field effects, if any, are concentrated among relatively high
and uncommon exposures.
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