Electromagnetic Fields 2015 Update
7. Extremely low frequency fields (ELF) like those from power lines and household appliances
- 7.1 What are the sources of ELF fields?
- 7.2 What is the level of exposure to ELF fields?
- 7.3 Can ELF fields increase the risk of childhood leukaemia and other cancers?
- 7.4 Can exposure to ELF cause headaches or other health effects?
- 7.5 Can ELF magnetic fields have effects on human reproduction?
- 7.6 What can be concluded about ELF fields?
7.1 What are the sources of ELF fields?
Power lines generate ELF fields Credit: Miguel Saavedra
In this assessment, extremely low frequency (ELF) fields
fields with frequencies below 300 Hz, the frequencies
that are lower than intermediate frequencies. The main source of
ELF is alternating current
carried in overhead lines of railways, power lines, electric
installations and household appliances. The
magnetic field generated
has the same frequency as the current that produces it, i.e.
16 2/3 Hz, 50Hz or 60Hz (the latter predominantly in
US). Additional important sources of ELF
magnetic fields include
power plants and substations, welding machines, induction
heaters and tramway and subway systems.
ELF fields can be electric or
- An electric
field is the created by
charges and characterised by forces acting upon other
electric charges. It is measured in volts per meter (V/m).
- A magnetic
field is created as a consequence of the
movement of electric charges
and characterised by the force acting upon resting or moving
electric charges. The strength of a magnetic field is
usually measured in ampere per meter (A/m), alternatively,
by accounting for the magnetic properties of material as
magnetic induction, in
The amplitude of both electric and
magnetic fields strongly
decreases with distance from the field source.
ELF electric fields tend to be strongest
below high voltage overhead
power lines (up to several kV/m), and ELF
fields are particularly strong near cables with high
current load such as at welding machines and induction furnaces
(up to a few mT). To determine compliance with exposure limits,
the maximum possible exposure next to the source must be
assessed, in general by comparing measured field quantities with
the given reference level. The maximum field level of
inhomogeneous fields next to a source may be several orders of
magnitudes higher than the reference level of equivalent
7.2 What is the level of exposure to ELF fields?
The general public can be exposed to
extremely low frequency (ELF) fields from various fixed sources
that are operative in our environment, such as power lines and
stations, in particular if those are placed inside
Passing directly below a high
line, exposure to
can be of several kV/m and to
of several 10 μT. The amplitude of electric and magnetic
fields decreases rapidly with increasing distance to the
At home, the magnetic
fields are strongest close to distribution boxes and to
household appliances in particular those, that contain motors,
consume high power such as electric ovens or heaters. The
smaller the dimension of a source, the more effective is
increasing distance in reducing field levels.
7.3 Can ELF fields increase the risk of childhood leukaemia and other cancers?
Studies on ELF MF are focusing on power frequency fields. In
2002, the International Agency for Research on
classified ELF magnetic
fields as “possibly
humans” (Group 2B). This was based on epidemiologic
studies that reported that children are more likely to develop
leukaemia if their
time-averaged exposure to ELF magnetic fields
exceeds 0.3-0.4 μT, which is relatively strong. Experimental
studies on animals did not support these findings. Furthermore,
the IARC concluded, there was no evidence for a link between
ELF magnetic fields and any other type of
This potential link between ELF fields and childhood
leukaemia has been
further addressed by a number of
which confirm an increased risk of leukaemia in children living
close to high voltage power
lines with estimated daily average exposures (above 0.3 to 0.4
µT) much higher than average
magnetic field exposure
But it remains difficult to judge whether this apparently
quite robust association is likely to be causal or a result of
methodological shortcomings of the studies such as information
bias, selection bias and
Indeed, little progress has been made in verifying the
causality of the reported association or in explaining the
finding, neither by a plausible mechanism nor in identifying an
alternative explanation. Besides, a large and more recent study
leukaemia survival in
relation to ELF magnetic
field exposure did not observe an association, adding no
support to the hypothesis that ELF
magnetic field may
promote pre-leukemic clones both related to the risk of
developing leukaemia as well as the risk of a relapse of
leukaemia after successful treatment.
Studies on other childhood
cancers or adult
cancers showed no consistent association and no new influential
study has appeared over the last few years concerning any other
type of cancer.
7.4 Can exposure to ELF cause headaches or other health effects?
As in the case of radio frequency fields, self-reported
hypersensitivity” is an issue that also comes up in
the case of ELF field exposure including reports on a variety of
symptoms such as skin redness, tingling and burning sensations,
as well as fatigue, headache, concentration difficulties,
nausea, and heart palpitations. There were several studies added
to the existing pool of investigations. Overall, the studies do
not provide convincing evidence for a causal relationship
between ELF MF exposure and self-reported symptoms.
Studies investigating possible effects of ELF MF exposure on
brain activity are too heterogeneous to draw a sound conclusion.
Largely consistent with earlier results, recent studies have
reported that exposure to ELF MF has no effect on activity or
locomotion. There is some evidence from animal studies that
exposure to ELF magnetic
fields may affect the performance of spatial memory tasks
(both deficits and improvements have been reported) and engender
subtle increases in behavioural anxiety and stress.
Other studies have investigated potential molecular and
mechanisms, and despite a number of studies continue to report
candidate mechanisms, particularly regarding effects on reactive
oxygen species, none has been firmly identified that operates at
exposure levels found in the everyday environment.
do not provide convincing evidence of an increased risk of
neurodegenerative diseases, including dementia, related to power
frequency MF exposure.
7.5 Can ELF magnetic fields have effects on human reproduction?
showed no evidence for adverse effects on pregnancy or on the
health of the children. Some studies report some implausible
effects but need to be replicated independently, before they can
be used for risk
7.6 What can be concluded about ELF fields?
The new epidemiological
studies are consistent with earlier findings of an
increased risk of childhood
estimated daily average exposures above 0.3 to 0.4 µT. As stated
in the previous Opinions, no mechanisms have been identified and
no experimental studies have been able explain these findings,
which, together with shortcomings of the
prevent a causal interpretation.
Overall, existing studies do not provide convincing evidence
for a causal relationship between ELF MF exposure and
Studies investigating possible effects of ELF exposure on the
power spectra of the waking EEG are too heterogeneous with
regard to applied fields, duration of exposure, number of
considered leads and statistical methods to draw a sound
conclusion. The same is true for behavioural outcomes and
do not provide convincing evidence of an increased risk of
neurodegenerative diseases, including dementia, related to ELF
MF exposure. Furthermore, they show no evidence for adverse
in relation to ELF MF. The studies concerning childhood health
outcomes in relation to maternal residential ELF MF exposure
during pregnancy involve some methodological issues that need to
be addressed. They report implausible effects but need to be
replicated independently before they can be used for
Recent results do not show that ELF fields have any effect on
the reproductive function in humans.