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Electromagnetic fields
and public health: extremely low frequency (ELF)
continuation from "ADR Protect" page
Below some data from the World Health Organization WHO - it is
interesting that WHO is taking time out their busy schedule to produce
REPORT on EMF, ELF..
.......While
the enormous benefits of using electricity in everyday life and health
care are unquestioned, during the past 20 years the general public has
become increasingly concerned about potential adverse health effects of
exposure to electric and magnetic fields at extremely low frequencies
(ELF). Such exposures arise mainly from the transmission and use
of electrical energy at the power frequencies of 50/60 Hz.
The
World Health Organization (WHO) is addressing the associated health
issues through the International Electromagnetic Fields Project......read
more
...The purpose of this Fact Sheet is to provide information about ELF
field exposure and its possible impacts on health within the community
and the workplace. Information comes from a WHO review of this subject
and other recent reviews by eminent authorities.
...
Sources
Naturally occurring 50/60 Hz
electric and magnetic field levels are extremely low; of the order of
0.0001 V/m, and 0.00001 µT respectively. Human exposure to ELF fields
is primarily associated with the generation, transmission and use of
electrical energy. Sources and typical upper limits of ELF fields found
in the community, home and workplace are given below.
Community:
Electrical energy from generating stations is distributed to communities
via high voltage transmission lines. Transformers are used to lower the
voltage for connections to residential distribution lines that deliver
the energy to homes. Electric and magnetic fields underneath overhead
transmission lines may be as high as 12 kV/m and 30 µT respectively.
Around generating stations and substations, electric fields up to 16
kV/m and magnetic fields up to 270 µT may be found.
Home:
Electric and magnetic fields in homes depend on many factors, including
the distance from local power lines, the number and type of electrical
appliances in use in the home, and the configuration and position of
household electrical wiring. Electric fields around most household
appliances and equipment typically do not exceed 500 V/m and magnetic
fields typically do not exceed 150 µT. In both cases, field levels may
be substantially greater at small distances but they do decrease rapidly
with distance.
Workplace:
Electric and magnetic fields exist around electrical equipment and
wiring throughout industry. Workers who maintain transmission and
distribution lines may be exposed to very large electric and magnetic
fields. Within generating stations and substations electric fields in
excess of 25 kV/m and magnetic fields in excess of 2 mT may be found.
Welders can be subjected to magnetic field exposures as high as 130 mT.
Near induction furnaces and industrial electrolytic cells magnetic
fields can be as high as 50 mT. Office workers are exposed to very much
smaller fields when using equipment such as photocopying machines and
video display terminals.
Health effects The
only practical way that ELF fields interact with living tissues is by
inducing electric fields and currents in them. However, the magnitude of
these induced currents from exposure to ELF fields at levels normally
found in our environment, is less than the currents occurring naturally
in the body.
Electric Field Studies:
Available evidence suggests that, apart from stimulation arising from
electric charge induced on the surface of the body, the effects of
exposures of up to 20 kV/m are few and innocuous. Electric fields have
not been shown to have any effect on reproduction or development in
animals at strengths over 100 kV/m.
Magnetic Field
Studies: There is
little confirmed experimental evidence that ELF magnetic fields can
affect human physiology and behaviour at field strengths found in the
home or environment. Exposure of volunteers for several hours to ELF
fields up to 5 mT had little effect on a number of clinical and
physiological tests, including blood changes, ECG, heart rate, blood
pressure, and body temperature.
Melatonin:
Some investigators have reported that ELF field exposure may suppress
secretion of melatonin, a hormone connected with our day-night rhythms.
It has been suggested that melatonin might be protective against breast
cancer so that such suppression might contribute to an increased
incidence of breast cancer already initiated by other agents. While
there is some evidence for melatonin effects in laboratory animals,
volunteer studies have not confirmed such changes in humans.
Cancer:
There is no convincing evidence that exposure to ELF fields causes
direct damage to biological molecules, including DNA. It is thus
unlikely that they could initiate the process of carcinogenesis. However,
studies are still underway to determine if ELF exposure can influence
cancer promotion or co-promotion.
Recent animal studies have not found evidence that ELF field exposure
affects cancer incidence.
Epidemiological
Studies: In 1979
Wertheimer and Leeper reported an association between childhood
leukaemia and certain features of the wiring connecting their homes to
the electrical distribution lines. Since then, a large number of studies
have been conducted to follow up this important result. Analysis
of these papers by the US National Academy of Sciences in 1996 suggested
that residence near power lines was associated with an elevated risk of
childhood leukaemia (relative risk RR=1.5),
but not with other cancers. A similar association between cancer and
residential exposure of adults was not seen from these studies.
Many studies
published during the last decade on occupational exposure to ELF fields
have exhibited a number of inconsistencies. They
suggest there may be a small elevation in the risk of leukaemia among
electrical workers. However, confounding factors, such as possible
exposures to chemicals in the work environment,
have not been adequately taken into account in many of them. Assessment
of ELF field exposure has not correlated well with the cancer risk among
exposed subjects. Therefore, a cause-and-effect link between ELF field
exposure and cancer has not been confirmed.
NIEHS Panel: The US National Institute of Environmental Health
Sciences (NIEHS) has completed its 5-year RAPID Program.The RAPID
Program replicated and extended studies reporting effects with possible
health implications, and conducted further studies to determine if
indeed there was any health consequence from ELF field exposure. In June
1998, NIEHS convened an international Working Group to review the
research results. NIEHS's
international panel concluded, using criteria established by the
International Agency for Research on Cancer (IARC), that ELF fields
should be considered as a "possible human carcinogen".
"Possible human
carcinogen" is the weakest of three categories ("possibly
carcinogenic to humans", "probably carcinogenic to
humans" and "is carcinogenic to humans") used by IARC to
classify scientific evidence on potential carcinogens. IARC has two
further classifications of scientific evidence: "is not
classifiable" and "is probably not carcinogenic to
humans", but the NIEHS Working Group considered there was enough
evidence to eliminate these categories.
"Possible human carcinogen" is a classification used to denote
an agent for which there is limited evidence of carcinogenicity in
humans and less than sufficient evidence for carcinogenicity in
experimental animals. Thus the classification is based on the strength
of scientific evidence, not on the strength of carcinogenicity or risk
of cancer from the agent. Thus, "possible human carcinogen"
means limited credible evidence exists suggesting that exposure to ELF
fields may cause cancer. While it cannot be excluded that ELF field
exposure causes cancer from available evidence, further focused, high
quality research is now needed to resolve this issue.
The decision of the NIEHS Working Group was based mainly on the
appearance of consistency in epidemiological studies suggesting
residence near power lines resulted in an apparently higher risk of
leukaemia in children. Support for this association was found in studies
relating childhood leukaemia incidence to proximity to power lines and
to magnetic fields measured for 24 hours in homes. Furthermore, the
Working Group also found limited evidence for an increased occurrence of
chronic lymphocytic leukaemia in the occupational setting.
International EMF
Project
WHO's
International EMF Project has been established to work towards resolving
the health issues raised by EMF exposure. Scientific reviews have been
conducted and gaps in knowledge identified. This has resulted in a
research agenda for the next few years that will ensure better health
risk assessments can be made. A formal task group meeting to assess the
results is scheduled by IARC in 2001. WHO will then adopt IARC's
conclusions and complete an assessment of non-cancer health risks in
2002.
International
StandardsThe
International Commission on Non-Ionizing Radiation Protection (ICNIRP)
has published guidelines on exposure limits for all EMF. The guidelines
provide adequate protection against known health effects and those that
can occur when touching charged objects in an external electric field.
Limits of EMF exposure recommended in many countries are broadly similar
to those of ICNIRP, which is a non-governmental organization (NGO)
formally recognised by WHO and a full partner in the International EMF
Project. It will reassess its guidelines once the EMF Project has
completed new health risk assessments.
Protective
Measures
Large conducting
objects such as metal fences, barriers or similar metallic structures
permanently installed near high voltage electrical transmission lines
should be grounded. If such objects are not grounded, the power line can
charge them to a sufficiently high voltage that a person who comes into
close proximity or contact with the object can receive a startling and
uncomfortable shock. A person may also receive such a shock when
touching a car or bus parked under or very near high voltage power
lines.
General public:
Since current scientific information is only weakly suggestive and does
not establish that exposure to ELF fields at levels normally encountered
in our living environment might cause adverse health effects, there is
no need for any specific protective measures for members of the general
public. Where there are sources of high ELF field exposure, access by
the public will generally be restricted by fences or barriers, so that
no additional protective measures will be needed.
Workers: Protection from 50/60 Hz electric field exposure
can be relatively easily achieved using shielding materials. This is
only necessary for workers in very high field areas. More commonly,
where electric fields are very large, access of personnel is restricted.
There is no practical, economical way to shield against ELF magnetic
fields. Where magnetic fields are very strong the only practical
protective method available is to limit of personnel.
EMF Interference
Strong ELF fields
cause electromagnetic interference (EMI) in cardiac pacemakers or other
implanted electromedical devices. Individuals using these devices should
contact their doctor to determine their susceptibility to these effects.
WHO urges
manufacturers of these devices to make them much less susceptible
to EMI.
Office workers may see image movement on the screen of their
computer terminal. If ELF magnetic fields around the terminal are
greater than about 1 µT (10 mG) this can cause interference with the
electrons producing the image on the screen. A simple solution to this
problem is to relocate the computer to another part of the room where
the magnetic fields are below 1 µT. These magnetic fields are found
near cables that provide electric power to office or apartment
buildings, or around transformers associated with power supplies to
buildings. The fields from these sources are generally well below the
levels that cause any health concern.
Noise, Ozone and
Corona
Noise in the form
of a buzzing or humming sound may be heard around electrical
transformers or high voltage power lines producing corona (see below).
While the noise may be annoying, there are no EMF health consequences
associated with these sounds.
Electrical devices
such as photocopiers or any device using a high voltage to function may
produce ozone, a colourless gas having a pungent smell. Electrical
discharges in the air convert oxygen molecules into ozone. While people
may easily smell the ozone, the concentrations produced around
photocopiers and similar devices are well below health standards.
Corona or electrical
discharges into the air are produced around high voltage power lines. It
is sometimes visible on a humid night or during rainfall and can produce
noise and ozone. Both the noise levels and ozone concentrations around
power lines have no health consequence.
What should be
done while research continues?
One of the
objectives of the International EMF Project is to help national
authorities weigh the benefits of using EMF technology against the
detriment should any adverse health effects be demonstrated, and decide
what protective measures, if any, may be needed. It will take some years
for the required research to be completed, evaluated and published by
WHO. In the meantime, WHO
recommends:
Strict adherence
to existing national or international safety standards: Such standards,
based on current knowledge, are developed to protect everyone in the
population.
Simple protective measures: Fences or barriers around strong ELF sources
help preclude unauthorised access to areas where national or
international exposure limits may be exceeded.
Consultation with local authorities and the public in siting new power
lines: Obviously power lines must be sited to provide power to
consumers. Despite the fact that ELF field levels around transmission
and distribution lines are not considered a health risk, siting
decisions are often required to take into account aesthetics and public
sensibilities. Open communication and discussion between the electric
power utility and the public during the planning stages can help create
public understanding and greater acceptance of a new facility.
An effective system of health information and communication among
scientists, governments, industry and the public can help raise general
awareness of programmes to deal with exposure to ELF fields and reduce
any mistrust and fears.
References
for further reading
ICNIRP (1998)
International Commission on Non-Ionizing Radiation Protection Guidelines
for limiting exposure to time varying electric, magnetic and
electromagnetic fields (up to 300 GHz). Health Physics 74(4), 494-522.
NIEHS (1998) Assessment of health effects from exposure to power-line
frequency electric and magnetic fields. Portier CJ and Wolfe MS (eds)
NIEHS Working Group Report, National Institute of Environmental Health
Sciences of the National Institute of Health, Research Triangle Park, NC,
USA, pp 523. Available from NIEHS
Repacholi M and
Greenebaum B (1998) Interaction of static and extremely low frequency
electric and magnetic fields with living systems: health effects and
research needs. Bioelectromagnetics (In press). (Summary report of WHO
scientific review meeting on static and ELF held in Bologna, 1997).
WHO (1997) WHO's Agenda
for EMF Research. World Health Organization publication WHO/EHG/98.13, WHO
Geneva. Also available on EMF web site
Source: Fact
sheet N°205, November 1998, Electromagnetic
fields and public health: extremely low frequency (ELF), http://www.who.int/mediacentre/factsheets/fs205/en/index.html:
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