Download Human exposure to Electromagnetic Fields

Human exposure to
Electromagnetic Fields
Electromagnetic Frequency Spectrum
Electrosmog or radiation Pollution
Interaction of Humans with
Electromagnetic Fields
ELF Electric and Magnetic Fields and
RFR (refer to handout given).
Bioeffects of ELF Fields and
Bioeffects of RFR.
The Electromagnetic Frequency Spectrum
Depending on the frequency, electromagnetic
radiation is classified as either non-ionizing or ionizing
non-ionizing radiation
ionizing radiation
• is electromagnetic
radiation that does not
have sufficient energy to
cause ionization in living
system
• Natural sources:- the sun,
distant radio stars, other
cosmic sources,
terrestrial sources like
lightning
• ionizing radiation is
radiation that has
sufficient energy to
remove electrons from
atom.
• One source:- the nuclei
of unstable atoms
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The Electromagnetic
Spectrum
Ionizing
You should know the
different types of
electromagnetic radiation
and their typical uses.
Non-ionizing
The Electromagnetic
Spectrum (cont’d)
The complete range of
electromagnetic radiation, from
radio waves to gamma rays,
including the visible spectrum.
All types of electromagnetic
radiation are basically the same
phenomenon, differing only by
wavelength, and all move at the
speed of light.
The amount of energy a photon
has makes it sometimes behave
more like a wave and sometimes
more like a particle. This is
called the "wave-particle duality"
of light.
Low energy photons (such as
radio) behave more like waves,
while higher energy photons
(such as X-rays) behave more
like particles.
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The Electromagnetic Spectrum (Cont’d)
-Examples of Ionizing RadiationGamma Radiation
• Gammer rays are useful for checking individual organs when user as a
tracer.
A radioactive isotope that emits gamma rays is injected into the body
and when it has circulated it can be detected by a camera to give
either a still or moving picture.
• Gamma radiation is used to:
Radiotherapy
Sterilise surgical instruments.
Kill harmful bacteria in food.
Kill cancer cells or other abnormal cells.
X-Rays
• X-rays are the most penetrative of the electromagnetic waves, a
property that is useful for medical imaging, diagnostic.
When an X-ray is taken:
X-rays are passed through the body and detected by a photographic plate.
the X-rays pass through the flesh and are absorbed by the bone.
bone shows up white on the photograph and the flesh appears dark.
a bone fracture is seen as a dark line on the white bone
The Electromagnetic Spectrum (Cont’d)
-Examples of Ionizing RadiationUltraviolet radiation
Ultraviolet radiation is higher energy and shorter wavelength than
light.
Much of the ultraviolet radiation from the sun is absorbed by the
atmosphere but in the summer months less is absorbed than in
winter.
Ultraviolet radiation is used in:
Sun beds
Security pens
Fluorescent lights (coatings inside the light absorb the ultraviolet light
and re-emit it as visible light)
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The Electromagnetic Spectrum (Cont’d)
-Examples of Non-Ionizing RadiationInfra red radiation
Infra red radiation has a longer wavelength and a lower energy than
light, so it is less harmful than ultraviolet radiation.
Infra red radiation is used:
in cooking; toasters and grills transfer energy to food by infra
redradiation.
in night time photography.
in remote controls for devices such as televisions and hi-fi's
Microwaves
Cooking
The microwaves used in cooking have a wave length around 12 cm, so
they fit into the radio wave part of the spectrum.
Radio waves of this wavelength can penetrate a few centimeters into
food, and they have the right frequency to be absorbed by water
molecules as they pass through.
Communications
Microwave radiation can also be used to transmit signals such as mobile
phone calls. When a mobile phone is within range the Microwave
transmitters and receivers on buildings and masts communicate with it.
The Electromagnetic Spectrum (Cont’d)
-Examples of Non-Ionizing RadiationRadio
Television and radio
Radio waves have lower frequencies and longer wavelengths than
microwaves. National television and radio programs are broadcast using
radio waves.
Radio waves are defracted around hills and buildings so there is less
chance of a “shadow” causing poor reception. Radio waves have a low
frequency which limits the amount of information that can be
transmitted.
Longer wavelength radio waves are reflected from an electrically
charged layer of the upper atmosphere. This means that they can reach
receivers that are not in the line of sight because of the curvature of
the Earth's surface.
Image courtesy of www.bbc.co.uk
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Electrosmog ?
http://www.electrosmog.org.uk/
•
•
3G telephone masts, indoor
cordless (DECT) telephones
and Wi-Fi networks are just a
few examples of new
electromagnetic sources.
Then there are electric
blankets, microwave ovens,
computers, and bluetooth
devices.
•
University campuses and many
public spaces are now
wirelessly networked.
•
Soon there will be many more
wireless devices.
•
Personal Area Networks or
Body Area Networks are
evolving enabled by new short
range wireless standards WSN
(IEEE 802.15.4) and Zigbee.
Electrosmog or radiation pollution
Electrosmog is a relatively new term for
radiation pollution recently used to describe
all artificially generated electromagnetic
fields.
Electrosmog occurs everywhere voltages
and currents are present; in the home,
industry and commerce.
Mostly, human senses do not register these
fields, but they are nevertheless affected by
them
Tool or instrument that is used to measure
magnetic field exposure (home, office, lab,
school etc,) is EMF meter
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Interaction of Humans with
Electromagnetic Fields
The senses of the human body and regulatory systems
operate using minute electric currents and voltages.
These quantities can be measured, for example the ‘brain
waves’ can be recorded on an electroencephalograph
(EEG) and electrocardiogram (ECG) is a test that records
the electrical activity of the heart.
Artificially created electromagnetic fields induce much
higher currents and voltages in the human body than are
naturally present.
Although the human body can compensate for a great
many things, it is not yet fully known what effect
electromagnetic fields have on human health, and much
more research is to be done
Bioeffects of ELF Fields and
Bioeffects of RFR.
Bioeffects of Extremely Low Frequency (ELF) Fields
Acceptable exposure limits of ELF fields are mostly
expressed in terms of magnetic fields.
Coupling of human beings to electric fields is not same, i.e.
it is observed that electric fields induced inside the human
bodies are generally less than about 10-7 of the field outside
the body and rarely exceed about 10-4 of the external field.
Bioeffects of Radio Frequency (RF) Radiation.
The interaction of RF fields with living systems and their
related bioeffects can be considered at various levels
including the molecular, subcellular, organ, or system level
or the entire body.
Can be classified as follows:
High level (thermal) effects
Intermediate level (athermal) effects
Low level (non-thermal) effects
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