Transcript Occupational Eye Injuries

Radiation
Occupational exposures and
protection
A. H. Mehrparvar, MD
Occupational Medicine department
Yazd University of Medical Sciences
Non-ionizing radiation
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Sources
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Ultraviolet light
Visible light
Infrared radiation
Microwaves
Radio & TV
Power transmission
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Ultraviolet – Black light – induce
fluorescence in some materials
Vision – very small portion that animals use
to process visual information
Heat – infrared – a little beyond the red
spectrum
Radio waves – beyond infrared
Micro waves
Electrical power transmission – 60 cycles
per second with a wave length of 1 to 2
million meters.
UV
Sun light
 Most harmful UV is absorbed by the
atmosphere – depends on altitude
 Fluorescent lamps
 Electric arc welding
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Can damage the eye (cornea)
Germicidal lamps
 Eye damage from sun light
 Skin cancer
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UV effects
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High ultraviolet – kills bacterial and other
infectious agents
High dose causes - sun burn – increased risk
of skin cancer
Pigmentation that results in suntan
Suntan lotions contain chemicals that
absorb UV radiation
Reaction in the skin to produce Vitamin D
that prevents rickets
Strongly absorbed by air – thus the danger
of hole in the atmosphere
Visible light
Energy between 400 and 750 nm
 High energy – bright light produces of
number of adaptive responses
 Standards are set for the intensity of
light in the work place (measured in
candles or lumens)
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IR
Energy between 750 nm to 0.3 cm
 The energy of heat – Heat is the
transfer of energy
 Can damage – cornea, iris, retina and
lens of the eye (glass workers – “glass
blower’s cataract”)
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Microwave and radio wave
Energy between 0.1 cm to 1 kilometer
 Varity of industrial and home uses for
heating and information transfer
(radio, TV, mobile phones)
 Produced by molecular vibration in
solid bodies or crystals
 Health effects – heating, cataracts
 Long-term effects being studied
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Laser
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That depends upon the output power of the laser. Very low power lasers
are safe. Moderate to high power lasers can be hazardous to the eyes and,
in some cases, the skin. Countries such as the U.S.A., where many diode
laser pointers come from, have laser safety standards with mandatory
classification and labeling requirements. In this system, all lasers are
classified into one of four classes. The classification number (one to four)
and appropriate warning statements must be labeled on the device. A
class 1 laser does not present a hazard.
A class 2 laser is visible, not inherently safe, but the eye is protected by
one’s "blink aversion response" to the bright light.
Class 3 lasers fall into one of two sub-classes, i.e., 3a and 3b.
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Class 3a: For most individuals, eye protection is afforded by the "blink aversion
response" to class 3a lasers, except when the laser is viewed using optical aids
(telescopes, binoculars).
Class 3b lasers are dangerous, and can damage eyes instantaneously upon
exposure. They require a longer exposure time to burn skin.
Class 4 lasers are dangerous, and can damage eyes and skin
instantaneously upon exposure. Some can damage eyes even from a
diffuse reflection. Class 4 lasers can cause materials to ignite.
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Conclusions
Laser pointers, including diode laser pointers, are useful tools that
should not be used by children or irresponsible individuals.
In some countries the sale of class 3a laser pointers is banned. It
is recommended that the use of laser pointers be restricted to
devices in classes 1 or 2 in preference over the class 3a, diode
laser pointers.
Retailers should be discouraged from selling class 3a laser
pointers the general public.
The control of the importation and sale of radiation emitting
devices, such as lasers, is the responsibility of the federal
government. No regulations controlling the importation and sale of
laser pointers have been established in Canada to date.
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Microwave & Radiofrequency Radiation
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Microwave and radiofrequency radiation is
electromagnetic radiation that is lower in
frequency and therefore longer in wavelength
than infrared radiation. "Radiofrequency" is the
name given to that section of the electromagnetic
spectrum from frequencies of 300 kHz to 300
GHz. In general the section of the
electromagnetic spectrum from frequencies of
approximately 300 MHz to 300 GHz and
wavelengths of approximately 1 meter (m) to 1
millimeter (mm) are called microwaves. Although
some consider microwaves not to include lower
frequencies and to start at 800 MHz with a
wavelength of 37.5 centimeters (cm .)
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Sources of radiofrequency and of microwaves are
primarily:
Radio and television broadcast antenna
Communications equipment such as cellular &
PCS, satellite, etc.
Cooking (microwave ovens)
Civilian, police and military radar
A variety of industrial inductive and dielectric
heating devices
Medical devices such as magnetic resonance
imaging (MRI), and diathermy devices
Health concerns
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The primary health concern of microwave
radiation is adverse effects associated with whole
or partial body thermal exposure. A clear
example of a thermal exposure situation is the
heating of animal tissue (e.g. hamburger) in a
microwave oven. The microwave electromagnetic
radiation "cooks" the animal tissue. Avoiding
damaging thermal exposure levels is
accomplished by keeping one's exposure below
recommended maximum specific absorption
rates (SAR's). However since SAR is difficult to
determine, safety standards have also adopted
maximum allowable power density exposure
limits measured in units of watts per square
meter (W/m2).