Radiation Occupational exposures and protection A. H. Mehrparvar, MD Occupational Medicine department Yazd University of Medical Sciences

Non-ionizing radiation

 Sources Ultraviolet light Visible light Infrared radiation Microwaves Radio & TV Power transmission

 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 Can damage the eye (cornea)  Germicidal lamps  Eye damage from sun light  Skin cancer

UV effects  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)

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 ” )

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

Laser  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.laser  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. 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.

 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.

Microwave & Radiofrequency Radiation  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).

 Sources of radiofrequency and of microwaves are primarily:  Radio and television broadcast antenna  Communications equipment such as cellular & PCS, satellite, etc.  Cooking (microwave ovens)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  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).thermal