Canadian Centre for Occupational Health and Safety
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Health and Safety: Teaching Tools



Radiation is energy spreading out from a source. When we switch on a light bulb, light comes to us by the radiation process. When the sun rises, we feel warm because the sun radiates energy in the form of light and heat. Radiation does not need a medium to travel. If you place an alarm clock in a jar and evacuate the jar using a vacuum pump, you will not hear the alarm. Sound needs a medium to travel from one point to another. But we will see the radium dial in the dark because light does not
need a medium to travel.

Radiation - Two Categories

Radiation is divided into two categories:

  1. Ionizing radiation
  2. Non-ionizing radiation

Ionizing Radiation

Ionizing radiation is given off by x-ray machines and radioactive materials. Some amount of background ionizing radiation is present everywhere. It comes from the earth and outer space.

Ionizing radiation can:

Ionizing Radiation

Kill a cell - no effect is noticeable if only a few cells are killed. In case of extremely high exposure, such as nuclear accidents, too many cells may be killed resulting in sickness or death.

Alter a cell - damaged cells may multiply and cause cancer many years later.

Alter a reproductive cell - an altered reproductive cell may cause genetic defects in children and grandchildren - hereditary effects.

Affect the developing fetus - and may cause abnormalities in a newborn baby if a pregnant woman is exposed, radiation.

Exposure is minimized by:

Ionizing Radiation

  • limiting the exposure time and avoiding all unnecessary exposure,
  • using a shielding such as lead sheets to stop radiation before it reaches a person,
  • staying as far away as possible from a source, and
  • avoiding contamination of the hands and body by radioactive material.

Non-ionizing Radiation

Non-Ionizing Radiation

Radiation from sun, light bulbs, electric power lines, radio and TV antenna, lasers etc., is considered to be non-ionizing radiation.

Research indicates that long term exposure to UV rays may increase the risk of skin cancer. Minimizing exposure is the key to protection. This is done by:

Non-Ionizing Radiation

  • staying as far away from the source as much as possible,
  • minimizing exposure time, and
  • stopping radiation before it reaches people (e.g. sunglasses and barrier creams for protection against UV rays).

Electromagnetic Radiation

Computer monitors produce two types of electromagnetic radiation:

Electormagnetic Radiation

  • VLF ( Very Low Frequency) radiation from electronic circuits that produce pictures and letters on the screens. The source of VLF is the electronic circuit inside the computer monitor that produces pictures and letters on the screen.
  • ELF (Extremely Low Frequency ) radiation from the use of electrical power. The source of ELF is the electrical power supply to the computer monitor. Its frequency is 60 cycles per second or 60 Hz in some countries.

The levels of ELF and VLF electromagnetic fields measured around terminals are well below recommended exposure guidelines. Some researchers have reported adverse effects from exposure to electromagnetic fields. It has not been scientifically proven that exposure to these emissions causes negative health effects. In this situation of uncertainty, prudent avoidance is recommended. This means that we must avoid all unnecessary exposures. Distance is the best protection. At about arm's length distance, the exposure level is negligible.

Many computer users experience eye irritation. Generally these problems are related to glare from the screen. Workstation design and the work practice are causes for a number of hand and wrist pain as well as muscle and joint pain. (See Ergonomics Notes for details.)

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