Radiation is energy that is emitted from a source in the form of waves or particles (Canadian Nuclear Safety Commission). It is found throughout our environment and is emitted from both natural and artificial sources. Natural sources account for most of the radiation dose that people receive each year (World Health Organization). Natural sources of radiation include terrestrial radiation (emitted from soil and rock), cosmic radiation (emitted from the sun) and internal radiation (breathing in radon gas). Artificial sources of radiation include X-ray machines, microwave ovens and cell phones.
Radiation is generally divided into two types, ionizing and non-ionizing radiation.
Ionizing radiation is a high energy radiation that can add or remove electrons from atoms to form ions, as it passes through a substrate such as living tissue. Chronic and acute exposure to this type of radiation can damage genetic material and result in cancer and/or death. Ionizing radiation includes alpha particles, neutrons, gamma rays and X-rays. Products that emit ionizing radiation include X-ray machines and diagnostic tracers used in nuclear medicine.
Non-ionizing radiation is a lower energy type radiation and is unable to ionize matter and is unlikely to cause cancer. However, this type of radiation can damage human tissue through heating and may lead to heat stress. Non-ionizing radiation includes the spectrum of ultraviolet, visible, and infrared light, micro and radio waves. Products that emit non-ionizing radiation include microwave ovens, cordless phones and television stations (Canadian Nuclear Safety Commission).
Worker exposure to ionizing radiation is measured by radiation dose and its limits, also known as Threshold Limit Values (TLVs), are provided by the American Conference of Governmental Industrial Hygienists (ACGIH). The biological effect of radiation on the human body is dependent on the absorbed dose, the type of radiation and which tissue or organ is being exposed to the radiation.
Ionizing radiation dose can be quantified in three different ways:
- Absorbed dose is the energy deposited in a kilogram of a substance (human tissue) by radiation. The absorbed dose is measured by a unit called the gray (Gy).
- Equivalent dose is the absorbed dose weighted for the degree of effect of different types of radiations (alpha vs beta particles, etc.). The equivalent dose is measured in Sieverts (Sv), where 1 Sv of alpha radiation will have the same biological effect as 1 Sv of beta radiation. Equivalent dose is calculated by multiplying the absorbed dose by the radiation weighting factor.
- Effective dose is used to measure how exposure to radiation can affect the human body overall. This measurement weighs the equivalent dose and the impact radiation has on a specific tissue or organ. The impact radiation has on a specific tissue is factored into the effective dose because each tissue/organ has a varying sensitivity to radiation. For instance, bone marrow is more sensitive to radiation compared to muscle tissue. The unit used for effective dose, is also Sieverts, but it is the equivalent dose multiplied by the tissue weighting factor WT
Radiation is discussed in Part 18 of the Manitoba Workplace Health and Safety Act. This Part applies to every workplace where ionizing or non-ionizing radiation is used. However, this Part does not apply to (a) radiation sources subject to the Nuclear Safety and Control Act (Canada); and (b) radiation provided to a medical or dental patient.
Employers must (a) develop and implement safe work procedures respecting the use of radiation in the workplace to ensure that workers are not exposed to radiation in excess of limits established in the ACGIH publication Threshold Limit Value for Chemical Substances and Physical Agents and Biological Indices; (b) train workers in the safe work procedures; and (c) ensure that workers comply with the safe work procedures.
When workers in a workplace are, or may be, exposed to levels of radiation in excess of the threshold limit values for radiation, set out by ACGIH, the employer must implement procedures that control exposure to radiation in the workplace. When implementing control measures, it is important to consider engineering controls, administrative controls, and lastly personal protective equipment. In addition to control measures, employers must inform a worker who may be exposed to radiation in the workplace of the potential hazards of radiation exposure.
Check out our Shop Talk and safe work procedure template on radiation. (Below the FAQs are more resources related to radiation.)