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Environmental and Workplace Health

Environmental Radiation

We are constantly exposed to small amounts of radiation from the environment as we carry out our normal daily activities. Environmental radiation comes from the sky, the earth, and the air we breathe and can be categorized as natural or artificial.

Natural radioactive sources include:

  • Cosmic radiation comes from the sun and outer space. While most cosmic radiation is absorbed by the atmosphere, a small amount reaches the earth's surface to which we are exposed. The exposure to this type of radiation is higher for people living above sea level.
  • Radon is produced through the decay of uranium and thorium that are found naturally in the earth's crust. One of the products of this decay is radon, which is an inert gas that is capable of moving from the ground into the air we breathe.
  • Primordial and terrestrial radiation are present in rocks and soils and occur when naturally radioactive isotopes of uranium, thorium and potassium decay within the earth's crust.

Artificial (or man-made) radioactive sources include:

  • Fallout radiation, which results from past atmospheric nuclear bomb tests. During the 1950s and 1960s many test explosions released radioactive products into the atmosphere and these materials have been transported around the world and eventually fall back to the earth.
  • Radiation is released to the environment during operation of nuclear reactors and supporting facilities such as mines, mills and fuel fabrication plants.
  • Radiation is generated from or for nuclear medicine, consumer products, military and industrial applications and nuclear waste management

Health Canada investigates the potential health effects to the Canadian population from natural and technological sources of environmental radioactivity. Our programs include: