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Radiation is energy that travels through space in the form of waves or particles. There are two types of radiation: ionizing and non-ionizing.

Ionizing radiation

Ionizing radiation has enough energy to break chemical bonds between molecules or to form charged molecules (cause ionization). This means that ionizing radiation is strong enough to damage cells and DNA and strong enough to increase the chance of developing cancer.

Sources of ionizing radiation exposure include:

  • natural background radiation (sources of exposure include cosmic rays from the solar system and radioactive materials in the soil and rocks)
  • background radiation from human activities (includes testing and using nuclear weapons as well as generating nuclear power)
  • radon
  • medical radiation
Non-ionizing radiation

Non-ionizing radiation isn’t as strong as ionizing radiation, and it doesn’t have enough energy to break bonds between molecules. But being exposed to some types of non-ionizing radiation can still harm you.

Sources of non-ionizing radiation exposure include:

  • radiofrequency fields (including cell phones, cell phone towers and microwave ovens)
  • electromagnetic fields (including power lines and household appliances)
  • ultraviolet (UV) rays (including the sun and indoor tanning beds)
  • How you’re exposed to radiation

    Every day, people are exposed to radiation from natural sources (such as radon and solar and ultraviolet radiation) and man-made sources (such as cell phones, electromagnetic fields and medical radiation).

  • Radiation and cancer

    Some forms of radiation, such as ionizing radiation and ultraviolet rays, are known to cause cancer. Cancer risk is related to the type and dose of radiation a person is exposed to, and it may take 10 years or more after exposure before cancers appear. The greatest risks come from larger doses, longer exposures and high-strength forms of radiation. The risk of developing cancer increases as the amount and length of exposure increases.

    The evidence about ionizing radiation comes from many sources:

    • animal and laboratory experiments
    • studies of Japanese survivors of the atomic bombings
    • observations of certain occupational groups and populations
    • outcomes of patients who were treated with medical radiation at high doses

    Not all forms of radiation have the same potential to cause health problems and long-lasting damage. Learn more about risks associated with specific types of radiation and how to reduce your exposure by visiting our pages about cell phones, electromagnetic fields, radon and solar and ultraviolet radiation.

  • Suggested links for more information
    General information about radiation

    Learn more about sources of radiation and the government’s role in protecting Canadians from potentially harmful effects of exposure.

    Health Canada – Radiation

    CAREX Canada – Carcinogen profile: ionizing radiation

    World Health Organization – Ionizing radiation

    US Environmental Protection Agency – Radiation: non-ionizing and ionizing



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