Radiation
Every day, people are exposed to radiation from natural and man-made sources. Some forms of radiation exposure can cause cancer.
What is radiation?
Radiation is energy that travels through space from many different sources, such as the sun, electrical appliances and x-rays. There are two main kinds of radiation in the electromagnetic spectrum:
- ionizing radiation – for example, cosmic, gamma and x-rays
- non-ionizing radiation – for example, ultraviolet, visible light, infrared, microwaves and radio waves
Ionizing radiation
Ionizing radiation has enough energy to break chemical bonds between molecules, or to form charged molecules (cause ionization). This means that it is strong enough to damage cells and DNA. Exposure to ionizing radiation has been shown to increase the chance of developing cancer. The risk of developing cancer increases as the amount and length of exposure increases. Some types of cancer may develop 10 or more years after the exposure. Other types, such as leukemia, may develop within 2 years after short-term exposure to a high dose of radiation. 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
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.
Radon
Radon gas, released from the natural breakdown of uranium, is an example of natural background radiation. Exposure to high radon levels can increase the risk of lung cancer. The World Health Organization’s International Agency for Research on Cancer (IARC) classifies radon as a known cancer-causing substance.
Medical radiation
Diagnostic tests such as x-rays, CT scans and radiation therapy for cancer are types of medical radiation exposure.
Non-medical radiation
Testing and using nuclear weapons as well as nuclear power generation are sources of non-medical radiation exposure.
Non-ionizing radiation
Non-ionizing radiation does not have enough energy to break bonds between molecules, and is not as strong as ionizing radiation. However, exposure to some types of non-ionizing radiation can still cause harm.
Sources of non-ionizing radiation exposure include:
The sun produces radiation, including visible and ultraviolet rays. Exposure to the sun is a known risk factor for the most common types of skin cancers. Ultraviolet radiation can also be produced artificially – for example, by the bulbs used in indoor tanning beds.
Extremely low frequency (ELF) waves associated with electricity production and distribution produce magnetic fields. Overall, research has not found a link between ELF magnetic fields and cancer, but there are still unanswered questions about a possible link with childhood leukemia.
Radiofrequency waves are used by radio and TV broadcasts, satellites, cell phones and cell phone towers, and wireless Internet to transmit and received information. Microwave ovens and radars work using microwaves.
Suggested links
Canada
Health Canada – Radiation
Last modified on:
04 February 2010
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