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Tritium is a radioactive form of hydrogen that is created naturally in the environment, and is also released in very small amounts by Canadian nuclear facilities as tritiated water.

Since radioactivity poses a health risk, the Ontario government has placed limits on the allowable amount of tritium in drinking water.

Tritium levels in drinking water obtained from Lake Ontario are very low and have never exceeded the Provincial limit.

How does radiation affect my health?

Exposure to any radiation source can result in an increased risk of cancer, genetic defects and reproductive effects. Since we are exposed to radiation from many natural (e.g., radon gas in soil) and human sources (e.g., medical x-rays), it is important to control our total radiation exposure, not just our exposure to one source.

We can be exposed to tritium by eating and drinking contaminated food and water, and breathing contaminated air.

Where does tritium come from?

Tritium is produced naturally when cosmic radiation and gases in the atmosphere interact.

Tritium also originates from human activities such as nuclear weapons testing which has slightly contaminated all surface water supplies around the world.

Canadian designed nuclear reactors (e.g., CANDU) also produce tritium. An accidental release of "heavy water" used to cool the reactors can result in the release of tritium into the environment. Small amounts of tritium are also released into Lake Ontario during the normal operations of the nuclear generating facilities.

How much tritium is in my drinking water?

In Canada, the average tritium concentration in drinking water ranges from 5 to 10 becquerels per litre. The Becquerel is an international measure of radioactivity.

Water samples taken near Pickering and Darlington Nuclear Generating Facilities occasionally have a tritium concentration of approximately 20 becquerels per litre which is well below the interim Provincial limit for tritium of 7,000 becquerels per litre in drinking water.

What is being done to make sure tritium levels stay low?

Ontario Power Generation in association with Provincial and Regional authorities has developed a comprehensive emergency response plan in the event of an accidental tritium release to protect the health of the residents of Durham Region.

Daily samples of drinking water are obtained from all water treatment plants within 20 kilometres of the two nuclear generating stations on Lake Ontario. The Radiation Protection Branch of the Ontario Ministry of Labour tests these samples for tritium content. Ontario Power Generation (formerly Ontario Hydro) also tests water samples as part of its own monitoring program and the Health Department closely monitors the results.

More information can be obtained from

Durham Region Health Department, Environmental Help Line 905-723-3818 or 1-888-777-9613

April 22, 2013