FAQ - Health Effects, Dosimetry and Radiological Protection of Tritium

Q1. What is tritium?
Q2. What is the Tritium Studies Project?
Q3. What are the objectives of the Health Effects, Dosimetry and Radiological Protection of Tritium report?
Q4. What does the report cover?
Q5. What does the report conclude?
Q6. Is there a health risk related to tritium exposure in Canada?
Q7. Was this report peer-reviewed?
Q8. How will the report affect the regulation of CNSC licensees?

---

Q1. What is tritium?

A1. Tritium is a radioactive form of hydrogen that occurs both naturally and as a by-product in nuclear reactors and tritium processing facilities. Tritium exposure can pose a health risk if it is ingested through drinking water or food, inhaled or absorbed through the skin.  Releases of tritium by nuclear reactors and tritium processing facilities are regulated by the CNSC to ensure the health and safety of workers and the public, and the protection of the environment.

Q2. What is the Tritium Studies Project?

A2. In January 2007, the Commission Tribunal directed CNSC staff to initiate research studies on tritium releases in Canada, and to study and evaluate tritium processing facilities exercising the best practices around the globe.  In response, the CNSC has undertaken several research projects under the banner of the Tritium Studies Project. This research will enhance the information used in the regulatory oversight of tritium processing and tritium releases in Canada.

Q3. What are the objectives of the Health Effects, Dosimetry and Radiological Protection of Tritium report?

A3. The report’s objectives were to provide:

• an independent review of scientific literature to assess the health risk to workers and the public from exposures to tritium
• an assessment of Canadian and international dosimetry practices for tritium intakes
• a review of the current approaches for limiting exposure to tritium

Q4. What does the report cover?

A4. The following information is reviewed and summarized in the report:

• an overview of tritium’s physical, chemical and radiological properties
• a detailed analysis of the adverse health effects of tritium radiation, including reviews of laboratory and epidemiological studies
• a review of experimental studies estimating the relative biological effectiveness (RBE) of tritium radiation
• a description of biokinetic models and dosimetry of tritium
• a review of the approach taken by the International Commission on Radiological Protection (ICRP) for protection from tritium and possible modification of the radiation weighting factor (wR)

Q5. What does the report conclude?

A5. The report draws the following conclusions:

• Tritium beta radiation is about 1.4 times more effective in causing biological effects than x-rays and 2.2 times more effective than gamma rays. This means that the health risk of tritium is respectively 1.4 and 2.2 times higher than for these other types of radiation.
• The use of a radiation weighting factor of 1 in the current ICRP radiation protection framework has not decreased the level of protection afforded to workers or members of the public.  This is because implementation of optimization has resulted in exposures to tritium that are very low and well below doses at which an increased risk of cancer has been observed.
• Current dosimetry and biokinetic models for assessing dose are acceptable for radiation protection purposes.
• Studies have shown that tritium exposures at current levels in Canada are highly unlikely to cause adverse health effects.
• Canada’s current regulatory framework has effectively controlled tritium exposures.

Q6. Is there a health risk related to tritium exposure in Canada?

A6. In Canada, total radiation exposures to workers and the public are low and tritium represents only a small fraction of these exposures.

There is little evidence to suggest that radiation-induced health effects (such as increased birth defects, cancer incidence or mortality) occur in populations exposed to tritium at current environmental or occupational levels. This is based on extensive research of other types of radiations received at much higher levels. This suggests that any tritium-specific risk is small and not distinguishable from the risk of similar health outcomes in the general population.

Q7. Was this report peer-reviewed?

A7. Yes. To validate this study, the CNSC had it peer-reviewed by the following prominent and respected experts in the fields of radiation biology, dosimetry and epidemiology.  Their expertise in the area of tritium research makes them suitable to conduct the review.

Dr. John Boice, Professor of Medicine Vanderbilt University School of Medicine and Scientific Director International Epidemiology Institute Maryland, USA	Dr. Barrie Lambert, Radiation Biologist St Bartholomew’s Hospital Medical College London, U.K. (retired)
Dr. David Kocher, Senior Scientist SENES Oak Ridge Tennessee, USA	Dr. John Harrison, Radiation Biologist Health Protection Agency U.K.
Dr. Richard Richardson, Internal Dosimetrist Atomic Energy of Canada Ltd Ontario, Canada	Dr. Richard Wakeford, Visiting Professor in Epidemiology Dalton Nuclear Institute, University of Manchester, U.K.

Q8. How will the report affect the regulation of CNSC licensees?

A8. The Health Effects, Dosimetry and Radiological Protection of Tritium report does not make recommendations. The information will be analyzed by CNSC staff in combination with the results of the other Tritium Studies Project reports. A synthesis report, including any recommendations that may impact oversight and regulation, will be submitted to the Commission Tribunal in June 2010.