Standards and Guidelines for Tritium in Drinking Water (INFO-0766)

DISCLAIMER 

The information contained in this document is not exhaustive, however it can be considered to be reasonably complete in regards to the major emitters of tritium in the world. The information is current as of September 2007.

This factual document does not attempt to analyze the information or draw conclusions.

TABLE OF CONTENTS

• Tables
• Acronyms
• Glossary
• Executive Summary
• 1. Introduction
• 2. Radiation Protection Basis of Drinking Water Guidelines
• 3. Regulatory Approaches
• 4. Differences Between Canadian and International Approaches
• 5. Current Tritium Levels in Drinking Water
• References
• Appendix

Top

TABLES

Table 1. Radiation Units

Table 2. International Limits for Tritium in Drinking Water

Table 3. Drinking Water Tritium Concentration near Nuclear Sites

Table 4. Drinking Water Tritium Concentration in Background Locations

Table A1. Summary Table of International Limits for Tritium in Drinking Water

ACRONYMS 

GLOSSARY 

Table 1.Radiation Units

EXECUTIVE SUMMARY 

• Natural background levels of tritium can be found everywhere in the environment.
• In Canada, the control of tritium releases to the environment is important, since this element is a by-product of CANDU nuclear reactors and is used to produce gaseous tritium light sources.
• The guidelines for radionuclides in drinking water adopted by the majority of the international community are based on international radiation protection methodologies and recommendations of the International Commission on Radiological Protection (ICRP) and the World Health Organization (WHO).
• The European Union, the United States, Australia and Finland use variations of the WHO approach to arrive at differing guideline reference levels.
• In Canada, current tritium levels in drinking water are several orders of magnitude lower than the guideline reference level (GL) of 7,000 Bq/L near nuclear facilities, and similarly well below the European Union’s GL of 100 Bq/L.

1. INTRODUCTION

1.1 Tritium in the Environment

Tritium is a radioactive form of hydrogen with a physical decay half-life of 12.3 years.It emits very low-energy beta radiation, which is completely absorbed by common materials such as sheets of plastic, glass or metal, and cannot penetrate the top dead layer of skin in humans.Exposure can nevertheless pose a risk if the element is ingested in drinking water or food, or inhaled or absorbed through the skin.In Canada, the control of tritium releases to the environment is particularly important, since CANDU reactors produce significantly more tritium than most other types of reactors due to the use of heavy water (deuterium) in the moderator and heat transport system.Tritium is also used by a few industries to produce gaseous tritium light sources.Much smaller quantities are used in research applications, and as a tracer in oil and gas exploration.Tritium also forms naturally in the upper atmosphere due to the continuous bombardment of atmospheric gases by high energy cosmic rays.When it is present either naturally or artificially, tritium may be incorporated into water, thus entering the natural hydrological cycle.Hence, natural background levels of tritium can be found everywhere in the environment, including water, soil, and vegetation.Additional information on the presence and use of tritium in Canada can be found in a recent document produced by the Canadian Nuclear Safety Commission [CNSC, 2007a].

1.2 Regulation of Tritium Releases in Canada

Under the Nuclear Safety and Control Act (NSCA), the mandate of the Canadian Nuclear Safety Commission (CNSC) includes the dissemination of scientific, technical and regulatory information concerning the activities of the CNSC, and the effects on the environment and the health and safety of persons, of the development, production, possession, transport and use of nuclear substances.Under the NSC Act, the CNSC regulates facilities that possess more than 1 GBq (1 x 109 Bq) of tritium.The CNSC regulates potential releases of tritium to the environment through several licensing requirements, including absolute limits on how much tritium can be released on a license-specific basis.This is typically accomplished by imposing quantitative Derived Release Limits (DRL) on tritium entering air or water.These quantities are based on limiting releases to levels less or equal to the prescribed public dose limit of 1 mSv.Current tritium DRLs and amounts actually released relative to these absolute limits are summarized in [CNSC, 2007b].

General requirements for major nuclear facilities licensed by the CNSC include environmental protection policies, programs, and procedures that make adequate provision for protection of the environment.These are typically referred to collectively as an environmental management system, and include two key provisions for the control of releases of radioactivity to the environment: ALARA and Action Levels.ALARA is the paramount requirement for all licensed activities under the Radiation Protection Regulations; according to it, releases must be kept “As Low As Reasonably Achievable”, social and economic factors being taken into account.Action Levels are also required, and are set such that an exceedence may indicate a loss of control.Action levels are typically set for gaseous or liquid effluent concentrations or for activity levels in the environment.Response to an action level includes a thorough investigation of the cause, remedial actions and reporting to the CNSC.In addition, licensees usually establish administrative controls set well below action levels to trigger investigations into potentially unusual operating conditions and their root causes.

The CNSC requires regular reporting of the results of monitoring of routinely-discharged radioactive effluents (including the total activity or total amount released), and, at a minimum, annual reports of environmental monitoring results.Lastly, the CNSC also requires the reporting of any release of a nuclear substance into the environment at a quantity not authorized by the NSC Act, regulations or the license, or any unmeasured release.

1.3  Scope of this Document

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 in the world exercising best practices.In response, CNSC staff initiated a “Tritium Studies” project with several planned information gathering and research activities extending to 2010 (a fact sheet is available at www.nuclearsafety.gc.ca).The objective of this project is to enhance the information available to guide regulatory oversight of tritium processing and tritium releases in Canada.

This present report of drinking water standards and guidelines is a factual report, one of a series of public information documents being produced through the auspices of the Tritium Studies project.Its purpose is threefold:

• to summarize criteria on a national and international basis from readily-available public sources of information, along with the scientific and policy basis underlying these criteria;

• to discuss the Canadian federal drinking water guideline of 7,000 Bq/L relative to criteria or guidance from other jurisdictions; and

• to provide a perspective on the need for any revisions to the existing regulatory approach for tritium by providing representative data on the current levels of tritium in drinking water sources near major facilities releasing this radionuclide in Canada. 

This compilation is reasonably comprehensive, but no attempt was made to document every possible criterion in every jurisdiction.A substantive effort was nevertheless made to obtain authoritative criteria directly from all relevant developed countries, through detailed searches of public sources of information, and through correspondence with key regulators when this information was not directly available.The focus of our effort was on countries that operate CANDU and other power reactors, countries of the European Union, and other developed countries with significant releases of tritium.

2.  RADIATION PROTECTION BASIS OF DRINKING WATER GUIDELINES

In most countries, including Canada, the guidelines for radionuclides in drinking water are based on international radiation protection methodologies, including recommendations of the International Commission on Radiological Protection (ICRP) and the World Health Organization (WHO) [ICRP, 1991a; WHO, 2004].A summary table is provided in the Appendix, along with detailed information on guidelines and standards for individual countries.

2.1 International Commission on Radiological Protection (ICRP)

Radiation protection methodologies and principles have been developed by the International Commission on Radiological Protection (ICRP).This body of international experts was established to advance the science of radiological protection for the public benefit.It examines the scientific evidence available and provides recommendations and guidance on all aspects of protection against ionising radiation.These recommendations have been followed closely in establishing the Radiation Protection Regulations under the Canadian Nuclear Safety and Control Act.The ICRP approach is also endorsed and used in most other countries and by international organizations, such as the World Health Organization (WHO), the International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency of the Organization for Economic Cooperation and Development (OECD).

The dose limits recommended by the ICRP for occupational and public exposures are generally adopted by regulators (including the CNSC and Health Canada) for legal purposes, and must not be exceeded under normal circumstances.For members of the public, the ICRP recommends an effective dose limit of 1 mSv for any combination of external and internal doses,received or committed in one year, excluding natural background radiation and medical or therapeutic exposures.The excess lifetime risk from a single exposure to 1 mSv has been estimated to be 7.3 × 10-5 [ICRP, 1991a], or 1 in 14,000.This level of risk includes outcomes such as fatal cancer, severe hereditary effects, and non-fatal cancers weighted for severity and ease of curing.For a lifetime exposure of 1 mSv per year over 70 years, the total risk would be about 5 × 10-3 or 1 in 200 [ICRP, 1991b].

2.2 World Health Organisation (WHO)

The WHO is the directing and coordinating authority for health within the United Nations system.It is responsible for providing leadership on global health matters, shaping the health research agenda, setting norms and standards, articulating evidence-based policy options, providing technical support to countries and monitoring and assessing health trends.

In setting derived guidelines for radionuclides in drinking water, the WHO recognised that water consumption contributes only a portion of the total radiation dose, and that some radionuclides present are natural in origin and therefore cannot be excluded from consideration.Consequently, the WHO guidelines for radionuclides in drinking water have been derived based on a reference dose level (RDL) or effective dose of 0.1 mSv from one year’s consumption of drinking water.This represents 10% of the dose limit for members of the public, as recommended by the ICRP [ICRP, 1991a] and as adopted in the Basic Safety Standards of the International Atomic Energy Agency [IAEA, 1996] and the CNSC’s Radiation Protection Regulations.These principles have been accepted by the WHO and many of its member states, the European Commission, and the Food and Agriculture Organization of the United Nations (FAO).The RDL of 0.1 mSv represents less than 5% of the average annual dose attributable to natural background radiation (i.e., 2.4 mSv).The risk of fatal and weighted non-fatal conditions at a lifetime exposure (i.e. 70 years) of 0.1 mSv per year (1/10th of 1 mSv) is between 10-5 and 10-6 per year, or about 6 × 10-4 over a lifetime or 1 in 1,667 [Health Canada, 1995a].

For each radionuclide, the guideline reference level (GL, also known as the maximum acceptable concentration, MAC, or maximum contaminant level, MCL) for radionuclides in drinking water has generally been calculated using the following equation:

where: 

  GL = guideline reference level of radionuclide in drinking water (Bq/L),

  RDL = reference dose level, equal to 0.1mSv per year,

  DCF = dose conversion factor for ingestion by adults (Sv/Bq),

  q = annual ingested volume of drinking-water.

Most national and international guidelines assume a daily water intake of 2 L, or 730 L/year, and are based on an adult dose conversion factor (DCF) provided by the ICRP [ICRP, 1996].The DCF provides an estimate of the 50-year committed effective dose resulting from a single intake of 1 Bq of a given radionuclide.

The calculation for the GL for tritium would therefore be as follows: 

Higher DCFs for younger age groups (accounting for the higher uptake and/or metabolic rates) do not lead to significantly higher dose criteria, due to the smaller amounts of water consumed.Consequently, the GL based on adult parameters and an RDL of 0.1 mSv per year for one year’s consumption of drinking water can be used for all age groups as a conservative assumption [WHO, 2004].

The guideline reference level (GL) is based on the total activity in a water sample, whether radionuclides appear singly or in combination, and includes the dose due to both natural and artificial radionuclides.Individual GLs therefore apply only in the event that a single radionuclide is found in the water supply.Where two or more radionuclides that affect the same organ or tissue are found to be present in drinking water, the total dose received from all radionuclides should not exceed the guideline reference level of 0.1 mSv per year.

In Canada and elsewhere, actual concentrations of radionuclides, particularly in surface drinking waters, are usually orders of magnitude (e.g. 100-fold) below the GL from the WHO (2004).Water supplies with levels of radioactivity up to the reference level are considered acceptable for consumption.However, the adoption of these guidelines does not imply “lack of action” until concentrations reach the GL.The treatment of water supplies for radionuclides is typically governed by the ALARA principle, i.e. keeping exposures “As Low As Reasonably Achievable”, with economic and social factors taken into consideration.Levels may be further reduced if justified.In cases where a single sample does not meet the guideline, the reference dose would be exceeded only if exposure to the same measured concentration were continued for a full year.Hence, such a sample does not in itself imply that the water is unsuitable for consumption, and should be regarded only as a level at which further investigation, including additional sampling, is needed.[WHO, 2004; Health Canada, 1995b]

3.  REGULATORY APPROACHES

3.1 Application in Canada

In Canada, the quality of drinking water is primarily the responsibility of the provinces and municipalities.The Canadian Guidelines for Canadian Drinking Water Quality [Health Canada, 2007] combine radiological, chemical, and microbiological risk assessment and management practices within a flexible risk control strategy.The Guidelines have been established through the Federal-Provincial-Territorial Committee on Drinking Water (CDW), and are intended to facilitate consistency in drinking water quality across the country.

The Guidelines have been designed to accommodate the diverse needs of the various jurisdictions involved.Although not mandatory, the Guidelines may be used by the provinces and territories as a basis for setting maximum permissible levels for radionuclide, chemical, and microbiological hazards.Since water quality is essentially a provincial responsibility in Canada, the provinces may adopt the Guidelines in whole or in part, or may establish their own criteria.

The Guidelines set the GL of tritium in drinking water at 7,000 Bq/L.

3.2 Application in Canadian Provinces

Several provinces have incorporated the tritium guideline from Health Canada’s Guidelines for Canadian Drinking Water Quality into a provincial drinking water standard; all other provinces do not have prescribed limits for tritium.Information for the provinces that have adopted this value as a standard (Alberta, Manitoba, Ontario and Quebec) is provided in the Appendix.

The Ontario Drinking Water Advisory Council is currently examining the Ontario Drinking Water Quality Standard for tritium at the request of the Ontario Minister of the Environment.In 1994, the Ontario Advisory Committee on Environmental Standards (ACES) submitted the report “A Standard for Tritium. A Recommendation to the Minister of Environment and Energy [of Ontario]”, which recommended an interim guideline of 100 Bq/L for tritium in drinking water.Shortly thereafter, the Ontario Ministry of the Environment (MOE) issued an Interim Ontario Drinking Water Objective for tritium of 7,000 Bq/L based on internationally-recommended radiological protection approaches [MOE, 1994].The Minister of the Environment then requested guidance from Health Canada in regards to the different approaches used within these two documents.

In response, the Joint Working Group 6 (JWG-6) was formed in January 1995, composed of representatives from the Atomic Energy Control Board’s (AECB, replaced by the CNSC in 2000) Advisory Committees on Nuclear Safety (ACNS) and Radiological Protection (ACRP), the Group of Medical Advisors, and Health Canada.

The JWG-6 found that the proposed limits in the ACES report approaching the value of zero risk may not be achievable in any human endeavour.The experts further concluded that the interim risk limit of 100 Bq/L for tritium in drinking water proposed by the ACES study was inconsistent with international regulatory philosophy, which instead supported the MOE’s limit of 7,000 Bq/L.The JWG-6 also studied the estimated lifetime cancer risk from continuous exposure (in drinking water) to maximum acceptable concentrations (MAC) of selected carcinogens, as derived from the Canadian Drinking Water Quality Guidelines.They noted that the risk associated with exposure to carcinogens in drinking water ranged from less than 1 to more than 800 per million, whereas the risk associated with exposure to all radioactive materials combined was 400 per million.The JWG-6 concluded that the risk-management strategy behind the 1995 guidelines provided a high degree of health protection, and the 7,000 Bq/L interim guideline for tritium was formalized as a standard in Ontario Regulation 242/07 [MOE, 2007].

3.3 Application in Other Countries

As mentioned earlier, the guidelines for radionuclides in drinking water of most of the international community are based on a single calculation incorporating international radiation protection recommendations from the ICRP and WHO: 

Different guideline values among most jurisdictions (see Table 2) result from four sources of variation, described in sections 3.3.1 to 3.3.4.

Table 2.International Limits for Tritium in Drinking Water

3.3.1  Variation in RDL (or committed effective dose)

Whereas most countries implement the RDL or committed effective dose of 0.1 mSv recommended by the WHO, a few countries have chosen a different RDL, resulting in a different guideline level when used in the GL equation:

Australia:1 mSv per year=76,103 Bq/L[NHMRC, 2004]
Finland:0.5 mSv per year=30,000 Bq/L[STUK, 1993]
United States:0.04 mSv per year = 740 Bq/L (or 2,253 Bq/L, see variation 3.3.4)

3.3.2  Variation in Rounding Out of the Final Criterion

The GL calculation above results in a value of 7,610 Bq/L.However, this value was rounded in three different ways:the WHO and Switzerland rounded the value up to 10,000 Bq/L, whereas Russia and Canada rounded it out to 7,700 and 7,000 Bq/L, respectively.[WHO, 2004; DFI, 2006; NRB-99; Health Canada, 2007].ISTISAN (2000) reported a value 7,600 Bq/L using only two significant digits.

3.3.3  European Union Special Case

The derivation of a drinking water total indicative dose (TID) criterion (0.1 mSv/year) in the European Union’s (EU) Council Directive on the quality of water intended for human consumption 98/83/EC [EU, 1998] is not explained in the directive or in primary documents prior to the publication of the directive.However, it follows the basic logic of the WHO as outlined in section 2.2. Derived activity concentrations were subsequently calculated after the directive was published, using parameters from the 96/29 EURATOM Directive.The corresponding criterion for an adult is 7,600 Bq/L, with a critical concentration of 6,000 Bq/L for a 1-2 year old [ISTISAN, 2000].The inclusion of criteria for radioactivity in the directive was not part of the initial proposal of the EU Commission [EU, 1995]; these criteria were incorporated during the development of the legislation at the request of the European Parliament.
Following the Opinion of the European Parliament of 12 December 1996, the Council Common Position of 19 December 1997, and the Decision of the European Parliament of 13 May 1998, the EU Commission did not make the requirements for radioactivity mandatory, but only indicative.Tritium was cited as an indicator parametric value at 100 Bq/L, and the total indicative dose was cited as an indicator parametric value of 0.1 mSv/year [ISTISAN, 2000].

The 100 Bq/L parameter is effectively a screening value, providing an indication of the possible presence of other, potentially more harmful, artificial radionuclides discharged into the environment.Both the tritium concentration and the total indicative dose have a similar status, indicating a potential radiological problem when exceeded, and should not be regarded as limit values [ISTISAN, 2000].

For example, in the implementation of these principles in the United Kingdom, if the level of tritium is above 100 Bq/L, further investigation is triggered and action may be required [DWI, 2005].The relevant guidance states:

“Tritium can also be an indication of contamination from artificial sources and water companies should take actions to investigate the source of any exceedence of the indicator value.If the indicator value is exceeded additional analysis should be undertaken to establish which isotopes are present and the total indicative dose calculated from the individual isotope concentrations.If the total indicative dose exceeds the indicator value of 0.10 mSv/year, appropriate medical advice should be sought.The specification for total indicative dose is expressed in terms of the dose over a year.In interpreting the results of radioactivity monitoring it is necessary to take account of the variability in activity levels over time.Some water sources are likely to show seasonal variation due to natural processes.In addition, any short term increase in radionuclides that may result from radiological incidents should be assessed against guidance for food and liquids, within guidance published by the former Department of the Environment (Civil Emergencies involving radioactive substances).”

Most EU member states have transposed the 1998 EU directive into a national law, regulation or standard, and most have followed the logic of using the 100 Bq/L value for tritium only as a screening value (see forms in Appendix).

3.3.4 United States Special Case

The United States (US) did not adopt ICRP risk coefficients and dose limit recommendations in deriving its original – and still current - drinking water standard for tritium.Instead, the United States Environmental Protection Agency (USEPA) used information from 1967 U.S. Vital Statistics, and the Biological Effects of Ionizing Radiation I report [BEIR, 1972], to set the national standard (referred to as a Maximum Contaminant Level or MCL) at 20,000 pCi/L (740 Bq/L) based on a 4 mrem (0.04 mSv) per year dose limit.

Considering the sum of the deposited fallout radioactivity and the additional amounts due to releases from other sources existing in 1967, the USEPA believed that the total dose equivalent from man-made radioactivity was not likely to result in a total body or organ dose to any individual that exceeded 4 mrem/year.Consequently, the USEPA believed that the adoption of the standard would not affect many public water systems, if any.At the same time, the Agency believed that a MCL set at this level would provide adequate public health protection.

In setting the MCLs for man-made beta and photon emitters in 1976 [USEPA, 1976], the USEPA used cancer risk estimates for the U.S. population in 1967 [see USEPA, 2000a and 2000b for a discussion of the 1991 proposed rule].The BEIR I report indicated that the individual risk of fatal cancer from a lifetime total body dose rate of 0.04 mSv per year ranged from about 0.4 to 2 x 10-6 per year (1 in 2,500,000 to 1 in 500,000) depending on whether an absolute or relative risk model was used.Using best estimates from both models for fatal cancer, the USEPA believed that an individual risk of 0.8 x 106 per year (1 in 1,250,000) resulting from a 0.04 mSv annual total body dose was a reasonable estimate of the annual risk from a lifetime ingestion of drinking water.Over a 70-year period, the corresponding lifetime fatal cancer risk would be 5.6 x 10-5 (1 in 17,857), with the risk from the ingestion of water containing less amounts of radioactivity being proportionately smaller [USEPA, 2000b].

Since the time the USEPA developed the 1976 standard, scientists have improved the calculation methods to equate concentrations of tritium in drinking water (pCi/L) to radiation doses in people (mrem).In 1991, the USEPA re-calculated the tritium concentration equal to a dose of 4 mrem from weighted organ-specific dose equivalent values, using weighting factors as specified by the ICRP in 1977/1979, and using metabolically-based dose calculations.With this updated method of calculation, the USEPA found that a dose of 4 mrem (0.04 mSv) per year would equal a tritium concentration of 60,900 pCi/L (2,253 Bq/L) — a threefold increase from the maximum contaminant level of 20,000 pCi/L (740 Bq/L) established in 1976.However, since the older criterion met overall risk management objectives, the USEPA kept the 1976 value of 20,000 pCi/L for tritium in its latest regulations in the final rule [USEPA, 2000a].

A search by CNSC staff of the most populated individual States indicated that most (if not all) States have adopted the USEPA MCLs for drinking water quality.However, in 2006, the Office of Environmental Health Hazard Assessment (OEHHA) in the California Environmental Protection Agency adopted a public health goal (PHG) of 400 pCi/L (14.8 Bq/L) for tritium in drinking water [OEHHA, 2006].PHGs established by OEHHA are not regulatory, and represent only non-mandatory goals.By state and federal law, MCLs established by DHS must be at least as stringent as the federal MCL.PHGs are based solely on scientific and public health considerations, without regard to economic cost considerations or technical feasibility.While the current California maximum contaminant level (MCL) for tritium in drinking water is 20,000 pCi/L (740 Bq/L), the ongoing revision of the California drinking water standards (MCLs) will consider the above-mentioned PHG for tritium in drinking water along with economic factors and technical feasibility.

4. DIFFERENCES BETWEEN CANADIAN AND INTERNATIONAL APPROACHES

In Canada, the guideline reference level (GL), or maximum acceptable concentration (MAC), for tritium in drinking water is 7,000 Bq/L, as described in the Guidelines for Canadian Drinking Water Quality [Health Canada, 2007].Of the many countries researched for the purposes of this compilation, most have based their national standard, regulation or guideline on internationally-accepted radiation protection concepts, including the ICRP’s dose-risk estimations and dose conversion factors, as well as thereference dose level of 0.1 mSv per year adopted by the WHO.Together, these concepts suggest a rounded GL of 7,600 Bq/L.

There are four main exceptions or variations to this approach.

1) Rather than a mandatory parameter, the EU has elected to use a tritium guideline value of 100 Bq/L as a screening parameter for the presence of other, potentially more harmful, artificial radionuclides.

2) Whereas Australia accepts the ICRP concepts mentioned above, it differs from the WHO by adopting a reference dose level of 1 mSv per year rather than 0.1 mSv per year.The result is an Australian national guideline of 76,103 Bq/L.

3) Whereas Finland also accepts the ICRP concepts mentioned above, it differs from the WHO by adopting a reference dose level of 0.5 mSv per year rather than 0.1 mSv per year, and a drinking water intake rate of 2.2 L per day rather than 2 L.Therefore, Finland’s standard for tritium in drinking water is 30,000 Bq/L.

4) The United States calculated its national MCL for tritium in drinking water in 1976 based on former radiological concepts that now differ from current ICRP and WHO opinion, and continues to retain this older criterion on a risk management basis (see section 3.3.4).

5. CURRENT TRITIUM LEVELS IN DRINKING WATER

In Canada, current tritium levels in drinking water are orders of magnitude less than the GL of 7,000 Bq/L near nuclear facilities, and similarly well below the European Union’s GL of 100 Bq/L.To provide a perspective on the data available, representative data are provided in Tables 3 and 4, illustrating recent levels of tritium in drinking water near major nuclear facilities releasing this radionuclide in Canada.

Although no exhaustive search was conducted for all available international information, in developed countries with power reactors such as Belgium [AFCN, 2006], France [IRSN, 2007], Germany [BMU, 2006], and Spain [CSN, 2005], tritium levels in drinking water are also well below each country’s GL of 100 Bq/L.

Table 3.Drinking Water Tritium Concentration near Nuclear Sites

¹ Annual Summary and Assessment of Environmental and Radiological Data for 2006. Bruce Power. 2007.

² Annual Report of Radiological Environmental Monitoring in 2005 at Chalk River Laboratories. AECL. 2006.

³ Centrale nucléaire Gentilly-2. Résultats du programme de surveillance de l’environnement du site de Gentilly. Rapport annuel 2006. Hydro-Québec. 2007.

⁴ Point Lepreau Generating Station. Environmental Monitoring Radiation Data. NB Power. 2007.

⁵ 2006 Results of Radiological Environmental Monitoring Programs. Ontario Power Generation Inc. 2007.

Table 4.Drinking Water Tritium Concentration in Background Locations

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ICRP, International Commission on Radiological Protection, 1991a. 1990 recommendations of the ICRP. Annals of the ICRP, 21(1.3). Oxford, Pergamon Press (Publication 60).

ICRP, International Commission on Radiological Protection, 1991b. 1990 recommendations of the ICRP. Radiological Protection Bulletin 119 (Supplement). National Radiological Protection Board, Chilton, UK.

ICRP, International Commission on Radiological Protection, 1996. Age-dependent doses to members of the public from intake of radionuclides: Part 5. Compilation of ingestion and inhalation dose coefficients. Oxford, Pergamon Press (International Commission on Radiological Protection Publication 72).

ICRP, International Commission on Radiological Protection, 2000. Protection of the public in situations of prolonged radiation exposure. ICRP Publication 82, Pergamon Press, Oxford, United Kingdom.

IRSN, Institut de radioprotection et de sûreté nucléaire (Radioprotection and Nuclear Safety Institute), 2007. Bilan de l’état radiologique de l’environnement français en 2005. France.
http://www.irsn.org/surveillance%5Fenvironnement/index.php?page=BilansSurveillance (accessed on August 28, 2007)

ISTISAN, Istituto Superiore di Sanità, 2000. Council Directive 98/83/EC on the quality of water intended for human consumption: calculation of derived activity concentrations. Italy.
http://dspace.iss.it/dspace/handle/2198/-91045 (accessed on September 07, 2007)

Lokan, K.H., 1998. Drinking water quality in areas dependent on groundwater. Radiation Protection in Australasia(1998) 15 (1), 11–14.

NB Power, 2007. Point Lepreau Generating Station. Environmental Monitoring Radiation Data. New Brunswick, Canada.

NHMRC, National Health and Medical Research Council, 1995. Recommendations for limiting exposure to ionising radiation (1995). Radiation Health Series No. 39, Government Publishing Service, Canberra.

NHMRC, National Health and Medical Research Council, 2004. Australian Drinking Water Guidelines 6. Australia.
www.nhmrc.gov.au/publications/synopses/eh19syn.htm (accessed on August 21, 2007)

NRB-99. Radiation Safety Norms. Russia.
www.wdcb.ru/mining/zakon/NRB99.htm (accessed on August 01, 2007)

OEHHA, Office of Environmental Health Hazard Assessment, 2006. Public Health Goals for Chemicals in Drinking Water ― Tritium. OEHHA, California Environmental Protection Agency, California USA.
www.oehha.ca.gov/ water/phg/pdf/PHGtritium030306.pdf (accessed on September 07, 2007)

MOE, Ontario Ministry of the Environment MOE, 1994. Ontario Drinking Water Objectives. Toronto, Ontario.

MOE, Ontario Ministry of the Environment, 2007. Ontario Regulation 242/07. Ontario Drinking-Water Quality Standards. The Ontario Gazette: June 23, 2007
http://www.e-laws.gov.on.ca/Download?dID=223870 (accessed on August 21, 2007)

OPG, Ontario Power Generation, 2007. 2006 Results of Radiological Environmental Monitoring Programs. Ontario, Canada.
http://www.opg.com/pdf/Nuclear%20Reports%20and%20Publications/2006%20Results%20of%20Environmental%20Monitoring%20Programs.pdf

STUK, Radiation and Nuclear Safety Authority, 1993. Radioactivity of Household Water. ST 12.3. Erweko Paintuote, Helsinki, Finland, 1994.

USEPA, US Environmental Protection Agency, 1976. "Drinking Water Regulations: Radionuclides." Federal Register, Vol. 41, No. 133, pp. 28402–28409, July 9, 1976.

USEPA, US Environmental Protection Agency, 2000a. 40 CFR Parts 9, 141, and 142 National Primary Drinking Water Regulations; Radionuclides; Final Rule. FRL-6909-3, EPA, Cincinnati, OH. www.epa.gov/fedrgstr/EPA-WATER/2000/December/Day-07/w30421.pdf (accessed on August 22, 2007)

USEPA, US Environmental Protection Agency, 2000b. 40 CFR Parts 141 and 142. National Primary Drinking Water Regulations; Radionuclides; Notice of Data Availability; Proposed Rule. FRL-6580-8, EPA, Cincinnati, OH. www.epa.gov/EPA-WATER/2000/April/Day-21/w9654.htm (accessed on August 21, 2007)

WHO, World Health Organisation, 2004. Guidelines for Drinking-Water Quality. Vol.1. Third Edition. Geneva, Switzerland.
www.who.int/water_sanitation_health/dwq/GDWQ2004web.pdf (accessed on August 21, 2007)

APPENDIX

COMPILATION OF TRITIUM GUIDELINES AND STANDARDS 

Introduction 

The following appendix includes a summary table along with forms containing information on the standards or guidelines for tritium in drinking water currently observed by a number of countries (including CANDU owner countries, the members of the G8, representative State members of the EU, and other significant countries) international organisations and Canadian provinces (in alphabetical order).All government and organisation websites were thoroughly searched for relevant legal and regulatory documents.Some information was supplemented by personal communication with relevant officials, where it was feasible.Additional information may be available, but was not obtainable within reasonable effort.

This database is not exhaustive, however it can be considered to be reasonably complete in regards to the major emitters of tritium in the world.The occasional blank spaces in the forms indicate that the relevant information was not accessible.

TABLE A1.
SUMMARY TABLE OF international limits for tritium in drinking water

* Sources:

World Nuclear Association reactor database
http://db.world-nuclear.org/reference/reactorsdb_index.php

CANDU Owners Group website
http://www.candu.org

* Level currently under revision

* Level currently under revision

* 1 operating facility in September 2007

* 1 operating facility in September 2007

* Level currently under revision

Standards and Guidelines for Tritium in Drinking Water (INFO-0766)

DISCLAIMER 

The information contained in this document is not exhaustive, however it can be considered to be reasonably complete in regards to the major emitters of tritium in the world. The information is current as of September 2007.

This factual document does not attempt to analyze the information or draw conclusions.

TABLE OF CONTENTS

• Tables
• Acronyms
• Glossary
• Executive Summary
• 1. Introduction
• 2. Radiation Protection Basis of Drinking Water Guidelines
• 3. Regulatory Approaches
• 4. Differences Between Canadian and International Approaches
• 5. Current Tritium Levels in Drinking Water
• References
• Appendix

TABLES

Table 1. Radiation Units

Table 2. International Limits for Tritium in Drinking Water

Table 3. Drinking Water Tritium Concentration near Nuclear Sites

Table 4. Drinking Water Tritium Concentration in Background Locations

Table A1. Summary Table of International Limits for Tritium in Drinking Water

ACRONYMS 

GLOSSARY 

Table 1.Radiation Units

EXECUTIVE SUMMARY 

• Natural background levels of tritium can be found everywhere in the environment.
• In Canada, the control of tritium releases to the environment is important, since this element is a by-product of CANDU nuclear reactors and is used to produce gaseous tritium light sources.
• The guidelines for radionuclides in drinking water adopted by the majority of the international community are based on international radiation protection methodologies and recommendations of the International Commission on Radiological Protection (ICRP) and the World Health Organization (WHO).
• The European Union, the United States, Australia and Finland use variations of the WHO approach to arrive at differing guideline reference levels.
• In Canada, current tritium levels in drinking water are several orders of magnitude lower than the guideline reference level (GL) of 7,000 Bq/L near nuclear facilities, and similarly well below the European Union’s GL of 100 Bq/L.

1. INTRODUCTION

1.1 Tritium in the Environment

Tritium is a radioactive form of hydrogen with a physical decay half-life of 12.3 years.It emits very low-energy beta radiation, which is completely absorbed by common materials such as sheets of plastic, glass or metal, and cannot penetrate the top dead layer of skin in humans.Exposure can nevertheless pose a risk if the element is ingested in drinking water or food, or inhaled or absorbed through the skin.In Canada, the control of tritium releases to the environment is particularly important, since CANDU reactors produce significantly more tritium than most other types of reactors due to the use of heavy water (deuterium) in the moderator and heat transport system.Tritium is also used by a few industries to produce gaseous tritium light sources.Much smaller quantities are used in research applications, and as a tracer in oil and gas exploration.Tritium also forms naturally in the upper atmosphere due to the continuous bombardment of atmospheric gases by high energy cosmic rays.When it is present either naturally or artificially, tritium may be incorporated into water, thus entering the natural hydrological cycle.Hence, natural background levels of tritium can be found everywhere in the environment, including water, soil, and vegetation.Additional information on the presence and use of tritium in Canada can be found in a recent document produced by the Canadian Nuclear Safety Commission [CNSC, 2007a].

1.2 Regulation of Tritium Releases in Canada

Under the Nuclear Safety and Control Act (NSCA), the mandate of the Canadian Nuclear Safety Commission (CNSC) includes the dissemination of scientific, technical and regulatory information concerning the activities of the CNSC, and the effects on the environment and the health and safety of persons, of the development, production, possession, transport and use of nuclear substances.Under the NSC Act, the CNSC regulates facilities that possess more than 1 GBq (1 x 109 Bq) of tritium.The CNSC regulates potential releases of tritium to the environment through several licensing requirements, including absolute limits on how much tritium can be released on a license-specific basis.This is typically accomplished by imposing quantitative Derived Release Limits (DRL) on tritium entering air or water.These quantities are based on limiting releases to levels less or equal to the prescribed public dose limit of 1 mSv.Current tritium DRLs and amounts actually released relative to these absolute limits are summarized in [CNSC, 2007b].

General requirements for major nuclear facilities licensed by the CNSC include environmental protection policies, programs, and procedures that make adequate provision for protection of the environment.These are typically referred to collectively as an environmental management system, and include two key provisions for the control of releases of radioactivity to the environment: ALARA and Action Levels.ALARA is the paramount requirement for all licensed activities under the Radiation Protection Regulations; according to it, releases must be kept “As Low As Reasonably Achievable”, social and economic factors being taken into account.Action Levels are also required, and are set such that an exceedence may indicate a loss of control.Action levels are typically set for gaseous or liquid effluent concentrations or for activity levels in the environment.Response to an action level includes a thorough investigation of the cause, remedial actions and reporting to the CNSC.In addition, licensees usually establish administrative controls set well below action levels to trigger investigations into potentially unusual operating conditions and their root causes.

The CNSC requires regular reporting of the results of monitoring of routinely-discharged radioactive effluents (including the total activity or total amount released), and, at a minimum, annual reports of environmental monitoring results.Lastly, the CNSC also requires the reporting of any release of a nuclear substance into the environment at a quantity not authorized by the NSC Act, regulations or the license, or any unmeasured release.

1.3  Scope of this Document

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 in the world exercising best practices.In response, CNSC staff initiated a “Tritium Studies” project with several planned information gathering and research activities extending to 2010 (a fact sheet is available at www.nuclearsafety.gc.ca).The objective of this project is to enhance the information available to guide regulatory oversight of tritium processing and tritium releases in Canada.

This present report of drinking water standards and guidelines is a factual report, one of a series of public information documents being produced through the auspices of the Tritium Studies project.Its purpose is threefold:

• to summarize criteria on a national and international basis from readily-available public sources of information, along with the scientific and policy basis underlying these criteria;

• to discuss the Canadian federal drinking water guideline of 7,000 Bq/L relative to criteria or guidance from other jurisdictions; and

• to provide a perspective on the need for any revisions to the existing regulatory approach for tritium by providing representative data on the current levels of tritium in drinking water sources near major facilities releasing this radionuclide in Canada. 

This compilation is reasonably comprehensive, but no attempt was made to document every possible criterion in every jurisdiction.A substantive effort was nevertheless made to obtain authoritative criteria directly from all relevant developed countries, through detailed searches of public sources of information, and through correspondence with key regulators when this information was not directly available.The focus of our effort was on countries that operate CANDU and other power reactors, countries of the European Union, and other developed countries with significant releases of tritium.

2.  RADIATION PROTECTION BASIS OF DRINKING WATER GUIDELINES

In most countries, including Canada, the guidelines for radionuclides in drinking water are based on international radiation protection methodologies, including recommendations of the International Commission on Radiological Protection (ICRP) and the World Health Organization (WHO) [ICRP, 1991a; WHO, 2004].A summary table is provided in the Appendix, along with detailed information on guidelines and standards for individual countries.

2.1 International Commission on Radiological Protection (ICRP)

Radiation protection methodologies and principles have been developed by the International Commission on Radiological Protection (ICRP).This body of international experts was established to advance the science of radiological protection for the public benefit.It examines the scientific evidence available and provides recommendations and guidance on all aspects of protection against ionising radiation.These recommendations have been followed closely in establishing the Radiation Protection Regulations under the Canadian Nuclear Safety and Control Act.The ICRP approach is also endorsed and used in most other countries and by international organizations, such as the World Health Organization (WHO), the International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency of the Organization for Economic Cooperation and Development (OECD).

The dose limits recommended by the ICRP for occupational and public exposures are generally adopted by regulators (including the CNSC and Health Canada) for legal purposes, and must not be exceeded under normal circumstances.For members of the public, the ICRP recommends an effective dose limit of 1 mSv for any combination of external and internal doses,received or committed in one year, excluding natural background radiation and medical or therapeutic exposures.The excess lifetime risk from a single exposure to 1 mSv has been estimated to be 7.3 × 10-5 [ICRP, 1991a], or 1 in 14,000.This level of risk includes outcomes such as fatal cancer, severe hereditary effects, and non-fatal cancers weighted for severity and ease of curing.For a lifetime exposure of 1 mSv per year over 70 years, the total risk would be about 5 × 10-3 or 1 in 200 [ICRP, 1991b].

2.2 World Health Organisation (WHO)

The WHO is the directing and coordinating authority for health within the United Nations system.It is responsible for providing leadership on global health matters, shaping the health research agenda, setting norms and standards, articulating evidence-based policy options, providing technical support to countries and monitoring and assessing health trends.

In setting derived guidelines for radionuclides in drinking water, the WHO recognised that water consumption contributes only a portion of the total radiation dose, and that some radionuclides present are natural in origin and therefore cannot be excluded from consideration.Consequently, the WHO guidelines for radionuclides in drinking water have been derived based on a reference dose level (RDL) or effective dose of 0.1 mSv from one year’s consumption of drinking water.This represents 10% of the dose limit for members of the public, as recommended by the ICRP [ICRP, 1991a] and as adopted in the Basic Safety Standards of the International Atomic Energy Agency [IAEA, 1996] and the CNSC’s Radiation Protection Regulations.These principles have been accepted by the WHO and many of its member states, the European Commission, and the Food and Agriculture Organization of the United Nations (FAO).The RDL of 0.1 mSv represents less than 5% of the average annual dose attributable to natural background radiation (i.e., 2.4 mSv).The risk of fatal and weighted non-fatal conditions at a lifetime exposure (i.e. 70 years) of 0.1 mSv per year (1/10th of 1 mSv) is between 10-5 and 10-6 per year, or about 6 × 10-4 over a lifetime or 1 in 1,667 [Health Canada, 1995a].

For each radionuclide, the guideline reference level (GL, also known as the maximum acceptable concentration, MAC, or maximum contaminant level, MCL) for radionuclides in drinking water has generally been calculated using the following equation:

where: 

  GL = guideline reference level of radionuclide in drinking water (Bq/L),

  RDL = reference dose level, equal to 0.1mSv per year,

  DCF = dose conversion factor for ingestion by adults (Sv/Bq),

  q = annual ingested volume of drinking-water.

Most national and international guidelines assume a daily water intake of 2 L, or 730 L/year, and are based on an adult dose conversion factor (DCF) provided by the ICRP [ICRP, 1996].The DCF provides an estimate of the 50-year committed effective dose resulting from a single intake of 1 Bq of a given radionuclide.

The calculation for the GL for tritium would therefore be as follows: 

Higher DCFs for younger age groups (accounting for the higher uptake and/or metabolic rates) do not lead to significantly higher dose criteria, due to the smaller amounts of water consumed.Consequently, the GL based on adult parameters and an RDL of 0.1 mSv per year for one year’s consumption of drinking water can be used for all age groups as a conservative assumption [WHO, 2004].

The guideline reference level (GL) is based on the total activity in a water sample, whether radionuclides appear singly or in combination, and includes the dose due to both natural and artificial radionuclides.Individual GLs therefore apply only in the event that a single radionuclide is found in the water supply.Where two or more radionuclides that affect the same organ or tissue are found to be present in drinking water, the total dose received from all radionuclides should not exceed the guideline reference level of 0.1 mSv per year.

In Canada and elsewhere, actual concentrations of radionuclides, particularly in surface drinking waters, are usually orders of magnitude (e.g. 100-fold) below the GL from the WHO (2004).Water supplies with levels of radioactivity up to the reference level are considered acceptable for consumption.However, the adoption of these guidelines does not imply “lack of action” until concentrations reach the GL.The treatment of water supplies for radionuclides is typically governed by the ALARA principle, i.e. keeping exposures “As Low As Reasonably Achievable”, with economic and social factors taken into consideration.Levels may be further reduced if justified.In cases where a single sample does not meet the guideline, the reference dose would be exceeded only if exposure to the same measured concentration were continued for a full year.Hence, such a sample does not in itself imply that the water is unsuitable for consumption, and should be regarded only as a level at which further investigation, including additional sampling, is needed.[WHO, 2004; Health Canada, 1995b]

3.  REGULATORY APPROACHES

3.1 Application in Canada

In Canada, the quality of drinking water is primarily the responsibility of the provinces and municipalities.The Canadian Guidelines for Canadian Drinking Water Quality [Health Canada, 2007] combine radiological, chemical, and microbiological risk assessment and management practices within a flexible risk control strategy.The Guidelines have been established through the Federal-Provincial-Territorial Committee on Drinking Water (CDW), and are intended to facilitate consistency in drinking water quality across the country.

The Guidelines have been designed to accommodate the diverse needs of the various jurisdictions involved.Although not mandatory, the Guidelines may be used by the provinces and territories as a basis for setting maximum permissible levels for radionuclide, chemical, and microbiological hazards.Since water quality is essentially a provincial responsibility in Canada, the provinces may adopt the Guidelines in whole or in part, or may establish their own criteria.

The Guidelines set the GL of tritium in drinking water at 7,000 Bq/L.

3.2 Application in Canadian Provinces

Several provinces have incorporated the tritium guideline from Health Canada’s Guidelines for Canadian Drinking Water Quality into a provincial drinking water standard; all other provinces do not have prescribed limits for tritium.Information for the provinces that have adopted this value as a standard (Alberta, Manitoba, Ontario and Quebec) is provided in the Appendix.

The Ontario Drinking Water Advisory Council is currently examining the Ontario Drinking Water Quality Standard for tritium at the request of the Ontario Minister of the Environment.In 1994, the Ontario Advisory Committee on Environmental Standards (ACES) submitted the report “A Standard for Tritium. A Recommendation to the Minister of Environment and Energy [of Ontario]”, which recommended an interim guideline of 100 Bq/L for tritium in drinking water.Shortly thereafter, the Ontario Ministry of the Environment (MOE) issued an Interim Ontario Drinking Water Objective for tritium of 7,000 Bq/L based on internationally-recommended radiological protection approaches [MOE, 1994].The Minister of the Environment then requested guidance from Health Canada in regards to the different approaches used within these two documents.

In response, the Joint Working Group 6 (JWG-6) was formed in January 1995, composed of representatives from the Atomic Energy Control Board’s (AECB, replaced by the CNSC in 2000) Advisory Committees on Nuclear Safety (ACNS) and Radiological Protection (ACRP), the Group of Medical Advisors, and Health Canada.

The JWG-6 found that the proposed limits in the ACES report approaching the value of zero risk may not be achievable in any human endeavour.The experts further concluded that the interim risk limit of 100 Bq/L for tritium in drinking water proposed by the ACES study was inconsistent with international regulatory philosophy, which instead supported the MOE’s limit of 7,000 Bq/L.The JWG-6 also studied the estimated lifetime cancer risk from continuous exposure (in drinking water) to maximum acceptable concentrations (MAC) of selected carcinogens, as derived from the Canadian Drinking Water Quality Guidelines.They noted that the risk associated with exposure to carcinogens in drinking water ranged from less than 1 to more than 800 per million, whereas the risk associated with exposure to all radioactive materials combined was 400 per million.The JWG-6 concluded that the risk-management strategy behind the 1995 guidelines provided a high degree of health protection, and the 7,000 Bq/L interim guideline for tritium was formalized as a standard in Ontario Regulation 242/07 [MOE, 2007].

3.3 Application in Other Countries

As mentioned earlier, the guidelines for radionuclides in drinking water of most of the international community are based on a single calculation incorporating international radiation protection recommendations from the ICRP and WHO: 

Different guideline values among most jurisdictions (see Table 2) result from four sources of variation, described in sections 3.3.1 to 3.3.4.

Table 2.International Limits for Tritium in Drinking Water

3.3.1  Variation in RDL (or committed effective dose)

Whereas most countries implement the RDL or committed effective dose of 0.1 mSv recommended by the WHO, a few countries have chosen a different RDL, resulting in a different guideline level when used in the GL equation:

Australia:1 mSv per year=76,103 Bq/L[NHMRC, 2004]
Finland:0.5 mSv per year=30,000 Bq/L[STUK, 1993]
United States:0.04 mSv per year = 740 Bq/L (or 2,253 Bq/L, see variation 3.3.4)

3.3.2  Variation in Rounding Out of the Final Criterion

The GL calculation above results in a value of 7,610 Bq/L.However, this value was rounded in three different ways:the WHO and Switzerland rounded the value up to 10,000 Bq/L, whereas Russia and Canada rounded it out to 7,700 and 7,000 Bq/L, respectively.[WHO, 2004; DFI, 2006; NRB-99; Health Canada, 2007].ISTISAN (2000) reported a value 7,600 Bq/L using only two significant digits.

3.3.3  European Union Special Case

The derivation of a drinking water total indicative dose (TID) criterion (0.1 mSv/year) in the European Union’s (EU) Council Directive on the quality of water intended for human consumption 98/83/EC [EU, 1998] is not explained in the directive or in primary documents prior to the publication of the directive.However, it follows the basic logic of the WHO as outlined in section 2.2. Derived activity concentrations were subsequently calculated after the directive was published, using parameters from the 96/29 EURATOM Directive.The corresponding criterion for an adult is 7,600 Bq/L, with a critical concentration of 6,000 Bq/L for a 1-2 year old [ISTISAN, 2000].The inclusion of criteria for radioactivity in the directive was not part of the initial proposal of the EU Commission [EU, 1995]; these criteria were incorporated during the development of the legislation at the request of the European Parliament.
Following the Opinion of the European Parliament of 12 December 1996, the Council Common Position of 19 December 1997, and the Decision of the European Parliament of 13 May 1998, the EU Commission did not make the requirements for radioactivity mandatory, but only indicative.Tritium was cited as an indicator parametric value at 100 Bq/L, and the total indicative dose was cited as an indicator parametric value of 0.1 mSv/year [ISTISAN, 2000].

The 100 Bq/L parameter is effectively a screening value, providing an indication of the possible presence of other, potentially more harmful, artificial radionuclides discharged into the environment.Both the tritium concentration and the total indicative dose have a similar status, indicating a potential radiological problem when exceeded, and should not be regarded as limit values [ISTISAN, 2000].

For example, in the implementation of these principles in the United Kingdom, if the level of tritium is above 100 Bq/L, further investigation is triggered and action may be required [DWI, 2005].The relevant guidance states:

“Tritium can also be an indication of contamination from artificial sources and water companies should take actions to investigate the source of any exceedence of the indicator value.If the indicator value is exceeded additional analysis should be undertaken to establish which isotopes are present and the total indicative dose calculated from the individual isotope concentrations.If the total indicative dose exceeds the indicator value of 0.10 mSv/year, appropriate medical advice should be sought.The specification for total indicative dose is expressed in terms of the dose over a year.In interpreting the results of radioactivity monitoring it is necessary to take account of the variability in activity levels over time.Some water sources are likely to show seasonal variation due to natural processes.In addition, any short term increase in radionuclides that may result from radiological incidents should be assessed against guidance for food and liquids, within guidance published by the former Department of the Environment (Civil Emergencies involving radioactive substances).”

Most EU member states have transposed the 1998 EU directive into a national law, regulation or standard, and most have followed the logic of using the 100 Bq/L value for tritium only as a screening value (see forms in Appendix).

3.3.4 United States Special Case

The United States (US) did not adopt ICRP risk coefficients and dose limit recommendations in deriving its original – and still current - drinking water standard for tritium.Instead, the United States Environmental Protection Agency (USEPA) used information from 1967 U.S. Vital Statistics, and the Biological Effects of Ionizing Radiation I report [BEIR, 1972], to set the national standard (referred to as a Maximum Contaminant Level or MCL) at 20,000 pCi/L (740 Bq/L) based on a 4 mrem (0.04 mSv) per year dose limit.

Considering the sum of the deposited fallout radioactivity and the additional amounts due to releases from other sources existing in 1967, the USEPA believed that the total dose equivalent from man-made radioactivity was not likely to result in a total body or organ dose to any individual that exceeded 4 mrem/year.Consequently, the USEPA believed that the adoption of the standard would not affect many public water systems, if any.At the same time, the Agency believed that a MCL set at this level would provide adequate public health protection.

In setting the MCLs for man-made beta and photon emitters in 1976 [USEPA, 1976], the USEPA used cancer risk estimates for the U.S. population in 1967 [see USEPA, 2000a and 2000b for a discussion of the 1991 proposed rule].The BEIR I report indicated that the individual risk of fatal cancer from a lifetime total body dose rate of 0.04 mSv per year ranged from about 0.4 to 2 x 10-6 per year (1 in 2,500,000 to 1 in 500,000) depending on whether an absolute or relative risk model was used.Using best estimates from both models for fatal cancer, the USEPA believed that an individual risk of 0.8 x 106 per year (1 in 1,250,000) resulting from a 0.04 mSv annual total body dose was a reasonable estimate of the annual risk from a lifetime ingestion of drinking water.Over a 70-year period, the corresponding lifetime fatal cancer risk would be 5.6 x 10-5 (1 in 17,857), with the risk from the ingestion of water containing less amounts of radioactivity being proportionately smaller [USEPA, 2000b].

Since the time the USEPA developed the 1976 standard, scientists have improved the calculation methods to equate concentrations of tritium in drinking water (pCi/L) to radiation doses in people (mrem).In 1991, the USEPA re-calculated the tritium concentration equal to a dose of 4 mrem from weighted organ-specific dose equivalent values, using weighting factors as specified by the ICRP in 1977/1979, and using metabolically-based dose calculations.With this updated method of calculation, the USEPA found that a dose of 4 mrem (0.04 mSv) per year would equal a tritium concentration of 60,900 pCi/L (2,253 Bq/L) — a threefold increase from the maximum contaminant level of 20,000 pCi/L (740 Bq/L) established in 1976.However, since the older criterion met overall risk management objectives, the USEPA kept the 1976 value of 20,000 pCi/L for tritium in its latest regulations in the final rule [USEPA, 2000a].

A search by CNSC staff of the most populated individual States indicated that most (if not all) States have adopted the USEPA MCLs for drinking water quality.However, in 2006, the Office of Environmental Health Hazard Assessment (OEHHA) in the California Environmental Protection Agency adopted a public health goal (PHG) of 400 pCi/L (14.8 Bq/L) for tritium in drinking water [OEHHA, 2006].PHGs established by OEHHA are not regulatory, and represent only non-mandatory goals.By state and federal law, MCLs established by DHS must be at least as stringent as the federal MCL.PHGs are based solely on scientific and public health considerations, without regard to economic cost considerations or technical feasibility.While the current California maximum contaminant level (MCL) for tritium in drinking water is 20,000 pCi/L (740 Bq/L), the ongoing revision of the California drinking water standards (MCLs) will consider the above-mentioned PHG for tritium in drinking water along with economic factors and technical feasibility.

4. DIFFERENCES BETWEEN CANADIAN AND INTERNATIONAL APPROACHES

In Canada, the guideline reference level (GL), or maximum acceptable concentration (MAC), for tritium in drinking water is 7,000 Bq/L, as described in the Guidelines for Canadian Drinking Water Quality [Health Canada, 2007].Of the many countries researched for the purposes of this compilation, most have based their national standard, regulation or guideline on internationally-accepted radiation protection concepts, including the ICRP’s dose-risk estimations and dose conversion factors, as well as thereference dose level of 0.1 mSv per year adopted by the WHO.Together, these concepts suggest a rounded GL of 7,600 Bq/L.

There are four main exceptions or variations to this approach.

1) Rather than a mandatory parameter, the EU has elected to use a tritium guideline value of 100 Bq/L as a screening parameter for the presence of other, potentially more harmful, artificial radionuclides.

2) Whereas Australia accepts the ICRP concepts mentioned above, it differs from the WHO by adopting a reference dose level of 1 mSv per year rather than 0.1 mSv per year.The result is an Australian national guideline of 76,103 Bq/L.

3) Whereas Finland also accepts the ICRP concepts mentioned above, it differs from the WHO by adopting a reference dose level of 0.5 mSv per year rather than 0.1 mSv per year, and a drinking water intake rate of 2.2 L per day rather than 2 L.Therefore, Finland’s standard for tritium in drinking water is 30,000 Bq/L.

4) The United States calculated its national MCL for tritium in drinking water in 1976 based on former radiological concepts that now differ from current ICRP and WHO opinion, and continues to retain this older criterion on a risk management basis (see section 3.3.4).

5. CURRENT TRITIUM LEVELS IN DRINKING WATER

In Canada, current tritium levels in drinking water are orders of magnitude less than the GL of 7,000 Bq/L near nuclear facilities, and similarly well below the European Union’s GL of 100 Bq/L.To provide a perspective on the data available, representative data are provided in Tables 3 and 4, illustrating recent levels of tritium in drinking water near major nuclear facilities releasing this radionuclide in Canada.

Although no exhaustive search was conducted for all available international information, in developed countries with power reactors such as Belgium [AFCN, 2006], France [IRSN, 2007], Germany [BMU, 2006], and Spain [CSN, 2005], tritium levels in drinking water are also well below each country’s GL of 100 Bq/L.

Table 3.Drinking Water Tritium Concentration near Nuclear Sites

¹ Annual Summary and Assessment of Environmental and Radiological Data for 2006. Bruce Power. 2007.

² Annual Report of Radiological Environmental Monitoring in 2005 at Chalk River Laboratories. AECL. 2006.

³ Centrale nucléaire Gentilly-2. Résultats du programme de surveillance de l’environnement du site de Gentilly. Rapport annuel 2006. Hydro-Québec. 2007.

⁴ Point Lepreau Generating Station. Environmental Monitoring Radiation Data. NB Power. 2007.

⁵ 2006 Results of Radiological Environmental Monitoring Programs. Ontario Power Generation Inc. 2007.

Table 4.Drinking Water Tritium Concentration in Background Locations

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APPENDIX

COMPILATION OF TRITIUM GUIDELINES AND STANDARDS 

Introduction 

The following appendix includes a summary table along with forms containing information on the standards or guidelines for tritium in drinking water currently observed by a number of countries (including CANDU owner countries, the members of the G8, representative State members of the EU, and other significant countries) international organisations and Canadian provinces (in alphabetical order).All government and organisation websites were thoroughly searched for relevant legal and regulatory documents.Some information was supplemented by personal communication with relevant officials, where it was feasible.Additional information may be available, but was not obtainable within reasonable effort.

This database is not exhaustive, however it can be considered to be reasonably complete in regards to the major emitters of tritium in the world.The occasional blank spaces in the forms indicate that the relevant information was not accessible.

TABLE A1.
SUMMARY TABLE OF international limits for tritium in drinking water

* Sources:

World Nuclear Association reactor database
http://db.world-nuclear.org/reference/reactorsdb_index.php

CANDU Owners Group website
http://www.candu.org