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

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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 information or draw conclusions.

Table of contents


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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


TermDefinition
ACES Advisory Committee on Environmental Standards
ACNS Advisory Committee on Nuclear Safety
ACRP Advisory Committee on Radiological Protection
AECB Atomic Energy Control Board
ALARA as low as reasonably achievable
BEIR I Biological Effects of Ionizing Radiation
CDW Federal-Provincial-Territorial Committee on Drinking Water
CNSC Canadian Nuclear Safety Commission
DCF dose conversion factor
DRL derived release limit
EU European Union
FAO Food and Agriculture Organization (of the United Nations)
GL guideline reference level
IAEA International Atomic Energy Agency
ICRP International Commission on Radiological Protection
JWG-6 Joint Working Group 6
MAC maximum acceptable concentration
MCL maximum contaminant level
MOE Ministry of the Environment (of Ontario)
NSC Act Nuclear Safety and Control Act
OECD Organization for Economic Cooperation and Development
OEHHA Office of Environmental Health Hazard Assessment
PHG public health goal
RDL reference dose level
TID total indicative dose
USEPA United States Environmental Protection Agency
WHO World Health Organisation

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Glossary

TermDefinition
ALARA Principle for radiation protection, according to which exposures are kept as low as reasonably achievable, while the social and economic factors being taken into account.
Becquerel Unit of activity, the rate at which transformations occur in a radioactive substance. 1 Bq = 1 transformation or disintegration per second. See Table 1.
Committed effective dose Effective dose that will be accumulated over a period of time, effective dose following a single intake of radioactive material into the body. Standard periods of integration are 50 years for adults and 70 years for a lifetime exposure. Unit: Sievert, symbol Sv. See Table 1.
Dose conversion factor Converts an intake of a given radionuclide, in Becquerels, to effective dose, in sieverts
Drinking water Water intended for human consumption.
Effective dose Measure of dose designed to reflect the amount of radiation detriment likely to result from the dose. Unit: Sievert, symbol Sv. See Table 1.
Guideline Highest recommended concentration of a contaminant in drinking reference level water guidelines. Synonyms: maximum acceptable concentration, maximum contaminant level.
Maximum acceptable concentration Highest acceptable concentration of a contaminant in the Guidelines for Canadian Drinking Water Quality. Synonyms: guideline reference level, maximum contaminant level.
Maximum contaminant level Highest acceptable concentration of a contaminant in the United States’ National Primary Drinking Water Regulations. Synonyms: guideline reference level, maximum acceptable concentration.
Radionuclide Unstable nuclide that emits ionising radiation.

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Table 1. Radiation units
Quantity  Old unit  Symbol  SI unit Symbol  Relationship 

Activity 

Curie 

Ci 

Becquerel 

Bq 

1 Ci = 3.7 x 1010 Bq

(Committed) Effective dose 

rem 

rem 

Sievert 

Sv 

1 rem = 0.01 Sv 

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 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 Nuclear Safety and Control Act (NSCA), 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 NSCA, regulations or the license, or any unmeasured release.

1.3 Scope of this document

In January 2007, the Commission 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

  • 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 substantial 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.

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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 percent 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 percent 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:

Maximum acceptable concentration formula as described in the text below

GL = DCF times q divided by RDL.

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: 

Maximum acceptable concentration formula for tritium as described in the text below

GL = 730 litres per year times 1.8 times 10 to the negative power of 11 sieverts/becquerels divided by 1 times 10 to the negative power of 4 sieverts per year equalling 7610 becquerel litres.

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]


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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 Québec) 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: 

Maximum acceptable concentration formula as described in the text below

GL = DCF times q divided by RDL.

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
  Power reactors Tritium limit (Bq/L)
  CANDU Total

Canada 

18 

18 

7,000

EU 

126 

100

Finland 

30,000

Australia 

76,103 

Russia 

31 

7,700

Switzerland 

10,000

United States 

103 

740 

WHO 

n/a 

n/a 

10,000

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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).

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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 an 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.

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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).

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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

Water Source 

Province 

Source 

Distance from site 

Tritium level (Bq/L) 

Kincardine 

Ontario 

Bruce Power

15 km SSW of Bruce B 

6.4 

Port Elgin 

Ontario 

Bruce Power1

17 km NE of Bruce A 

17.4 

Southampton 

Ontario 

Bruce Power1

22 km NE of Bruce A 

12.0 

Local deep wells 

Ontario 

Bruce Power1

Local to Bruce 

<5.9 - 19.1 

Local shallow wells 

Ontario 

Bruce Power1

Local to Bruce 

12.3 - 58.2 

Rolphton 

Ontario 

Chalk River Laboratories

28 km upstream of CRL 

3.0 

Deep River 

Ontario 

Chalk River Laboratories2

9 km upstream of CRL 

3.0 

Chalk River Laboratories 

Ontario 

Chalk River Laboratories2

CRL intake well 

11.0 

Highview 

Ontario 

Chalk River Laboratories2

8 km downstream of CRL 

<15.0 

Harrington Bay 

Ontario 

Chalk River Laboratories2

9 km downstream of CRL 

8.0 

Fort William 

Ontario 

Chalk River Laboratories2

14 km downstream of CRL 

7.0 

Petawawa 

Ontario 

Chalk River Laboratories2

18 km downstream of CRL 

7.0 

Pembroke 

Ontario 

Chalk River Laboratories2

28 km downstream of CRL 

7.0 

Champlain 

Québec 

Hydro-Québec (Gentilly)

 

< 18 

Gentilly 

Québec 

Hydro-Québec (Gentilly)3

 

< 18 

Trois-Rivières 

Québec 

Hydro-Québec (Gentilly)3

 

< 18 

Dipper Harbour 

New Brunswick 

NB Power

28 Ridge Rd, Dipper Harbour 

15.0 

Dipper Harbour

New Brunswick 

NB Power4

22 Ridge Rd, Dipper Harbour 

24.5 

Dipper Harbour 

New Brunswick 

NB Power4

16 Ridge Rd, Dipper Harbour 

20.0 

Dipper Harbour 

New Brunswick 

NB Power4

10 Ridge Rd, Dipper Harbour 

19.0 

Dipper Harbour 

New Brunswick 

NB Power4

4 Ridge Rd, Dipper Harbour 

18.0 

Maces Bay 

New Brunswick 

NB Power4

68 Ridge Rd, Maces Bay 

14.0 

Maces Bay 

New Brunswick 

NB Power4

190 Welch Cove Rd, Maces Bay 

39.0 

Maces Bay 

New Brunswick 

NB Power4

181 Ridge Rd, Maces Bay 

32.5 

Maces Bay 

New Brunswick 

NB Power4

132 Ridge Rd, Maces Bay 

22.5 

Water Source 

Province 

Source 

Distance from Site 

Tritium level (Bq/L) 

Bowmanville 

Ontario 

Ontario Power Generation

7 km ENE of Darlington 

6.0 

Newcastle 

Ontario 

Ontario Power Generation5

13 km E of Darlington 

5.8 

Oshawa 

Ontario 

Ontario Power Generation5

8 km W of Darlington 

7.1 

Local water wells 

Ontario 

Ontario Power Generation5

Local to Darlington 

<1.9 - 21.6 

Ajax 

Ontario 

Ontario Power Generation5

5 km ENE of Pickering 

6.1 

Scarborough Horgan 

Ontario 

Ontario Power Generation5

11 km SW of Pickering 

5.1 

Toronto Harris 

Ontario 

Ontario Power Generation5

22 km WSW of Pickering 

5.1 

Whitby 

Ontario 

Ontario Power Generation5

12 km ENE of Pickering 

6.4 

Local water wells (range) 

Ontario 

Ontario Power Generation5

Local to Pickering 

<1.9 - 114.7 

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

Water source 

Province 

Source 

Tritium level (Bq/L)

Bancroft 

Ontario 

Bruce Power

<3.7 

Bancroft 

Ontario 

Ontario Power Generation

<1.9 

Belleville 

Ontario 

Bruce Power1

4.2 

Belleville 

Ontario 

Ontario Power Generation5

2.6 

Brockville 

Ontario 

Bruce Power1

4.6 

Brockville 

Ontario 

Ontario Power Generation5

3.9 

Burlington 

Ontario 

Bruce Power1

6.0 

Burlington 

Ontario 

Ontario Power Generation5

3.3 

Coburg 

Ontario 

Bruce Power1

5.3 

Coburg 

Ontario 

Ontario Power Generation5

4.8 

Drummondville 

Québec 

Hydro-Québec (Gentilly)3

< 18 

Goderich 

Ontario 

Bruce Power1

5.2 

Goderich 

Ontario 

Ontario Power Generation5

4.5 

Kingston 

Ontario 

Bruce Power1

4.6 

Kingston 

Ontario 

Ontario Power Generation5

3.6 

London 

Ontario 

Bruce Power1

3.7 

London 

Ontario 

Ontario Power Generation5

2.5 

Niagara Falls 

Ontario 

Bruce Power1

4.1 

Niagara Falls 

Ontario 

Ontario Power Generation5

2.7 

North Bay 

Ontario 

Bruce Power1

<3.7 

North Bay 

Ontario 

Ontario Power Generation5

<1.9 

Orangeville 

Ontario 

Bruce Power1

<3.7 

Orangeville 

Ontario 

Ontario Power Generation5

<1.9 

Parry Sound 

Ontario 

Bruce Power1

<3.7 

Parry Sound 

Ontario 

Ontario Power Generation5

2.0 

Sarnia 

Ontario 

Bruce Power1

4.0 

Sarnia 

Ontario 

Ontario Power Generation5

4.0 

St. Catharines 

Ontario 

Bruce Power1

3.7 

St. Catharines 

Ontario 

Ontario Power Generation5

2.9 

Sudbury 

Ontario 

Bruce Power1

5.8 

Sudbury 

Ontario 

Ontario Power Generation5

2.9 

Thunder Bay 

Ontario 

Bruce Power1

<3.7 

Thunder Bay 

Ontario 

Ontario Power Generation5

<1.9 

Windsor 

Ontario 

Bruce Power1

5.2 

Windsor 

Ontario 

Ontario Power Generation5

4.6 

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References

ACES, Ontario Advisory Committee on Environmental Standards, 1994. A Standard for Tritium. A Recommendation to the Minister of Environment and Energy. Report 94-01. Ontario, Canada.

AECL, Atomic Energy of Canada Limited, 2006. Annual Report of Radiological Environmental Monitoring in 2005 at Chalk River Laboratories. AECL. Ontario, Canada.

AFCN, Agence fédérale de Contrôle nucléaire (Federal Nuclear Control Agency), 2006. Surveillance radiologique de la Belgique – Rapport de synthèse 2005. Bruxelles, Belgique (in French).

BEIR Committee, Advisory Committee on the Biological Effects of Ionising Radiation, 1972. BEIR-I: The effects on populations of exposure to low levels of ionising radiation. Division of Medical Sciences, the National Academy of Sciences, National Research Council, Washington, D.C. (Generally known as the BEIR Report)

BMU, Bundesamt für Strahlenschutz (Federal Office for Radiation Protection), 2006. Environmental Radioactivity and Radiation Exposure ― Annual Report 2005 (Jahresbericht 2005). BMU, Bonn, Germany (in German).

Bruce Power, 2007. Annual Summary and Assessment of Environmental Radiological Data for 2006. Ontario, Canada (accessed on August 28, 2007)

CSN, Consejo de seguridad nuclear (Nuclear Security Council), 2005. Environmental Radiological Monitoring Programs – 2004 Results. CSN. Madrid, Spain (in Spanish).

CNSC, Canadian Nuclear Safety Commission, 2007a. A technical briefing to the Commission on Tritium. Commission Member Document 07-M34, Commission Meeting of September 12, 2007. Canadian Nuclear Safety Commission, Ottawa, Canada (available on request from the CNSC).

CNSC, Canadian Nuclear Safety Commission, 2007b. Tritium Releases and Dose Consequences in Canada. Canadian Nuclear Safety Commission, Ottawa, Canada (currently in development)

DFI, Département fédéral de l’intérieur (Federal Department of the Interior), 2006. Ordonnance du DFI sur les substances étrangères et les composants dans les denrées alimentaires (817.021.23). Switzerland (in French).

DWI, Drinking Water Inspectorate, 2005. Guidance on the Water Supply (Water Quality) Regulations 2000 and 2001. United Kingdom.

EU, European Union, 1995. Proposal for a Council Directive on the quality of water intended for human consumption, Commission of the European Communities, COM 94/612-final, Brussels 04 01 1995, 950010 (SYN), 52 pp.

EU, European Union, 1998. Council Directive 98/83/EC on the quality of water intended for human consumption. Official Journal of the European Communities.

Health Canada, 1995a. Approach to the Derivation of Drinking Water Guidelines. Health Canada, Ottawa, Canada.

Health Canada, 1995b. Radiological characteristics. Health Canada, Ottawa, Canada.

Health Canada, 2006. Radiological characteristics of Drinking Water. Document for Public Comment. Health Canada, Ottawa, Canada.

Health Canada, 2007. Guidelines for Canadian Drinking Water Quality. Health Canada, Ottawa, Canada.

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

IAEA, International Atomic Energy Agency (1996). International basic safety standards for protection against ionizing radiation and for the safety of radiation sources. Vienna, Austria.

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.

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.

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.

OEHHA, Office of Environmental Health Hazard Assessment, 2006. Public Health Goals for Chemicals in Drinking Water – Tritium. OEHHA, California Environmental Protection Agency, California USA.

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

OPG, Ontario Power Generation, 2007. 2006 Results of Radiological Environmental Monitoring Programs. Ontario, Canada.

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.

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.

WHO, World Health Organisation, 2004. Guidelines for Drinking-Water Quality. Vol.1. Third Edition. Geneva, Switzerland.

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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

   

Power reactors*

Information obtained

Tritium limit (Bq/L)

   

CANDU

Total

CANDU Owners

Canada

18

18

yes

7,000

 

- Alberta

0

0

yes

7,000

 

- Manitoba

0

0

yes

7,000

 

- N. Brunswick

1

1

yes

none

 

- Ontario

16

16

yes

7,000

 

- Québec

1

1

yes

7,000

 

India

15

17

no

n/a

 

Republic of Korea

4

20

partly

none

 

Romania

2

2

yes

100

 

China

2

10

yes

none

 

Argentina

1

12

partly

none

 

Pakistan

1

2

no

n/a

           

European
Union

Total

2

126

yes

100

Belgium

0

7

yes

100

Finland

0

4

>

yes

30,000

France

0

59

yes

100

Germany

0

17

yes

100

Italy

0

0

yes

100

Northern Ireland

0

0

yes

100

Scotland

0

2

yes

100

Spain

0

8

yes

100

Sweden

0

10

yes

100

United Kingdom

0

19

yes

100

           

Other

Australia

0

0

yes

76,103

Japan

0

53

partly

none

Norway

0

0

yes

100

Russia

0

31

partly

7,700

Switzerland

0

5

yes

10,000

United States

0

103

yes

740

- California

0

4

yes

740

WHO

n/a

n/a

yes

10,000

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* Sources:

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

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


Jurisdiction
Alberta
Tritium limit in drinking water
7,000 Bq/L
Committed effective dose
0.1 mSv/year
Additional considerations
The sum of the committed effective doses from all radionuclides is not to exceed 0.1 mSv/year.
Exact / Rounded
Rounded down to the nearest 1,000
Scope
Provincial
Policy point of origin
Guidelines for Canadian Drinking Water Quality
Legal standard / Guideline
Standard
Year of adoption
2003
Technical / legal reference(s)

Potable Water Regulation, Alta. Reg. 277/2003
http://www.canlii.org/ab/laws/regu/
2003r.277/20070717/whole.html

Standards and Guidelines for Municipal Waterworks, Wastewater and Storm Drainage Systems
http://environment.gov.ab.ca/info/
posting.asp?assetid=6979&categoryid=5

Enforcement
Alberta Environment is responsible for enforcement, as per the regulation and standards mentioned above
Consequences of exceeding limit
 
Target population:
 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes
Applicability
 
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year
Comment

MAC (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L, rounded down to 7,000

Safety factor
A recommended reference dose level (RDL) of the committed effective dose, equal to 0.1 mSv from 1 year’s consumption of drinking water (from the possible total radioactive contamination of the annual drinking water consumption). This comprises 10 percent of the intervention exemption level recommended by the ICRP for dominant commodities (e.g., food and drinking-water) for prolonged exposure situations, which is most relevant to long-term consumption of drinking water by the public (ICRP, 2000). The RDL of 0.1 mSv is also equal to 10 percent of the dose limit for members of the population, recommended by both the ICRP (1991) and the International Basic Safety Standards (IAEA, 1996).
Context :
 
CANDU reactors
0
Total power reactors
0
Research centres
0
Tritium light manufacturing
0
General comments

When two or more radionuclides are found in drinking water, the following relationship should be satisfied:

  C1/MAC1  +  C2/MAC2  + …Ci/MACi    ≤1

where Ci and MACi are the observed and maximum acceptable concentrations, respectively, for each contributing radionuclide.

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Jurisdiction

Argentina

Tritium limit in drinking water

No guideline or standard

Reference value of 10,000 Bq/L from the WHO, used on a case-by-case basis

Committed effective dose

0.1 mSv/year

Additional considerations

 

Exact / Rounded

 

Scope

 

Policy point of origin

 

Legal standard / Guideline

Argentine Food Code (Law 18.284)
http://www.anmat.gov.ar/alimentos/normativas_alimentos_caa.asp (in Spanish)
Standards do not include radioactivity

Year of adoption

 

Technical / legal reference(s)

Personal communication with the Nuclear Regulatory Authority Argentina (July 31, 2007)

Enforcement

 

Consequences of exceeding limit

 

Target population:

All ages and sexes

Urban

Rural

 

Applicability

 
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year)  / 
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L, rounded up to 10,000

Safety factor

 
Context:
 
CANDU reactors
1
Total power reactors
2

Research centres

Tritium light manufacturing


General comments

 

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Jurisdiction

Australia

Tritium limit in drinking water

1 mSv/year (76,103 Bq/L)

Committed effective dose

1 mSv/year

Additional considerations

 

Exact / Rounded

Exact

Scope

National

Policy point of origin

ICRP 1991; 2000

Legal standard / Guideline

Guideline

Year of adoption

2003

Technical / legal reference(s)

Australian Drinking Water Guidelines 6
http://www.nhmrc.gov.au/guidelines-publications/eh52

Enforcement

Enforced at the State and Terrritorial level

Consequences of exceeding limit

Summary of operational responses:

Dose level response (mSv per year)

< 0.5
1. Continue routine monitoring.

0.5–1
1. Consult with relevant health authority.

2. Review frequency of ongoing sampling.

3. Evaluate operational options to reduce exposure.

>1–10
1. Consult with relevant health authorities.

2. Assess in detail possible remedial actions, taking into account potential health impacts and cost effectiveness of actions.

3. Implement appropriate remedial action on the basis of the cost-benefit evaluation.

> 10 1. Water not suitable for consumption on the basis of radioactivity levels.

2. Consult with relevant health authorities.

3. Immediate intervention is expected and remedial action must be taken to reduce doses to below the guideline value of 1.0 mSv.

Target population:

 
All ages and sexes
No : Reference man = 70 kg
Urban
Yes
Rural
Yes

Applicability

Drinking water is defined as water intended primarily for human consumption, either directly, as supplied from the tap, or indirectly, in beverages, ice or foods prepared with water. Drinking water is also used for other domestic purposes such as bathing and showering.

With the exception of bottled or packaged water, the ADWG apply to any water intended for drinking irrespective of the source (municipal supplies, rainwater tanks, bores etc) or where it is consumed (the home, restaurants, camping areas, shops etc).

This guideline deals only with situations where the radionuclide concentrations arise either from natural sources or, more rarely, as the result of past practices (such as abandoned mining operations). It specifically does not apply to situations where the radionuclides arise from current practices under regulatory control, such as an operating uranium mine. Therefore, the guideline should not be used to support an increase in the radionuclide concentrations of drinking water as a result of an operation, on the grounds that the overall dose levels remain below 1 mSv per year.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
1 mSv/year

Comment

Annual dose (mSv/year) =
DCF x water consumption x radionuclide concentration
(mSv/Bq) x (litres/year) x (Bq/L)

Safety factor

The ICRP recommended that, for commodities that are essential for normal living and are amenable to intervention, an individual dose of approximately 1 mSv per year is an acceptable intervention exemption level (ICRP 2000). This is consistent with the recommendation of the NHMRC (1995) of a public exposure limit for practices of 1 mSv per year from all sources. Furthermore, Lokan (1998) concluded that a value of 1 mSv per year might be appropriate as a default action level above which some corrective action will be necessary.

Based on the above, it is recommended that a guideline dose of 1 mSv per year should be applied for radioactivity in drinking water.

Context :

 

CANDU reactors
0
Total power reactors
0
Research centres
2
Tritium light manufacturing
0

General comments

The total estimated dose per year from all radionuclides in drinking water, excluding the dose from potassium-40, should not exceed 1.0 mSv.

The ICRP (1991) estimates the lifetime risk of a fatal cancer resulting from exposure to radiation to be 5 x 10-2 per Sv of radiation dose, that is, five additional fatal cancers for every 100 people exposed per year. Based on this estimate, a dose of 1 mSv per year gives an annual risk of 5 x 10-5, that is, about five additional fatal cancers per 100,000 people exposed per year.

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Jurisdiction

Belgium

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

National

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

Guideline

Year of adoption

1998

Technical / legal reference(s)

« Surveillance radiologique de la Belgique - Rapport de synthèse 2005 »
http://fanc.fgov.be/download/Rapport
%20SRT%202005%20FR.pdf

Enforcement

None. EU Directive 98/83/EC not yet transposed into law.

Consequences of exceeding limit

n/a

Target population :

 

All ages and sexes
No: Adult dose conversion factor, applies to adults and children over 10 years old
Urban
Yes
Rural
Yes

Applicability

As defined in the EU Directive 98/83/EC:

‘Water intended for human consumption’ shall mean:

(a) all water either in its original state or after treatment, intended for drinking, cooking, food preparation or other domestic purposes, regardless of its origin and whether it is supplied from a distribution network, from a tanker, or in bottles or containers;

(b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form;

Exclusion:

(a) natural mineral waters recognised as such by the competent national authorities, in accordance with Council Directive 80/777/EEC of 15 July 1980 on the approximation of the laws of the Member States relating to the exploitation and marketing of natural mineral waters (1);

(b) waters which are medicinal products within the meaning of Council Directive 65/65/EEC of 26 January 1965 on the approximation of provisions laid down by law, regulation or administrative action relating to medicinal products (2).

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 

CANDU reactors
0
Total power reactors
7
Research centres
5
Tritium light manufacturing
0

General comments

See WHO comments.

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Jurisdiction

California

Tritium limit in drinking water

740 Bq/L* (20,000 pCi/L)

Committed effective dose

4 mrem/year (0.04 mSv/year)

Additional considerations

If two or more radionuclides are present, the sum of their annual dose equivalent to the total body or to any organ shall not exceed 4 millirem/year.

Exact / Rounded

Exact

Scope

State

Policy point of origin

U.S. National Primary Drinking Water Regulations

Legal standard / Guideline

Standard

Year of adoption

2002 (updated 2007)

Technical / legal reference(s)

California Regulations Related to Drinking Water, CCR Title 22, Div. 4, Chap 15, Article 5

Enforcement

 

Consequences of exceeding limit

 

Target population:

 

All ages and sexes
No : Adult
Urban
Yes
Rural
Yes
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
 
Committed effective dose
4 mrem/year (0.04 mSv/year)

Comment

 

Safety factor

 

Context :

 

CANDU reactors
0
Total power reactors
4

Research centres

Tritium light manufacturing

 

General comments

The current California maximum contaminant level (MCL) for tritium in drinking water is 20,000 pCi/L (740 Bq/L).

The Office of Environmental Health Hazard Assessment 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. PHGs established by OEHHA are not regulatory in nature 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, if one exists. PHGs are based solely on scientific and public health considerations, without regard to economic cost considerations or technical feasibility. The ongoing revision of the California drinking water standards (MCLs) will consider the PHG for tritium in drinking water along with pertinent economic factors and technical feasibility.

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* Level currently under revision

Jurisdiction

Canada

Tritium limit in drinking water

7,000 Bq/L *

Committed effective dose

0.1 mSv/year

Additional considerations

The sum of the committed effective doses from all radionuclides is not to exceed 0.1 mSv/year.

Exact / Rounded

Roudned down to the next 1,000

Scope

National

Policy point of origin

ICRP

Legal standard / Guideline

Guideline

Year of adoption

1995

Technical / legal reference(s)

Enforcement

None (guideline only, except in Ontario)

Consequences of exceeding limit

None

Target population :

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes
Applicability
 
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

MAC (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11Sv/Bq)


Calculation = 7,610 Bq/L, rounded down to 7,000

Safety factor

A recommended reference dose level (RDL) of the committed effective dose, equal to 0.1 mSv from 1 year’s consumption of drinking water (from the possible total radioactive contamination of the annual drinking water consumption). This comprises 10% of the intervention exemption level recommended by the ICRP for dominant commodities (e.g., food and drinking-water) for prolonged exposure situations, which is most relevant to long-term consumption of drinking water by the public (ICRP, 2000). The RDL of 0.1 mSv is also equal to 10% of the dose limit for members of the population, recommended by both the ICRP (1991) and the International Basic Safety Standards (IAEA, 1996).

Context:

 

CANDU reactors
17
Total power reactors
17
Research centres
1
Tritium light manufacturing
Tritium removal facility
1

General comments

When two or more radionuclides are found in drinking water, the following relationship should be satisfied:

  C1/MAC1  +  C2/MAC2  + …Ci/MACi    ≤1

where Ci and MACi are the observed and maximum acceptable concentrations, respectively, for each contributing radionuclide.

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* Level currently under revision

* 1 operating facility in September 2007

Jurisdiction

China

Tritium limit in drinking water

No specific guideline or standard.
WHO guidelines used in environmental samples.

Committed effective dose

 

Additional considerations

 

Exact / Rounded

 

Scope

 

Policy point of origin

 

Legal standard / Guideline

Standards for drinking water quality (GB 5749-2006). Limited concentrations of radionuclides in foods (GB 14482-94)

Standards do not include radioactivity.

Year of adoption

 

Technical / legal reference(s)

Personal communication with the National Institute for Radiological Protection (September 30, 2007)

Enforcement

 

Consequences of exceeding limit

 

Target population:

All ages and sexes

Urban

Rural

 

Applicability

 

Technical basis for calculation:
 
Drinking water intake rate
 
Dose conversion factor
 
Committed effective dose
 

Comment

 

Safety factor

 

Context:

 

Candu reactors
2
Total power reactors
10

Research centres

Tritium light manufacturing

 

General comments

 

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Jurisdiction

European Union (EU)

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

International

Policy point of origin

WHO 2004

Legal standard / Guideline

Standard guideline

Year of adoption

1998

Technical / legal reference(s)

Enforcement

Each Member State must transpose Directive 98/83/EC into national law.

Each Member State is responsible for enforcement of its national water laws or guidelines.

Monitoring for tritium is not required if justifiable.

Consequences of exceeding limit

None at EU level unless risk to public health in several EU Member States.

Target population:

 

 

All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes

Applicability

‘Water intended for human consumption’ shall mean :

(a) all water either in its original state or after treatment, intended for drinking, cooking, food preparation or other domestic purposes, regardless of its origin and whether it is supplied from a distribution network, from a tanker, or in bottles or containers;

(b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form;

Exclusion:

(a) natural mineral waters recognised as such by the competent national authorities, in accordance with Council Directive 80/777/EEC of 15 July 1980 on the approximation of the laws of the Member States relating to the exploitation and marketing of natural mineral waters (1);

(b) waters which are medicinal products within the meaning of Council Directive 65/65/EEC of 26 January 1965 on the approximation of provisions laid down by law, regulation or administrative action relating to medicinal products (2).

Possible exclusion (each member State must decide whether to exclude or not):

“Water intended for human consumption from an individual supply providing less than 10 m³ a day as an average or serving fewer than 50 persons, unless the water is supplied as part of a commercial or public activity.”

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC. [see also ISTISAN, 2000]

Safety factor

Maximum dose (0.1 mSv/y) is 10 percent of the dose limit for members of the population (see WHO form for details)

Context :

 
CANDU reactors
2
Total power reactors
133

Research centres

Tritium light manufacturing

 

General comments

See WHO/EU for detailed comments.

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Jurisdiction

Finland

Tritium limit in drinking water

30,000 Bq/L

Committed effective dose

0.5 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.5 mSv/year

Exact / Rounded

Rounded to the nearest 1,000

Scope

National

Policy point of origin

National

Legal standard / Guideline

Standard

Year of adoption

1993

Technical / legal reference(s)

Radioactivity of Household Water (ST 12.3), STUK

Enforcement

 

Consequences of exceeding limit

 

Target population:

 

All ages and sexes
No: Adult dose conversion factor
Urban
 
Rural
 

Applicability

Household water comprises water used for drinking, water used in the production of beverages, and water used in preparing or producing foods industrially.

Technical basis for calculation:
 
Drinking water intake rate
2.2 L/day (803 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.5 mSv/year

Comment

Level (Bq/L) = 5 × 10 -4 (Sv/year) /
803 (L/year) × DCF (1.8 x 10 -11Sv/Bq)

Calculation = 34,592 Bq/L, rounded down to 30,000

Safety factor

 

Context:

 

CANDU reactors
0
Total power reactors
4
Research centres
0
Tritium light manufacturing
0

General comments

Although Finland is a member of the EU, it has not yet implemented Council Directive 98/83/EC

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Jurisdiction

France

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

National

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

Standard

Year of adoption

2001

Technical / legal reference(s)

Decree No. 2001-1220 relative to water intended for human consumption, excluding mineral water
http://www.car-analyse.com/hydro/d011220.htm

Enforcement

Transposition of EU Directive 98/83/EC into national law

Consequences of exceeding limit

Test for presence of other artificial radionuclides

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes
Applicability

Decree applies to:

(a) all water either in its original state or after treatment, intended for drinking, cooking, food preparation or other domestic purposes, regardless of its origin and whether it is supplied from a distribution network, from a tanker, or in bottles or containers;

(b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form, including water-based food ice.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)


Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 
CANDU reactors
0
Total power reactors
59
Research centres
ITER fusion project
Tritium light manufacturing
0

General comments

See WHO comments.

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Jurisdiction

Germany

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

National

Policy point of origin

ER Directive 98/83/EC

Legal standard / Guideline

Standard

Year of adoption

2001

Technical / legal reference(s)

Drinking Water Regulation (TrinkwV-2001) [in German]
http://bundesrecht.juris.de/
trinkwv_2001/index.html

Enforcement

Transposition of EU Directive 98/83/EC into national law

Consequences of exceeding limit

Fines and penalties if contamination is high or low and not quickly remediated.

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes/div>

Applicability

Applies to:

(a) all water either in its original state or after treatment, intended for drinking, cooking, food preparation or other domestic purposes, including the cleaning of items that may come into contact with foodstuffs or the human body.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)


Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 

 
CANDU reactors
0
Total power reactors
17
Research centres
7
Tritium light manufacturing
0

General comments

See WHO comments.

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Jurisdiction

Italy

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Scope

Policy point of origin

Legal standard / Guideline

Standard guideline

Year of adoption

2001

Technical / legal reference(s)

Legislative Decree, 2 February 2001, no. 31 “Application of Directive 98/83/EC Relative to the Quality of Water Destined for Human Consumption." [in Italian] http://www.parlamento.it/leggi/
deleghe/01031dl.htm

Enforcement

Transposition of Directive 98/83/EC into national law

Consequences of exceeding limit

    

Target population:

 

All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes
Applicability

As defined in the EU Directive 98/83/EC:

‘water intended for human consumption’ shall mean :

(a) all water either in its original state or after

treatment, intended for drinking, cooking, food

preparation or other domestic purposes, regardless

of its origin and whether it is supplied from a distribution network, from a tanker, or in bottles

or containers;

(b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form;

Exclusion :

(a) natural and medicinal mineral waters

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)


Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 

CANDU reactors
0
Total power reactors
0
Research centres
0
Tritium light manufacturing
0

General comments

See WHO comments.

Top of page

Jurisdiction

Japan

Tritium limit in drinking water

No guideline or standard

Committed effective dose

 

Additional considerations

 

Exact / Rounded

 

Scope

 

Policy point of origin

 

Legal standard / Guideline

Water quality standards do not include radioactivity.
http://www.jwwa.or.jp/english/water_en/water-e07.html

Year of adoption

 

Technical / legal reference(s)

Personal communication with the Office of Radiation Regulation, Science and Technology Policy Bureau; Ministry of Education, Culture, Sports, Science and Technology (July 31, 2007).

Enforcement

 

Consequences of exceeding limit

 

Target population:

All ages and sexes

Urban

Rural

 

Applicability

 

Technical basis for calculation:

Drinking water intake rate

Dose conversion factor

Committed effective dose

Comment

 

Safety factor

 

Context:

CANDU reactors
0
Total power reactors
53
Research centres
 
Tritium light manufacturing
 

General comments

 

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Jurisdiction

Manitoba

Tritium limit in drinking water

7,000 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

The sum of the committed effective doses from all radionuclides is not to exceed 0.1 mSv/year.

Exact / Rounded

Rounded down to the next 1,000

Scope

Provincial

Policy point of origin

Guidelines for Canadian Drinking Water Quality

Legal standard / Guideline

Standard

Year of adoption

2002

Technical / legal reference(s)

Drinking Water Safety Act

Drinking Water Safety Regulation

Drinking Water Quality Standards Regulation

http://www.gov.mb.ca/waterstewardship/
odw/reg-info/acts-regs/index.html

Enforcement

Manitoba Office of Drinking Water, as per the Act, regulation and standards mentioned above

Consequences of exceeding limit

 

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes

Applicability

 
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

MAC (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L, rounded down to 7,000

Safety factor

A recommended reference dose level (RDL) of the committed effective dose, equal to 0.1 mSv from 1 year’s consumption of drinking water (from the possible total radioactive contamination of the annual drinking water consumption). This comprises 10 percent of the intervention exemption level recommended by the ICRP for dominant commodities (e.g., food and drinking-water) for prolonged exposure situations, which is most relevant to long-term consumption of drinking water by the public (ICRP, 2000). The RDL of 0.1 mSv is also equal to 10 percent of the dose limit for members of the population, recommended by both the ICRP (1991) and the International Basic Safety Standards (IAEA, 1996).

Context:

 

CANDU reactors
0
Total power reactors
0
Research centres
0
Tritium light manufacturing
0

General comments

When two or more radionuclides are found in drinking water, the following relationship should be satisfied:

  C1/MAC1  +  C2/MAC2  + …Ci/MACi    ≤1

where Ci and MACi are the observed and maximum acceptable concentrations, respectively, for each contributing radionuclide.

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Jurisdiction

New Brunswick

Tritium limit in drinking water

None

Committed effective dose

 

Additional considerations

 

Exact / Rounded

 

Scope

Policy point of origin

Legal standard / Guideline

Guideline

Year of adoption

1993

Technical / legal reference(s)

Enforcement

 

Consequences of exceeding limit

 

Target population:

All ages and sexes

Urban

Rural

   

Applicability

 

Technical basis for calculation:

Drinking water intake rate

Dose conversion factor

Committed effective dose

Comment

   

Safety factor

 

Context:

 

CANDU reactors
1
Total power reactors
1
Research centres
0
Tritium light manufacturing
0

General comments

 

Top of page

Jurisdiction

Northern Ireland

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

Regional

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

Standard

Year of adoption

2001

Technical / legal reference(s)

Statutory Rule 2007 No. 147

“The Water Supply (Water Quality) Regulations (Northern Ireland) 2007”
http://www.opsi.gov.uk/sr/
sr2007/20070147.htm#sch2

Enforcement

 

Consequences of exceeding limit

 

Target population :

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes

Applicability

Applies to water supplied:

(a) for such domestic purposes as consist in or include, cooking, drinking, food preparation or washing; or

(b) to premises in which food is produced, wholesomeness of the foodstuff in its finished form.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10 percent of the dose limit for members of the population (see WHO form for details).

Context:

 
CANDU reactors
0
Total power reactors
0
Research centres
0
Tritium light manufacturing
0

General comments

See WHO comments.

Top of page

Jurisdiction

Norway

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

National

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

Standard

Year of adoption

2001

Technical / legal reference(s)

Drinking Water Regulations
FOR 2001-12-04 nr 1372 [In Norwegian]
http://www.lovdata.no/cgi-wift/ldles?doc=/sf/sf/sf-20011204-1372.html

Enforcement

Transposition of EU Directive 98/83/EC into national law

Consequences of exceeding limit

As per Food Law (LOV 2003-12-19-124); investigation required

Target population:

 

All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes
Applicability

“drinking water” definition :

(a) all water either in its original state or after treatment, intended for drinking, cooking, food preparation or other domestic purposes, regardless of its origin and whether it is supplied from a distribution network, from a tanker, or in bottles or containers;

(b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 

CANDU reactors
0
Total power reactors
0
Research centres
1 (Halden Reactor Project)
Tritium light manufacturing
0

General comments

See WHO comments.

Top of page

Jurisdiction

Ontario

Tritium limit in drinking water

7,000 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

The sum of the committed effective doses from all radionuclides is not to exceed 0.1 mSv/year.

Exact / Rounded

Rounded down to the next 1,000

Scope

Provincial

Policy point of origin

Guidelines for Canadian Drinking Water Quality

Legal standard / Guideline

Standard

Year of adoption

2002

Technical / legal reference(s)

Ontario Safe Drinking Water Act, 2002

Ontario Drinking water Quality Standards
(O. Reg. 169/03 and 242/07)
http://www.canlii.org/on/
laws/regu/2003r.169/20070717/whole.html

Ontario Drinking Water Systems Regulation
(O. Reg. 170/03)
http://www.canlii.org/on/laws/
regu/2003r.170/20070717/whole.html

Enforcement

Ontario Ministry of the Environment, as per the regulation and standards mentioned above

Consequences of exceeding limit

 

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes

Applicability

 
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

MAC (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L, rounded down to 7,000

Safety factor

A recommended reference dose level (RDL) of the committed effective dose, equal to 0.1 mSv from 1 year’s consumption of drinking water (from the possible total radioactive contamination of the annual drinking water consumption). This comprises 10 percent of the intervention exemption level recommended by the ICRP for dominant commodities (e.g., food and drinking-water) for prolonged exposure situations, which is most relevant to long-term consumption of drinking water by the public (ICRP, 2000). The RDL of 0.1 mSv is also equal to 10 percent of the dose limit for members of the population, recommended by both the ICRP (1991) and the International Basic Safety Standards (IAEA, 1996).

Context :

 
CANDU reactors
16
Total power reactors
0
Research centres
4
Tritium light manufacturing
Tritium removal facility
1

General comments

When two or more radionuclides are found in drinking water, the following relationship should be satisfied:

  C1/MAC1  +  C2/MAC2  + …Ci/MACi    ≤1

where Ci and MACi are the observed and maximum acceptable concentrations, respectively, for each contributing radionuclide.

Top of page

* 1 operating facility in September 2007


Jurisdiction

Quebec

Tritium limit in drinking water

7,000 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

The sum of the committed effective doses from all radionuclides is not to exceed 0.1 mSv/year.

Exact / Rounded

Rounded down to the next 1,000

Scope

Provincial

Policy point of origin

Guidelines for Canadian Drinking Water Quality

Legal standard / Guideline

Standard

Year of adoption

2003

Technical / legal reference(s)

Enforcement

The Ministère du Développement durable, de l’Environnement et des Parcs is responsible for enforcement, as per the regulation mentioned above.

Consequences of exceeding limit

 

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes

Applicability

 
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

MAC (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L, rounded down to 7,000

Safety factor

A recommended reference dose level (RDL) of the committed effective dose, equal to 0.1 mSv from 1 year’s consumption of drinking water (from the possible total radioactive contamination of the annual drinking water consumption). This comprises 10 percent of the intervention exemption level recommended by the ICRP for dominant commodities (e.g., food and drinking-water) for prolonged exposure situations, which is most relevant to long-term consumption of drinking water by the public (ICRP, 2000). The RDL of 0.1 mSv is also equal to 10 percent of the dose limit for members of the population, recommended by both the ICRP (1991) and the International Basic Safety Standards (IAEA, 1996).

Context:

 
CANDU reactors
1
Total power reactors
0
Research centres
0
Tritium light manufacturing
0

General comments

When two or more radionuclides are found in drinking water, the following relationship should be satisfied:

  C1/MAC1  +  C2/MAC2  + …Ci/MACi    ≤1

where Ci and MACi are the observed and maximum acceptable concentrations, respectively, for each contributing radionuclide.

Top of page

Jurisdiction

Republic of Korea

Tritium limit in drinking water

No guideline or standard

Committed effective dose

 

Additional considerations

 

Exact / Rounded

 

Scope

 

Policy point of origin

 

Legal standard / Guideline

 

Year of adoption

 

Technical / legal reference(s)

Personal communication with the Korea Institute of Nuclear Safety (KINS) (26 July, 2007)

Enforcement

 

Consequences of exceeding limit

 

Target population:

All ages and sexes

Urban

Rural

 

Applicability

 

Technical basis for calculation:

Drinking water intake rate

Dose conversion factor

Committed effective dose

Comment

 

Safety factor

 

Context:

 
CANDU reactors
4
Total power reactors
20
Research centres
 
Tritium light manufacturing
 

General comments

 

Top of page

Jurisdiction

Romania

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

National

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

standard

Year of adoption

2002

Technical / legal reference(s)

Water Law No. 458/2002 “Concerning the Quality of Potable Water" [in Romanian]

Enforcement

Transposition of EU Directive 98/83/EC into national law.

Amendment 311/2004 (to law 458/2002). The Ministry of Health supervises and controls the monitoring of water quality.

Consequences of exceeding limit

 

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes

Applicability

As defined in the EU Directive 98/83/EC:

‘water intended for human consumption’ shall mean :

(a) all water either in its original state or after
treatment, intended for drinking, cooking, food
preparation or other domestic purposes, regardless of its origin and whether it is supplied from a distribution network, from a tanker, or in bottles or containers;

(b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form;

Exclusion :

(a) natural mineral waters recognised as such by the competent national authorities, in accordance with Council Directive 80/777/EEC of 15 July 1980 on the approximation of the laws of the Member States relating to the exploitation and marketing of natural
mineral waters (1);

(b) waters which are medicinal products within the meaning of Council Directive 65/65/EEC of 26 January 1965 on the approximation of provisions laid down by law, regulation or administrative action relating to medicinal products (2).

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 
CANDU reactors
2
Total power reactors
2
Research centres
1
Tritium light manufacturing
0

General comments

See WHO comments.

Top of page

Jurisdiction

Russia

Tritium limit in drinking water

7,700 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

 

Exact / Rounded

Rounded to the nearest 100

Scope

National

Policy point of origin

Assumed

Legal standard / Guideline

Standard

Year of adoption

1999

Technical / legal reference(s)

Radiation Safety Norms (NRB-99)

Enforcement

 

Consequences of exceeding limit

 

Target population:

 
All ages and sexes
No : Value identified for "critical receptor" of child 1-2 years
Urban
 
Rural
 

Applicability

 
Technical basis for calculation:
 
Drinking water intake rate
730 L/year
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L, rounded to 7,700 Bq/L

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population.

Context:

 
CANDU reactors
0
Total power reactors
31
Research centres
 
Tritium light manufacturing
0

General comments

See WHO comments.

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Jurisdiction

Scotland

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

Regional

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

Standard

Year of adoption

2001

Technical / legal reference(s)

2001 No. 207 The Water Supply (Water Quality) ( Scotland) Regulations 2001
http://www.opsi.gov.uk/legislation/
scotland/ssi2001/ssi_20010207_en.pdf

Enforcement

 

Consequences of exceeding limit

 

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
 
Rural
 

Applicability

Applies to water supplied:

(a) for such domestic purposes as consist in or include, cooking, drinking, food preparation or washing; or

(b) for any of those domestic purposes to premises in which food is produced.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 
CANDU reactors
0
Total power reactors
2
Research centres
0
Tritium light manufacturing
0

General comments

See WHO comments.

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Jurisdiction

Spain

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

National

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

Standard

Year of adoption

2003

Technical / legal reference(s)

"Royal Decree 140/2003, by Which are Established the Sanitary Criteria of the Quality of Water for Human Consumption." [in Spanish]
http://www.msc.es/ciudadanos/
saludAmbLaboral/docs/rd_140_2003.pdf

Enforcement

Transposition of EU Directive 98/83/EC into national law.

Non-conforming water quality results reported to the Sistema de Información Nacional de Agua de Consumo.

Consequences of exceeding limit

Depending on severity, possible stop to activities and water distribution and/or public warning. Sanctions (according to law 14/1986) if corrective measures not implemented quickly and completely.

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes

Applicability

Applies to:

(a) all water either in its original state or after treatment, intended for drinking, cooking, food preparation or other domestic purposes, regardless of its origin and whether it is supplied from a distribution network, from a tanker, or in bottles or containers;

(b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form;

Exclusions:

(a) natural mineral waters recognised as such by the competent national authorities, in accordance with Council Directive 80/777/EEC of 15 July 1980 on the approximation of the laws of the Member States relating to the exploitation and marketing of natural mineral waters (1);

(b) waters and mineral waters which are medicinal products within the meaning of laws 22/1976, 743/1928, and 25/1990.

(c) water intended for human consumption from an individual supply providing less than 10 m³ a day as an average, or serving fewer than 50 persons, unless the water is supplied as part of a commercial or public activity.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 
CANDU reactors
0
Total power reactors
8
Research centres
1
Tritium light manufacturing
0

General comments

See WHO comments.

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Jurisdiction

Sweden

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

National

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

Standard

Year of adoption

2001

Technical / legal reference(s)

“The National Food Administration's Drinking Water Regulations ( SLVFS 2001:30)” [in Swedish]

Enforcement

Transposition of EU Directive 98/83/EC into national law

Consequences of exceeding limit

As per Food Act (SFS 2006:804)

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes
Applicability

As defined in the EU Directive 98/83/EC:

‘water intended for human consumption’ shall mean :

(a) all water either in its original state or after treatment, intended for drinking, cooking, food preparation or other domestic purposes, regardless of its origin and whether it is supplied from a distribution network, from a tanker, or in bottles or containers;

(b) all water used in any food-production undertaking for the manufacture, processing, preservation or marketing of products or substances intended for human consumption unless the competent national authorities are satisfied that the quality of the water cannot affect the wholesomeness of the foodstuff in its finished form.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10 percent of the dose limit for members of the population (see WHO form for details).

Context :

 
CANDU reactors
0
Total power reactors
10
Research centres
1
Tritium light manufacturing
0

General comments

See WHO comments.

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Jurisdiction

Switzerland

Tritium limit in drinking water

10,000 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

 

Exact / Rounded

Rounded up to the next 1000

Scope

National

Policy point of origin

National

Legal standard / Guideline

Standard

Year of adoption

2006 (1995 originally)

Technical / legal reference(s)

Ordonnance du DFI sur les substances étrangères et les composants dans les denrées alimentaires (817.021.23)
http://www.admin.ch/ch/f/rs/8/
817.021.23.fr.pdf

Enforcement

 

Consequences of exceeding limit

Tolerance value set at 1,000 Bq/L. Above tolerance value, water is designated to be "of lesser value".

Above limit of 10,000 Bq/L, water is declared unfit for human consumption.

Target population:

 
All ages and sexes
 
Urban
Yes
Rural
Yes

Applicability

”Drinking water" means water, either in its original state or after treatment, intended for drinking, cooking, food preparation or for cleaning of objects coming into contact with foodstuffs.

Technical basis for calculation:
 
Drinking water intake rate
600 L/year
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 9,259.3 Bq/L, rounded up to 10,000

Safety factor
Maximum dose (0.1 mSv/y) is 10 percent of the dose limit for members of the population (see WHO form for details).

Context :

 
CANDU reactors
0
Total power reactors
5
Research centres
1
Tritium light manufacturing
1

General comments

See WHO comments.

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Jurisdiction

United Kingdom (England and Wales)

Tritium limit in drinking water

100 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

Exact

Scope

National

Policy point of origin

EU Directive 98/83/EC

Legal standard / Guideline

Standard

Year of adoption

2000; 2001

Technical / legal reference(s)

2000 No. 3184 Water, England and Wales
The Water Supply (Water Quality) Regulations 2000

Enforcement

Drinking Water Inspectorate

Consequences of exceeding limit

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.

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
 
Rural
 

Applicability

Applies to water supplied:

(a) for such domestic purposes as consist in or include, cooking, drinking, food preparation or washing; or

(b) for any of those domestic purposes, to premises in which food is produced.

Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L. Adoption of 100 Bq/L indicator parameter according to Council Directive 98/83/EC.

Safety factor

Maximum dose (0.1 mSv/y) is 10% of the dose limit for members of the population (see WHO form for details).

Context:

 
CANDU reactors
0
Total power reactors
19
Research centres
1
Tritium light manufacturing
0

General comments

See WHO comments.

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Jurisdiction

United States

Tritium limit in drinking water

740 Bq/L * (20,000 pCi/L)

Committed effective dose

4 mrem/year (0.04 mSv/year)

Additional considerations

If two or more radionuclides are present, the sum of their annual dose equivalent to the total body or to any organ shall not exceed 4 millirem/year.

Exact / Rounded

Exact

Scope

National

Policy point of origin

National

Legal standard / Guideline

Standard

Year of adoption

1976 (retained in 2003, although updated calculations would have resulted in a new standard of 2,253 Bq/L))

Technical / legal reference(s)

Enforcement

USEPA Civil Enforcement program

Consequences of exceeding limit

EPA may issue administrative orders, take legal actions, or fine utilities for violation of the standards. Under Section 1414(b) of the SDWA, an imposed penalty not to exceed $25,000 per day; under Section 1414(g)(3) of the SDWA, an administrative order can result in a $5,000 maximum penalty assessed; up to $25,000 per violation per day; under Section 1431(b), the statutory maximum is $5,000 per violation per day of an emergency order; under Section 1432(c), tampering with a public water system carries a maximum civil penalty of $50,000; a maximum civil penalty of $20,000 can be imposed for an attempt or threat to tamper with a public water system; and under Section 1445(c), the statutory maximum penalty is $25,000 in a civil judical action for failing or refusing to keep appropriate records, make reports, etc.

Target population:

 
All ages and sexes
No : Adult
Urban
Yes
Rural
Yes

Applicability

 
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
4 mrem/year (0.04 mSv/year)

Comment

 

Safety factor

 

Context :

 
CANDU reactors
0
Total power reactors
103
Research centres
 
Tritium light manufacturing
 

General comments

Except for the radionuclides listed in Table A, the concentration of man-made radionuclides causing 4 mrem total body or organ dose equivalents shall be calculated on the basis of a 2 liter per day drinking water intake using the 168 hour data listed in "Maximum Permissible Body Burdens and Maximum Permissible Concentration of Radionuclides in Air or Water for Occupational Exposure,'' NBS Handbook 69 as amended August 1963, U.S. Department of Commerce.

Table A--Average Annual Concentrations
Assumed to Produce a Total Body
or Organ Dose of 4 mrem/yr

----------------------------------------
Radionuclide..........Critical organ...........pCi per liter

---------------------------------------
Tritium.................. Total body.............. 20,000

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Level currently under revision

Jurisdiction

World Health Organisation (WHO)

Tritium limit in drinking water

10,000 Bq/L

Committed effective dose

0.1 mSv/year

Additional considerations

Total indicative dose from radionuclides not to exceed 0.1 mSv/year

Exact / Rounded

(Rounded by averaging the log scale values)

Scope

Policy point of origin

n/a

Legal standard / Guideline

Guideline

Year of adoption

2004

Technical / legal reference(s)

Guidelines for Drinking water Quality. Vol. 1 : 3rd ed.
http://www.who.int/water_sanitation_health/dwq/
GDWQ2004web.pdf

Enforcement

n/a

Consequences of exceeding limit

n/a

Target population:

 
All ages and sexes
No: Adult dose conversion factor
Urban
Yes
Rural
Yes

Applicability

 
Technical basis for calculation:
 
Drinking water intake rate
2 L/day (730 L/year)
Dose conversion factor
1.8 x 10 -11 Sv/Bq
Committed effective dose
0.1 mSv/year

Comment

Level (Bq/L) = 1 × 10 -4 (Sv/year) /
730 (L/year) × DCF (1.8 x 10 -11 Sv/Bq)

Calculation = 7,610 Bq/L, rounded up to 10,000

Safety factor

A recommended reference dose level (RDL) of the committed effective dose, equal to 0.1 mSv from 1 year’s consumption of drinking water (from the possible total radioactive contamination of the annual drinking water consumption). This comprises 10 percent of the intervention exemption level recommended by the ICRP for dominant commodities (e.g., food and drinking-water) for prolonged exposure situations, which is most relevant to long-term consumption of drinking water by the public (ICRP, 2000). The RDL of 0.1 mSv is also equal to 10 percent of the dose limit for members of the population, recommended by both the ICRP (1991) and the International Basic Safety Standards (IAEA, 1996).

Context:

 
CANDU reactors
n/a
Total power reactors
n/a
Research centres
n/a
Tritium light manufacturing
n/a

General comments

The dose coefficient for adults was provided by the ICRP.

The nominal probability coefficient for radiation-induced stochastic health effects, which include fatal cancer, non-fatal cancer and severe hereditary effects for the whole population, is 7.3 x 10-2/Sv (ICRP, 1991). Multiplying this by an RDL equal to 0.1 mSv annual exposure via drinking water gives an estimated lifetime risk of stochastic health effects of 10-5, which can be considered small in comparison with other health risks. This risk level is comparable to the reference level of risk used elsewhere in these Guidelines.

Background radiation exposures vary widely across various regions of the Earth, but the average is about 2.4 mSv/year, with the highest local levels being up to 10 times higher without any apparent health consequences; 0.1 mSv therefore represents a small addition to background levels.

Despite the uncertainties in the determination of risk from radiation exposure at low levels, radiation risks are probably well below those due to microbes and some chemicals in drinking-water.