IICPH appreciates the importance of the Tritium Studies Project. Tritium is of particular importance in Canada, as CANDU reactors produce and release significantly more tritium than other types of reactors.
Ms Louise Levert
Secretariat, Canadian Nuclear Safety Commission
280 Slater Street, P.O. Box 1046
Ottawa, Ontario K1P 5S9
Re: Comments on Tritium Studies Project
IICPH appreciates the importance of the Tritium Studies Project. Tritium is of particular importance in Canada, as CANDU reactors produce and release significantly more tritium than other types of reactors. In addition, large amounts of tritium are released from research facilities (Chalk River Laboratories in particular) and from industries that use tritium to produce gaseous light sources (SRB Technologies and Shield Source Incorporated).
At the same time, IICPH is concerned about the very limited time accorded for public response to the studies produced in this project. Given this time restraint, IICPH has chosen to focus its comments on the following topics with reference to the CNSC documents as noted:
- Derived Release Limits (DRLs) – Tritium Releases and Dose Consequences in Canada in 2006, INFO-0793, December 2009
- Darlington’s Tritium Recovery Facility – Evaluation of Facilities Handling Tritium INFO-0796, February 2010
- Health Effects, Dosimetry (ICRP) – Health Effects, Dosimetry and Radiological Protection of Tritium INFO -0799, April 2010
- Tritium Drinking Water Guidelines/Standards – Standards and Guidelines for Tritium in Drinking Water INFO-0766, January 2008
These topics are interrelated, in that the present permissible dose levels are an underlying factor that is used to set release limits and water guidelines for tritium. The International Commission on Radiation Protection (ICRP) Dosimetry, upon which Canada is reliant, has been challenged by the European Committee on Radiation Risk and several members of the science and health community, including IICPH.
As this submission will point out, IICPH remains concerned over the present permissible safe dose of radiation and assumptions that have been made in its derivation.
Firstly and foremost, there is no safe level of exposure to ionizing radiation. This has been clearly acknowledged in the most publication of the National Academy of Science series “Biological Effects of Ionizing Radiation” BEIR VII Report. Therefore, the maximum safe dose of any ionizing radiation is zero. Any other value set for a safe dose is based on the degree of risk, that is, the degree of harm to human health and the environment that is tolerated by regulatory bodies. Thus, it follows that any prescribed limits based on the current ICRP safe dose are fundamentally unsound.
A. Derived Release Limits (DRL’s)
“Derived Release Limits” (DRLs) are the legal upper bounds for releases to the environment regulated by the CNSC. DRLs are models that translate ICRP “public doses” into site-specific levels. In addition to the use of the ICRP safe dose, the DRLs are highly flawed as regulatory tools. For example;
- Dose estimates for air emissions are based upon assumptions of the behaviour of stack plumes which are extremely difficult to model.
- Estimates of public doses arising from waterborne discharges of radionuclides are based on the dilution capacity of receiving waters and are based on average, rather than minimum flow, which would be more appropriate, given the effect of climate change on minimum flows.)
- The methods for calculating DRLs do not account for doses that occur over a number of years, and ignore the accumulation of radionuclides in the environment and in individuals.
- DRL models are prepared by the licensee. Licensees may choose model parameters that underestimate doses and allow much higher emissions than if doses were conservatively estimated.
- The DRL-setting process is closed to the public and does not involve peer review by independent scientific experts.
Furthermore, in reporting tritium emissions, nuclear licensees and the CNSC routinely express these emissions also as “percentages of DRLs”, rather than showing the actual DRLs. This gives the public the impression that because emissions are well below the regulated limit, the emissions themselves are not a problem.
Tritium Releases from Nuclear Generating Stations (2006)
The following table is an extract of Table 2 (INFO -0793) for tritium releases and the associated DRL for three nuclear stations for the year 20061;
|Facility||Gaseous Emissions Bq/year||Liquid Effluents Bq/year|
|Tritium oxide (HTO)||% DRL||Tritium oxide (HTO)||% DRL|
|Darlington, On||1.3 x 1014||0.3||1.9 x 1014||0.004|
|Bruce, On||9.0 x 1014||1.0||7.3 x 1014||0.226|
|Point Lepreau, NB||9.0 x 1014||0.04||1.6 x 1014||0.001|
Note: The release limits themselves are not given.
Similarly, for the company SRB Technologies, releases of HTO for 2006 were 7.2 × 1013 Bq, (4.8% of the “release limit”).2
Clearly, DRLs are extremely lax, in some cases orders of magnitude higher than actual discharges. As such, they do not “restrict” the amounts actually discharged. Rather, DRLs are designed to give the licensee free reign to emit tritium.
IICPH recommends that the whole methodology for setting release limits must be reviewed and subject to public scrutiny. The regulator must be responsible for establishing limits that are protective of public health and the environment, and not of the industry.
B. Darlington Treatment Removal Facility (TRF)
The Darlington Treatment Removal Facility (TRF), operated by Ontario Power Generation (OPG), was established in 1990 to limit worker exposure to excessive levels of tritium. Not only does it store vast amounts of tritium in gaseous from, it also emits tritium gas. There was no mention of releases of tritium from the TRF in the CNSC publication on “Tritium Releases and Dose Consequences in Canada in 2006”, or release limits. The TRF was discussed briefly in CNSC’s “Evaluation of Facilities Handling Tritium”, p. 9, where it indicated that TRF released 95 TBq of HT in 2006.
In another source (Ian Fairlie 2007), HT releases for 2005 were 790 TBq.
This facility is of particular interest and concern, as related to SRB Technologies which receives some of the tritium from TRF for its processing, and as a result of this, large amounts of tritium have been released in the Ottawa valley.
IICPH is requesting the following information on TRF:
- Its storage capacity;
- The amounts of tritium released from TRF (monthly, yearly) and its permitted release limit; and
- A mass balance analysis for tritium at TRF; that is how much is shipped to TRF, sent elsewhere, and emitted, on an annual or monthly basis.
C. Health Effects
Both gaseous and aqueous forms of tritium (HT and HTO respectively) are very radioactive and pervasive.3 HT permeates most materials, rubber and many grades of steel with relative ease, and HTO, which is chemically identical and physically similar to ordinary water, very rapidly mixes everywhere.
Tritium is a carcinogen, mutagen, teratogen and developmental toxin which is easily absorbed into the body. Tritium exchanges easily with H atoms, and binds with organic compounds to form Organic Bound Tritium (OBT). It becomes incorporated into DNA. It disrupts the genetic code of women’s reproductive cells. The cells most at risk from tritium would be those dividing at the time of exposure (precursor cells for the ovum), the embryo and nerve cells.
Tritium easily crosses the placenta, which raises concern for spontaneous abortions, stillbirths, congenital malformations and diseases.
Since tritium spontaneously disintegrates into a helium atom, the resulting recoil excitation can disrupt chemical bonds. These disruptions when reproduced cause chronic diseases such as allergies or hormonal dysfunction.
D. Environmental Pathways
Tritium is absorbed through inhalation, ingestion and dermal absorption. The following figure, from CNSC’s document on “Tritium Doses and Consequences in Canada”, demonstrates the numerous exposure pathways:4
Sources of Exposure:
- Plume: Inhalation of HT and HTO
- Soil: Inhalation and dermal absorption of HTO
- Food: Inhalation of HTO and OBT
- Location relative to plume
- Duration in the plume area
- Breathing zone height above ground surface
- Inhalation rate
- Amount and type of food grown in initial plume area that is consumed
- Age, sex, etc.
A number of studies in Canada have demonstrated the health detriments of tritium, including an increase in the number of fatal birth defects and neonatal deaths in the area of the Pickering nuclear facility, an increase in Down’s syndrome and central nervous system anomalies in births in the Pickering area, and an increase in child leukemia deaths near the Bruce plant. As well, the IARC (International Agency for Research on Cancer) study of Nuclear Workers found that radiation related cancer rates of Canadian nuclear workers are higher than that of other nuclear workers receiving the same radiation dose.5
Despite these studies and others in other countries (England, Germany, for example) that should alert regulators to the dangers posed by nuclear operations, denial pervades the regulator, and the industry. The burden of proof is being placed on the people to prove harm, rather than on the industry and government to prove no harm.
E. Organic Bound Tritium (OBT)
This form of tritium has been well recognized for years. However, there has been little movement in dealing with the extent to which OBT affects human health and biota. IICPH believes that the importance of OBT must be strongly emphasized as it indicates the extent to which insidious exposure to tritium is detrimental. The following text describes issues related to OBT:
Tritium rapidly enters all material containing hydrogen. Some of this absorbed tritium reacts with organic compounds and is called organically bound tritium (OBT), a very important component of tritium exposures. When there are repeated (i.e., chronic) exposures to tritium, concentrations of OBT gradually increase in all biota. Humans accumulate OBT by consuming OBT in tritium-contaminated food and by drinking/eating, breathing and absorbing tritiated water (HTO). OBT is more problematic than HTO because of its much longer residence time and because OBT by its very nature is located near organic molecules (for example, DNA).6
The OBT fraction of tritiated water has two components. The first, OBT 1, is exchangeable, that is, it easily reacts with other chemicals in the internal environment and binds with oxygen, sulfur, phosphorus or nitrogen atoms, to form amino acids, proteins, sugars, starches, lipids, and cell structural material which are then used and ‘destroyed’ within the body and excreted in time. Since OBT1 has a biological half-life of about 40 days, it will remain in the body for about that time.
Chronic exposure to tritiated water (HTO) in food will cause an increase in the exchangeable fraction of OBT (OBT1) to approximately the same proportion as HTO, as one would expect in an area such as Pembroke, exposed to extreme levels of tritium pollution for twenty years from SRB Technologies from its manufacturing of gaseous tritium light sources.
The second more fixed component, OBT 2, also referred to as non-exchangeable OBT, binds with the carbon atoms of the DNA. This OBT2 has a biological half-life of about 550 days. Since the DNA in the cell is not frequently replaced, being bound to DNA will keep the tritium inside the cells for an average of 550 days. The longer exposure time will increase the deposit of energy in a tissue by a factor of three, analogous to sitting in the sun longer and getting a worse burn.
The non-homogeneous distribution of the two OBT components in the body will mean higher localized absorbed doses, each at least four times higher than the average dose for uniform spread of HTO. This will increase the estimate of energy deposited generally by another factor of three.
F. International Commission on Radiological Protection (ICRP) – Dosimetry
The Sievert, the equivalent dose to a tissue, is a risk-based unit of measurement that estimates the probability that a given exposure will result in a fatal cancer. Basing risk on fatal cancers alone does not mean that other radiation related health effects will not occur.
The ICRP methodology and underlying assumptions for calculating the internal absorbed dose are flawed for a number of reasons.7 For example;
- ICRP considers that HTO doses from inhalation and ingestion are 25,000 times greater than for HT, because the body is not thought to absorb or metabolize hydrogen gas, whereas water is a vital component of all body tissues and metabolic processes. However, HT dispersed into the atmosphere diffuses readily into the soil and is converted to HTO in soil, the rate of which depends on certain soil conditions such as porosity, water content and microbial activity. The converted HT is subsequently transported as HTO.
- The distribution of OBT in the whole body is assumed to be homogeneous. This is not the case, as it is actually localized in certain tissues.
- Lack of consideration has been given to the greater harmfulness of OBT compared to HTO.
- ICRP has significantly underestimated the length of time that OBT1 and OBT 2 remains in the human body after long-term exposure to OBT. In its dose models for tritium, the ICRP and CNSC do not fully recognise increases in OBT concentrations from repeated exposures.
- ICRP recognizes only severe genetic effects in live-born offspring, and does not take into account cases such as miscarriage and stillbirth, teratogenic effects, such as congenital malformations or diseases, or childhood asthma.8
- Salient factors such as chronic exposure, non-cancerous effects, nor the damage done by tritium to DNA, chronic illnesses due to non-functional enzymes, hormones and essential proteins are not considered, despite evidence that these effects occur.
- ICRP applies a Relative Biological Effectiveness (RBE) Factor of 1 for tritium in determining its dose limit, whereas for most government regulations, the RBE for electron and photon radiation is 1, it is 10for neutron radiation, and 20 for alpha radiation. The issue of RBEs is controversial, from the very restricted set of values to that for tritium. Based on several factors mentioned above and a consensus of scientific research, the RBE for tritium is severely underestimated and needs to be increased by a factor of two to three.9
- The ICRP risk-based system of protection relates to “reference persons” and does not take account of age, size and sex differences in risk factors.
- It ignores the fact that there is no safe level of exposure to radiation.
- The distribution of risk of fatal cancers in the exposed population based on ICRP methodology and accepted in Canada by CNSC is biased against women and children who will bear the burden of the risks.
However, the CNSC report, “Health Effects, Dosimetry and Radiological Protection of Tritium”, draws the following conclusions10:
- Tritium beta radiation is about 1.4 times more effective in causing biological effects than x-rays and 2.2 times more effective than gamma rays. This means that the health risk of tritium is respectively 1.4 and 2.2 times higher than for these other types of radiation.
- The use of a radiation weighting factor of 1 in the current ICRP radiation protection framework has not decreased the level of protection afforded to workers or members of the public. This is because implementation of optimization has resulted in exposures to tritium that are very low and well below doses at which an increased risk of cancer has been observed.
- Current dosimetry and biokinetic models for assessing dose are acceptable for radiation protection purposes.
- Studies have shown that tritium exposures at current levels in Canada are highly unlikely to cause adverse health effects.
- Canada’s current regulatory framework has effectively controlled tritium exposures.
In other words, it accepts the status quo.
G. Tritium Drinking Water Guidelines/Standards
The current Canada Guideline and Ontario Drinking Water Quality Standard for tritium is 7,000 Bq/L and is based on the permissible ICRP limit of 1 mSv/year (lowered to 0.1 mSv in water).11
The Ontario Drinking Water Guideline for Tritium has been proposed to be revised to 20 Bq/L.12
20 Bq/L relates to heath effects from long-term, chronic exposure over a life time of exposure of 70 years and is within the range of variations for a 10-6 risk level. According to the Canadian Nuclear Association, it is achievable without significant cost to the nuclear power industry. In fact, in Table 1 of the CNSC study, levels of tritium in drinking water near nuclear stations tend to be below 20 Bq/L for the most part. None are anywhere near the current standard.13
The current Canadian Federal (and provincial) limit corresponds to a risk of 350 excess fatal cancers per million people and is based on the permissible ICRP limit of 1 mSv/year.
On the other hand, the Canadian Federal drinking water objectives for chemicals are set at levels that provide a lifetime risk of 1–10 excess fatal cancers per million people.
The primary reason for the difference is that the excess cancers predicted from radiation exposure are calculated by assuming one year’s consumption of drinking water: the lifetime risk is calculated as if that year of consumption were the only consumption. With chemicals, the assumption is that people consume the affected drinking water for their whole lifetime, commonly set at a 70-year exposure.
There is no rationale to explain the difference in treatment of non-radioactive chemicals and radioactive substances, other than the apparently favoured status of radiation in Canada.
While the study cites several jurisdictions water quality, two jurisdictions with stronger water quality standards are not noted. For example, in the US, Colorado has set a stricter standard for tritium in surface water, of 18.5 Bq/L. California has adopted a limit of 15 Bq/L. Both these limits are based on a one-in-a million lifetime risk of a fatal cancer, which is the goal of cleanup under the US Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), more commonly known as the Superfund.14
Tritium limits in drinking water (Bq/L)
|Agency||Tritium limit (Bq/L)|
|Canada Health and Welfare||7,000|
|US EPA (1999)||740|
|European Union (1998)||100|
|Recommended by ODWAQ||20|
IICPH has proposed the level of tritium in drinking water be zero – tritium releases from man-made sources in time, in that a zero Health Based Goal for tritium in water is the only acceptable goal for regulation from a public health standpoint.
In conclusion, a single atom of tritium can cause a lethal cancer and damage to DNA that may be carried to future generations. This is why there is no safe dose of tritium, or any other radionuclide. This is confirmed by the fact that human exposure, measured in Sieverts, estimated the probability that a given exposure will result in a fatal cancer. This acknowledges that human casualties are an inevitable result of releasing radionuclides into the environment and merely strives to keep these casualties at an “acceptable” or “reasonable” level.
But no level of casualties is “acceptable” or “reasonable” to a population that has not chosen to accept them without informed consent that scientific ethics require. Nor is even a single casualty “acceptable” to the unfortunate individual and family that suffers it.
The CNSC’s mandate is to protect the Canadian public from harm or illness from radioactive sources. As the largest polluter of tritium, Canada has an obligation to provide arm’s length independent research and not rely on ICRP for advice on regulatory standards. It should not continue support of the ICRP permissible public dose limit of 1.0 mSv/year that is neither protective nor precautionary.
Anna Tilman, B.Sc., M.A.
Member of the Board of Directors of IICPH
1 Reference: CNSC 2009: CNSC Tritium Releases and Dose Consequences in Canada in 2006, p. 17, 18 http://nuclearsafety.gc.ca/pubs_catalogue/uploads/CNSC_Release_and_Dose_eng_rev2.pdf
2 Ibid p. 18
3 One gram of HT contains about 360 TBq of radioactivity, while one gram of HTO contains about 55 TBq.
4 Reference: CNSC 2009: “Tritium Releases and Dose Consequences in Canada in 2006”, p.11 http://nuclearsafety.gc.ca/pubs_catalogue/uploads/CNSC_Release_and_Dose_eng_rev2.pdf
5 Dr. Rosalie Bertell: Health effects of tritium. (Health Effects of Tritium, Submitted to the CNSC, November 27, 2006)
6 Dr. Ian Fairlie, Tritium Hazard Report Pollution and radiation Risks from Canadian Nuclear Facilities, June 2007
7 Dr. Rosalie Bertell: Health effects of tritium. (Health Effects of Tritium, Submitted to the CNSC, November 27, 2006)
8 Dr. Ian Fairlie, Tritium Hazard Report Pollution and radiation Risks from Canadian Nuclear Facilities, June 2007
9 Relative Biological Effectiveness Factor (RBE): The equivalent dose to a tissue, the Sievert, is found by multiplying the absorbed dose, in gray, by a dimensionless “quality factor” Q, that is, the RBE, dependent upon radiation type, and by another dimensionless factor N, dependent on all other pertinent factors such as the part of the body irradiated, the time and volume over which the dose was spread, even the species of the subject. As per most government regulations, the RBE [Q] for electron and photon radiation is 1, for neutron radiation it is 10, and for alpha radiation it is 20.
11 CNSC Standards and Guidelines for Tritium in Drinking Water (January 2008) http://nuclearsafety.gc.ca/pubs_catalogue/uploads/info_0766_e.pdf
14 Ian Fairlie:Tritium hazard report: Pollution and Radiation Risk from Canadian Nuclear Facilities, June 2007