Déclassement des zones de gestion des résidus miniers d'uranium quirke/panel et stanrock/denison à elliot lake, en ontario

Résumé :

En février 1993, le déclassement de quatre zones de gestion des résidus miniers d'uranium près d'Elliot Lake, en Ontario, a été soumis à un examen public par une commission indépendante. Rio Algom Ltd. (responsable des zones de gestion des résidus Quirke/Panel) et Denison Mines Ltd. (responsable des zones de gestion des résidus Denison/Stanrock) ont présenté une demande de permis à la Commission de contrôle de l'énergie atomique (CCEA) afin de déclasser ces sites. Les quatres sites sont associés à des mines d'uranium qui ont été exploitées pendant 40 ans, mais qui sont maintenant fermées. Ensemble, les quatre zones contiennent environ 130 millions de tonnes de résidus, lesquels représentent une menace constante pour l'environnement à cause des contaminants radioactifs et, par conséquent, pour la santé humaine.

Dans ses présentations à la Commission fédérale, Santé Canada a abordé les questions de la protection contre les radiations, des dangers chimiques et des données épidémiologiques, notamment l'incidence du cancer.

** Veuillez noter que lorsqu'une présentation a été effectuée au Comité, la transcription réflète la langue dans laquelle a été présentée. Le sommaire du projet est présenté en français et en anglais.**

Le 16 novembre 1995, présentation de Santé Canada au Comité fédéral pour le déclassment des zones de gestion des résidus d'uranium à Elliot Lake en Ontario

Presentation by Mr. David Grogan, Health Canada

Thank you Mr. Chairman and other panel members for this opportunity to convey to you and the public the response of Health Canada to the Environmental Impact Statements of Rio Algom Limited and Denison Mines Limited concerning the decommissioning of the uranium mine tailings management areas for which they are responsible. At the outset I would like to say a few words outlining the responsibilities as Health Canada sees them under the Environmental Assessment and Review Process 1984 Guidelines Order (EARPGO).

For several years under EARPGO, Health Canada has supplied environmental health assessment information and advice requested by initiating federal departments. In addition and in line with EARPGO and the department's policies, the department has advocated the protection of human health as needed.

The Health Protection Branch of Health Canada has Regional evnironmental health assessment coordinators across Canada, and normally it would be the regional coordinator for Ontario who would be making this presentation to you today. However, the position is presently vacant and therefore it falls to me, as a member of the Office of Environmental Health Assessment in Ottawa, to make this presentation.

Scientists within Health Canada have reviewed the Environmental Impact Statements (EIS's) and the department has identified no significant health concerns associated with the proposals. The department, however, respectfully submits the following comments and recommendations which it hopes will be helpful to the panel when it formulates its recommendations.

Issues dealt with in this presentation are addressed in more detail in the departmental written submission given to the panel. It should perhaps be mentioned that Health Canada has previously commented at length on the panel Guideline conformity aspects of the proposal. Today's presentation takes into account these concerns, as well as the written responses subsequently provided by the proponents.

The Health Canada expertise relevant to the proposals under consideration covers the areas of radiation protection, chemical hazards, food, aboriginal affairs, epidemiological data collection, risk assessment and public risk perception.

Accompanying me today are two scientiests from the Department's Radiation Protection Bureau, which contributed significantly to the Health Canada submission. They are Dr. Peter Waight and Dr. Anar Baweja. They will assist me in addressing any subsequent questions.

Radiation Protection

In case of non-routine events, such as drought, the tailings may be exposed to air causing initiation of acid generation. Water augmentation plans do not come into operation until a water level depth of 5 cm is reached and incase of prolonged drought, water augmentation may become a significant proble, especially in the long term. Any seepages containing solubilized radionuclides and heavy metals will enter the Serpent River water system, impacting on the quality of water, sediments and biota (fish). Thus, human health will be impacted via ingestion of water, consumption of fish and game, and local produce. In view of the immense significance of water table depth, it is recommended that tailings dams and dykes be constructed high enough to maintain at least 1 m of water above the tailings surfaces.

Gamma surveys of tailings surfaces and the surroundings are described in Chapter 3 of both the main EIS's. Inadvertent intrusion by the public of the tailings surfaces may result in significant radiation dose to the intruders.

Rio Algom and Denison have proposed two gamma criteria for areas outside the WMAs/TMAs. These are 250 µR/hr peak levels with a 100 µR/hr grid criterion for site cleanup. It is understood by Health Canada that this cleanup criterion of 100 µR/hr was used at Port Hope, Ontario. In view of a recent compilation of background data, the average gamma radiation dose rate is 7.6 µR/hr, with a standard deviation of 1r µR/hr as reported by Tracy et al. at the 1995 Sixth International Symposium on the Natural Radiation Environment, held in Montreal. This natural background dose rate from cosmic and terrestrial sources gives an average dose of 666 µ/Sv/yr with a standard deviation of 100 µSv/yr.

A modelling approach has been used to calculate radiation doses from the ingestion of water, fisha nd game, and consumption of locally grown produce to the members of the public as well as the critical group. The estimates of radiation doses are generally satisfactory and it is agreed that all estimates are substantially less than the public dose limit of 1000 µSv/year proposed by the AECB. As previously mentioned, one concern is the intrusion scenario, which limits direct gamma exposure from the tailings to 200 hours per year. This is based on the optimistic assumption that institutional controls on land use will remain in effect for 1000 years. Health Canada would like to see a dose estimate for the case in which this assumption is removed.

Predictive modelling has been carried out for a 1,000 year period. According to the AECB Regulatory Document R-104, a time period of 10,000 years is recommended. This document states that a lesser time period may be acceptable provided an explanation is given. No such explanation has been given in the EIS's. In Health Canada's view, the long term radiological impact of the tailings is driven by the 1600-year half life of Ra-226. In the Denison EIS, the predicted Ra-226 concentrations in water at some receptor sites are actually higher than the present values. It is recognized that the model predictions may be less reliable after 1000 years, but it is recommended that some attempt be made to address the radiological impat in the time period 1000 to 10,000 years beyond the present.

Chemical Hazards

In large part, the approach used, and the materials presented support the conclusions reached regarding decommissioning options. Also the issues for the four tailings areas are similar, and can be dealth with in the same manner.

The major issues of interest to Health Canada are:

1. how was it concluded that chemical contamination was not important?;
   
   
2. were the exposure assumptions used valid?;
   
   
3. was the choice of decommissioning option adequately supported?; and
   
   
4. is the post-closure monitoring program adequate?
   

These will now be dealt with in order.

1. How was it concluded that chemical contamination was not important?
   
   The Environmental Impact Statements (EIS's) indicate that the only potential problem with chemical contaminants (metals in this case) is if the tailings are allowed to become acidic. All of the decommissioning options examined are designed to minimize this process, and option chosen (flooding or in situ management) is as good as any other for this.
   
   
2. Were the exposure assumptions valid?
   
   The use of some of the estimates of exposure (drinking water consumption, fish consumption) have been previously criticized by Health Canada as being too low. The reply to this criticism was that the proponent used Health Canada data for drinking water consumption, and a survey of the Serpent River Band for fish consumption. The survey of the Band for fish consumption is not published nor easily available for review, so that the quality of the survey cannot be determined. The use of point estimates for drinking water consumption and air intake reflect the means of the best data available. Their use in a probabilistic assessment such as this one is not proper however. While there is no problem using point values in a probabilistic assessment, values in the upper part of the range (95th percentile) are more proper. Use of mean values is recommended by Health Canada only for point estimates of exposure and risk for generic assessments and guideline development. Nonetheless, for these EIS's, it does not appear that the use of these point values would alter the conclusion reached regarding the potential impact of chemical contaminants and the resulting choice of decommissioning option.
   
   
3. Was the choice of decommissioning option adequately supported?
   
   The choice of flooding for decommissioning of the Quirke and Panel sites appears justifiable. While it is judged that there are some minor advantages to the soil cover option, they are not significant. The choices for Denison and Stanrock (flooding and in situ respectively) also appear justifiable. Alternate choices appear to have only minor (if any) advantages.
   
   
4. Is the post-closure monitoring program adequate?
   
   The time course of the post-closure monitoring programs is unclear. In some places it is indicated that anlaysis of water quality for metals will be conducted for only five years, while in others it is somewhere between 5 and 50 (EIS Summaries). This should be more clearly stated in the summary documents. The conclusions regarding water quality are dependent upon the estimates used for seepage rates from the proposed impoundments. These should be monitored very closely and certainly for longer than 5 years to ensure that the basis for non-impact on water quality is intact. Most of the conclusions regarding the impact (non-impact) of chemical contaminants is at least partially dependent on the engineerd component of the facility. As such it is vital that the predicted performance of the facility be obtained for the future, and that the integrity of the facility be maintained. These factors should be a major consideration in the analysis of the monitoring data.

Epidemiological Information

Cancer incidence data for the period 1986-1993 were supplied by the Ontario Cancer Treatment and Research Foundation. Statistically significant excesses were noted for Elliot Lake for colorectal cancer among femals and for lung cancer for both sexes. For lung cancer, there was a 124% excess among men and a 68% excess among women. For colorectal cancer there was a 65% excess among women. Conversely, it should be noted that prostate cancer risk was significantly lower than the provincial average.

The reason for the increased risk of colorectal cancer is not known. It is likely that the higher risk of lung cancer reflects, at least in part, the known high prevalence of cigarette smoking. Elevated lung cancer mortality has been observed not only in Elliot Lake, but across northern Ontario and throughout most of Quebec. It is likely that this also reflects the higher prevalence of cigarette smoking in these regions. The Ontario Health Survey revealed that the prevalence of cigarette smoking in the Algoma District was higher than the Ontario average, while numerous Labour Force Surveys have noted elevated cigarette smoking prevalence in Quebec.

Conclusions

Based on facility design and expected performance, chemical contaminants are not expected to be an issue

While some exposure parameters (e.g. drinking water consumption, air intake, fish consumption) are not properly used, they do not appear to impact negatively on the choice of the decommissioning option

The conclusion that chemical contaminants are not an issue is dependent upon the facility operating as expected. Monitoring of the performance is essential to ensure water quality is not adversely impacted.

No significant radiological impacts are anticipated from the decommissioning options chosen by the proponents.