Exposure and Preliminary Health Assessments of the Oujé-Bougoumou Cree Population to Mine Tailings Residues: Report of the Survey
The Cree community of Oujé-Bougoumou is located approximately 60 kilometres west of Chibougamau and comprises 622 residents. There was, for this community, a potential exposure to toxic substances derived from tailings residues left behind from mining operations in the mid 1950s.
Confronted with this potential exposure, the Grand Council of the Crees commissioned an environmental contamination study, which was conducted by Christopher L. Covel from CL COVEL PG LLC and Roger D. Masters from Dartmouth College, Hanover, New Hampshire. This study indicated mobilization of toxic elements from mine tailings residues and suggested possible impacts on human health.
The report produced by this study was subsequently critically reviewed by Evert Nieboer of McMaster University who endorsed the environmental conclusions, but not the interpretation of the data on contaminants in hair on which the human health risk judgement had been based. A 2001 survey by the Quebec Ministry of the Environment confirmed the presence of toxic elements in sediments near mine tailings sites. Subsequently, the Oujé-Bougoumou Council accepted E. Nieboer’s recommendations that an environmental risk assessment and a human health study be initiated.
To address the Oujé-Bougoumou community’s needs, the ministry of Health and Social Services mandated the Quebec National Institute of Public Health to conduct a study in order to characterize the possible exposure of the Cree community of Oujé-Bougoumou to environmental toxic elements. This report presents the data of the project conducted during the autumn of 2002 in the Cree communities of Oujé-Bougoumou and Nemaska.
The main objective of this study was to assess the exposure of the Cree community of Oujé-Bougoumou to various toxic elements associated with mine tailings residues. At the same time, the study goal was to measure a battery of clinical chemistry parameters that can be used in the assessment of the general health of the population.
Three specific objectives were defined in the scope of this study. The first one consisted of assessing human exposure to inorganic elements associated with the mine tailings (arsenic, copper, selenium and zinc), life-style issues (lead and cadmium) or persistent pollutants often associated with fish consumption (e.g., mercury and PCBs). The second specific objective aimed to compare the biological contaminant exposure results with reference data obtained concurrently in a control Cree community (Nemaska), as well as with the concentrations observed in a Southern Quebec population previously studied and those recommended (published) as reference ranges. Finally a third specific objective was to measure and interpret an array of biochemistry parameters of clinical interest that relate to individual and/or general health.
Populations under study
A total of 225 participants in Oujé-Bougoumou (the study community) and 100 in Nemaska (the control community) participated in the study. Age and gender subgroups were considered in the recruitment and the different groups were respectively composed of children aged between 0 and 14 years old, women 15 to 39 years, men 15 to 39 years, and men and women over 40. The number of study subjects in each group but the second was proportional to the age distribution in each community.
Three questionnaires were designed, tested and adapted for the specific purpose of this study. In the exposure/life-style questionnaire, questions were posed about the following issues: general socio-demographics and residency, specific information about the household property, occupational details, outdoor activities and hobbies and questions concerning life-style issues, stress and psychological well-being. The food frequency questionnaire addressed the consumption of traditional subsistence and the health questionnaire self-reported health outcomes.
Blood, urine and hair samples were collected and levels of contaminants and clinical biochemistry parameters were determined employing proven laboratory measurements.
Cardiovascular disease (CVD) risks factors such as obesity, cigarette smoking, and diabetes were found to be frequent in both communities. Only diabetes was more frequent in Oujé-Bougoumou. Fish consumption was associated with a more favorable omega-3 fatty acid status and appeared to improve the CVD risk factors of low level of plasma HDL cholesterol, high level of LDL cholesterol and high level of total cholesterol.
Folate, vitamin B12, thyroid stimulating hormone (TSH) and free thyroxin (T4) levels were essentially in their normal ranges and not different between the two communities.
Total fish consumption was comparable in both communities, but predatory (piscivorous) fish were favoured in Oujé-Bougoumou, while insectivorous fish were more often consumed in Nemaska. Game offal was eaten more frequently Oujé-Bougoumou.
Inorganic and total arsenic concentrations in urine were generally higher in Nemaska than Oujé-Bougoumou. Exceedances of the normal reference range of copper in plasma occurred, as expected, among pregnant women and those taking oral contraceptives. Copper in urine and hair were significantly higher in Oujé-Bougoumou females of reproductive age. Selenium in plasma was higher in Nemaska than Oujé-Bougoumou, and this likely reflects differences in dietary habits. Zinc in plasma was higher in Oujé-Bougoumou and might also reflect differences in dietary habits.
Cadmium level in whole blood of all participants was 2.5 to 3.0-fold higher compared to the Southern Quebec comparison group. Smoking was the main factor, but exposure through consumption of game liver and kidney remains plausible. Lead whole-blood concentrations were lower in both Cree communities compared to other native communities, but exposure was still related to hunting and consumption of wildfowl and game.
Mercury exposure in the two Cree communities may be termed mild to moderate and was comparable to levels found in Canadian Inuit populations and was related to fish, bird and game consumption; the observed hair-to-blood mercury ratio was 242:1. PCBs exposure might be designated as moderate to high and was related to fish and game consumption. Liver enzymes and levels of TSH were normal among the most exposed individuals (>100 μg/L of total PCBs). Exposure to DDT and its metabolite DDE was high in the over 40 age group, especially in Ouje-Bougoumou, and was dependent on the consumption of fish and game. The DDE/DDT ratio was 57+U33, suggesting little current use or sources of DDT. Concentrations of persistent contaminants were generally higher in the over 40 age group and reflect the role of diet as a major source of exposure.
Based on the observed concentrations of the signature elements arsenic, copper, selenium and zinc in body fluids, we conclude that the residents of Oujé-Bougoumou are not at risk of internal (systemic) exposure. Hair levels of the mine tailings signature elements were moderately elevated in Oujé-Bougoumou relative to Nemaska and a possible indirect source through chronic low-level contact might be explored in the case of arsenic and copper.
Cigarette smoking is the major source of exposure to cadmium in both Oujé-Bougoumou and Nemaska. Lead exposure is related to hunting activities and consumption of wildfowl and game in both Cree communities.
Exposure to mercury and PCBs was higher in Oujé-Bougoumou than in Nemaska; higher consumption of piscivorous (predator) fish such as walleye and trout might be the explanation. The observed concentrations of the p,p’-DDE (a metabolite of the insecticide DDT) are found to be relatively high in the over 40 age group, especially in Oujé-Bougoumou.
In both communities, the status of the essential elements copper, selenium and zinc are judged to be normal and adequate to sustain proper health. The iron status also appears adequate.
No new information about health status was identified in the two study communities.
The impact on the general environment of the elements related to mine tailing residues should be assessed as part of the ongoing environmental risk assessment, even though there is no evidence of unusual intake by humans.
The source of the organochlorines PCBs and DDT/DDE should be investigated as part of the ongoing environmental risk assessment.
Replacement of leaded ammunition should continue to be encouraged.
It is recommended that consumption guidelines for subsistence foods be reviewed, updated and their use by the Cree communities should continue to be promoted. The following factors should be incorporated into a more formal consumption guideline program. Routine monitoring of local fish tissues, as well as kidney, liver and fatty tissues of game and of piscivorous fowl, should be initiated. Consumption guidelines should be based on the biomonitoring results obtained for fish caught in local lakes and rivers and for wildfowl and game bagged in the communities’ hunting grounds. The importance of consuming traditional foods to maintain health should be considered in the risk management.
The regular consumption of game liver and kidney should be avoided since a concern arises because persistent contaminants accumulate in kidney (especially cadmium) and in liver (e.g., cadmium, mercury and PCBs).
Anti-smoking interventions are likely to yield significant health benefits.