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Threats to Sources of Drinking Water and Aquatic Ecosystem Health in Canada

Executive Summary

1. Waterborne Pathogens

Freshwater bodies require protection from pathogens that pose threats to drinking water supplies, recreational waters, agricultural and aquacultural source waters, and to aquatic ecosystems in general.Waterborne pathogens can pose a problem to drinking water supplies, recreational waters, and source waters for agriculture, and aquaculture. Sources of pathogens include municipal wastewater effluents, urban runoff, agricultural wastes and wildlife. A drinking water incident in Milwaukee in 1993 killed 54 people and made 400,000 sick. From 1974 to 1996 there have been over 200 outbreaks of infectious diseases in Canada associated with drinking water. Pathogen contamination of irrigation water or shellfish beds can also pose risks to human food supplies. In addition, declines in amphibian populations may be related to fungal or viral pathogens. There is a need to study the consequences of environmental releases of microbial pathogens because there is inadequate knowledge of the sources, occurrence, concentrations, survival and transport of specific microorganisms in the environment. Enhanced funding is needed to validate newer molecular detection tools, understand the ecology of pathogens in aquatic ecosystems, better predict disease outbreaks, and improve emergency responses. A preventive approach to pathogen pollution should be taken by Canada in the form of a source water protection program for all major freshwater bodies.

2. Algal Toxins and Taste and Odour

Toxic blue-green algae bloom in Hamilton Harbour, Ontario, August 2001.Algal toxins in stock watering sources have killed animals and may affect their health. In Brazil, 50 people died due to algal toxins in water used for hemodialysis in 1996. Toxins can attack the liver, the nervous system or irritate skin, yet very few of these toxins have been isolated and characterized. Reliable prediction of blue-green algal blooms is rare but is thought to be related to nutrient loads. Taste and odour problems in potable water are increasing worldwide and are produced by microorganisms such as bacteria and fungi. However, the toxicological properties of taste and odour compounds are scarcely known. Taste and odour problems occur in British Columbia, the Prairie provinces, Ontario and Quebec, and their frequency is increasing. Because toxins in raw and finished water are poorly studied, there is a need to know seasonal trends in their concentration and production. The triggers for toxin-producing algal blooms need to be better understood. There is likewise a lack of knowledge of the sources and triggers of taste and odour compounds. Also, little is known of the chemistry and biological fate of taste and odour compounds, and potential health effects from their consumption, dermal contact and inhalation should be checked. Treatment technologies for drinking water plants should be optimized to deal with algal toxins and taste and odour causing compounds.

3. Pesticides

Groundwater and surface water contamination by pesticides will likely intensify in the future, necessitating a better understanding of their sources, fate and effects, and degradation products.Synthetic chlorinated pesticides were introduced in the 1940s and 1950s but serious environmental problems only began to be noticed in the 1960s and 1970s. There are 550 pesticide active ingredients currently registered in Canada under PCPA, and PMRA is committed to re-evaluating 400 older pesticides (registered before 1995). Groundwater and surface water contamination by pesticides will likely intensify. Thus, a better understanding is needed of the sources, fate and effects of pesticides and their degradation products. Unfortunately, there is a lack of a coordinated, interjurisdictional system for monitoring pesticides in Canada. With climate change, changing agricultural practices may change pesticide use patterns. Also, the introduction of new pests to Canada may require increased targeted pesticide use. In addition, the toxicological significance of constant exposure to low levels of pesticides is unknown and research is also needed on the chemical analysis of ultra-low levels of pesticides. With recent advances in GMOs, there is a need to determine hazards of genetically expressed pesticides in crops. Research is needed on risk assessment methodologies and into the effectiveness of risk mitigation and risk management options.

4. Persistent Organic Pollutants and Mercury

A trapper with the Holman Society, fishing for lake trout and arctic char through the ice on Uyaaktuk Lake near Holman, Northwest Territories. Studies show exposure to contaminants through high rates of fish consumption causes disturbances in reproductive parameters and neurobehavioural and developmental deficits in newborns and older children.Persistent organic pollutants (POPs) comprise a group of chemicals that degrade slowly in the environment, bioaccumulate and have toxic properties. Substantial historical reservoirs exist for many POPs in the Canadian environment. Mercury (Hg) is a natural element but behaves like a semi-volatile organic compound and is transported through the atmosphere almost entirely as gaseous mercury. Great Lakes and Arctic communities with high consumption of fish, even with low levels of POPs and Hg, can exceed tolerable daily human intakes. In biota, there has been a twofold increase from 1975 to 1995 in Hg in thick-billed murre eggs in the Arctic. New compounds such as flame retardants are used in the manufacture of plastics, paints, textiles and electrical devices. There has been a 65-fold increase between 1981 and 1999 of flame retardants in Lake Ontario gull eggs. Because several older pesticides can be detected in sites far removed from areas of former use, long-range atmospheric transport is indicated. Research is needed on the toxicology of individual compounds of POPs such as toxaphene and basic physical property information is needed on new POPs, especially at temperatures relevant to Canada. The capacity to link chemical measurements of POPs to biological effects needs to be strengthened. Models to predict the trends in environmental levels of old and new POPs need to be refined. There is still uncertainty about anthropogenic versus natural sources of Hg and detailed investigations of the Hg biogeochemical cycle are needed. Development of capacity to precisely measure stable isotopes of Hg is needed to help resolve the natural versus anthropogenic source questions.

5. Endocrine Disrupting Substances

Intensive agriculture is one of the major causes of endocrine disruption in the Canadian environment.Endocrine Disrupting Substances (EDS) can exert an array of effects on growth, development and reproduction in biota at extremely low concentrations and these effects can be expressed in future generations. EDS include drugs, pesticides, industrial chemicals, metals and natural compounds, and are found in municipal, agricultural, textile, pulp and paper, and mining effluents. The effects of EDS include deformities and embryo mortality in birds and fish and they depress thyroid and immune functions in fish-eating birds. Cognitive and neurobehavioural effects in infants can be related to prenatal exposure to EDS. EDS will thus continue to be a high-profile international issue. Priority research should go to sites, sectors and populations having the highest potential for effects and should focus on functional endpoints of growth, reproduction and development during critical life stages. Environmental and human health monitoring programs should be enhanced. Laboratory testing needs to be related to ecological significance in the environment and work with international agencies is required to validate currently proposed tests for EDS effects. Better knowledge is needed of low-dose effects and thresholds, and a framework for risk assessment of EDS in mixtures and effluents should be developed. A weight-of-evidence approach should be used to make appropriate decisions.

6. Nutrients--Nitrogen and Phosphorus

Available nitrogen and phosphorus have increased dramatically in the past few decades, with widespread environmental consequences.Nitrogen (N) or phosphorus (P) limited productivity in aquatic ecosystems prior to human settlement and development of agriculture. Today, the amount of N and P available for plant uptake has increased dramatically and available N has doubled since the 1940s and human sources of P greatly overshadow natural sources. These increases in N and P can accelerate eutrophication of surface waters and wetlands, and increase the frequency of toxic algal blooms leading to risks to humans. The nitrate drinking water guideline is exceeded in groundwater in many parts of Canada. Nutrient losses from intensive livestock operations are likely to rise and aquaculture is a growing source of nutrients to surface waters. Knowledge is needed on how nutrients induce algal blooms and toxin production and the role of nutrients in causing taste and odour problems. Effects of forestry and agricultural land use on nutrient losses need to be assessed. The relationship between nutrients and aquatic plant biomass in streams is not understood. Nutrient guidelines are needed to protect aquatic life in different water bodies, with nutrient management plans and codes of practice developed for sectors such as agriculture or aquaculture, and watershed management plans for specific basins.

7. Aquatic Acidification

Sampling to quantify stream chemistry.For many years, Canadian research has been in the vanguard of defining the aquatic effects of acid rain. Scientific consensus justified SO2 and NOx emission controls in Canada and internationally, and both Canada and the U.S.A. have significantly reduced SO2 but not NOx emissions. Reproduction and death of fish species are linked to low pH with resultant effects on aquatic birds due to changes in quality and quantity of food. Given present SO42- deposition, critical loads will still be exceeded for most of Canada's monitored lakes, while there have been few cases of natural recovery of fish communities. In southeastern Canada, some 76,000 lakes will remain chemically damaged unless additional SO4 2- emission reductions are continued. New surveys must be conducted if assessment of changes is to be made. Meanwhile, the nitrogen status of lakes and catchment basins remains unknown. The status of the soil base cation pool and its replenishment rate, and the size and reactivity of the stored sulphur pool are also unknowns. Models should be modified to include nitrogen-based acidification. In situ assessment of the toxicity of acidification episodes needs to be conducted. The interactions of acidification recovery with future climate change also need to be assessed.

8. Ecosystem Effects of Genetically Modified Organisms

Large-scale field trials are needed to determine the impacts of genetically modified organisms in agriculture and silviculture.The use of genetically modified organisms (GMOs), specifically genetically modified (GM) crops, began in the 1990s in Canada, has grown significantly, and is projected to continue to do so. The only GMOs registered in Canada to date are microbes for sediment remediation and GM crops. So far, there have been no attempts to register GM fish or GM trees. Nevertheless, there is already a need to know the long-term cumulative impacts on biodiversity resulting from the dispersal of GMOs in the environment. We need to know the uncertainty involved in current short-term, small-scale risk assessments carried out by regulators and develop adequate predictive capacity in extrapolating from the lab or small plot scale to much larger scales. The potential impacts of engineered insecticidal residues on soil and stream microorganisms and invertebrates is also unknown. The most sensitive diagnostic molecular biological tools should be used to answer these questions.

9. Municipal Wastewater Effluents

Municipal wastewater effluents are composed of suspended solids, human waste, debris and chemicals from residential, industrial and commercial sources.These effluents (MWWE) are a complex mixture of human waste, suspended solids, debris and a variety of chemicals derived from residential, commercial and industrial sources. They comprise the largest source of effluent discharge to Canadian waters, and population growth and urbanization will continue to increase them. MWWE are a source of endocrine disrupting substances, pharmaceutical, and personal care products, among other contaminants. There is a need to better understand the sources, fate and distribution of priority and toxic substances in municipal treatment systems. Sludges generated at municipal wastewater treatment plants are applied to lands and their impact on surface and ground water needs to be assessed. Waste treatment and disposal quality criteria, objectives and standards should be based on the assimilative capacity of the receiving waters. Municipal wastewater planning should be integrated as part of overall watershed planning.

10. Industrial Point Source Discharges

Pulp and Paper

A field-based artificial stream system can be used to assess the ecological effects of mining, petrochemical and pulp and paper effluent discharges on riverine systems.In the year 2000, there were some 125 pulp and paper mills across Canada and a typical mill generates some 90 to 130 million litres of effluent per day. The effects of these effluents consist of chronic toxicity to aquatic organisms and eutrophication. Although the volume of pulp mill effluents is expected to decrease, concentrations may increase. Colour and taste and odour have been detected 900 km downstream of pulp mills. Of the mills in Canada, 80% report effects of effluents on fish.


There are 900 present or former mining sites for base metals, gold, potash, coal and iron ore across Canada and most sites are adjacent to freshwater systems in remote areas. At active mines, concerns include chronic effects of metals, bioaccumulation, sediment contamination, and endocrine disruption and closed or abandoned mines also contribute contaminants to local water systems. Many new mines are anticipated in remote, sensitive environments such as the Arctic.


Petrochemicals are extracted by oil and gas drilling and oil sands mining. Although there are few direct effluent discharges to water due to extraction, with the exception of the oil sands, petrochemical refineries are located on water bodies that can provide cooling water. Many petrochemical by-products are toxic, hydrophobic and persistent, and adjacent water bodies often contain highly contaminated sediments. Long-term implications for aquatic biota in waters receiving Oil Sands Process Waters are unknown while the oil sands are expected to triple production over the next 20 years.

The implications of pulp mill discharges to drinking water quality are still largely unknown because the identity of causative agents such as EDS remain unknown. There is a need to distinguish natural effects from industry-related effects and to include drinking water endpoints in ecological assessments of water quality for all industrial discharges. An ongoing monitoring program, similar to the EEM for pulp and paper mills, is also needed for the mining and petrochemical industries. There is a need to develop cumulative effects assessments and emphasize integrated watershed management. Ecologically based assessment criteria should be incorporated into environmental management strategies. Development of novel technologies to reduce impacts of effluents on water quality should be encouraged.

11. Urban Runoff

Flooding and erosion impacts of urban runoff can be lessened by effective stormwater management.Urban runoff transported by sewers, drainage channels and streams is ultimately discharged to receiving waters. Urban runoff is a mixture of storm water, raw sewage and scoured sewage. Impacts on human health are through contamination of source drinking water, fish and shellfish, recreational water, and breeding grounds for disease vectors such as encephalitis. Current practices of urban development are not sustainable with respect to receiving water quality. Infectious diseases may inhabit urban wetlands used to control runoff. There is a need to better understand the sources, pathways and fate of contaminants and microbial pollutants in the complete urban environment. There is a need to update data on the composition of storm water runoff. Total urban water cycle management is required and protocols are needed for the protection of urban water supplies from all hazards. National standards should be developed for the design and operation of urban water systems.

12. Landfills and Waste Disposal

Abandoned mines are one of the sources with potential to release heavy metals and other contaminants into ground and surface waters.Canada ranks among the highest producers of solid waste in the industrial world. These wastes are produced from domestic, commercial, industrial and agricultural activities. Drinking water sources in groundwater-dependent communities like Elmira, Ontario; Abbotsford, B.C.; and Ville Mercier, Quebec, have been contaminated by poor waste disposal and groundwater contamination can damage drinking water supplies for decades to hundreds of years. Nutrients, metals, and volatile organics are often detected in aquifers several kilometres from landfill sources. Effects of mining wastes have been projected to last decades to centuries to millenia. Contaminants in livestock waste include nitrate, ammonia, coliform bacteria, phosphorus, endocrine disrupters and pharmaceuticals. Biosolids from sewage treatment plants are disposed of in landfills and spread on land and contain the same contaminants as animal wastes. As Canada's urban population grows, so does the amount of municipal waste, and the number of septic systems will continue to increase dramatically. Also, the importation of hazardous wastes from other countries has increased. Meanwhile, there are gaps in knowledge of the mobility of new chemicals such as POPs and EDS in landfills; transport of contaminants across the groundwater-surface water interface; and long-term release of nutrients and metals from biosolids. There needs to be effective implementation of aquifer remediation and treatment systems. New regulations rather than guidelines for waste disposal are needed along with harmonization of regulations and guidelines among all levels of government. Realistic bonding should be in place to deal with long-term problems and abandoned sites.

13. Agricultural and Forestry Land Use Impacts

Timber harvest and agricultural practices affect the quantity and quality of runoff water.In Canada, approximately 12% of the total land base is currently managed for timber harvest, another 7% is used for farming and an additional 1% is in urban/industrial development. Timber harvest can increase water yield, suspended solids and temperature in streams; disrupt the cycle of nutrients between the soil and trees; and increase concentrations of dissolved nitrogen, organic carbon, base cations and phosphorus in streams and lakes. Although timber harvest is expected to continue in order to meet market demand, hydrologic, chemical and biological impacts on streams and lakes from forest management practices have been defined for relatively few sites. Intensification of agricultural production has increased the risk of water contamination unless substances such as mineral fertilizers, pesticides and manure are adequately managed. Pesticides are frequently detected in surface waters draining cropland. There is a need to study the environmental and human health consequences of nutrient, pathogen, pharmaceuticals and endocrine disrupting substances added to surface and ground waters from agricultural practices. There is inadequate knowledge of biogeochemical and hydrological cycles to predict the effects of changes in agricultural and forestry land management practices on water resources. Enhanced funding is needed to validate newer molecular detection tools, understand the ecology of pathogens in aquatic ecosystems, better predict disease outbreaks, and improve emergency responses. Scientifically credible practices, standards, and codes for agriculture and forestry operations, together with appropriate enforcement mechanisms, should be established to ensure protection of ground and surface waters and aquatic biota.

14. Natural Sources of Trace Element Contaminants

Water is the principal vehicle for transfer of dissolved trace element contaminants.Natural geologic sources of trace element contaminants exist in many regions of Canada. These sources threaten groundwater and surface waters. For example, on the Prairies, arsenic in groundwater is locally above safe limits; in the Moncton area, fluoride levels are high; and naturally high levels of radioactivity and radon are associated with granitic terranes. Mapping of the geologic sources of contaminants shows clearly where some anomalies exist, but is far from complete. There is thus a need for further mapping of the geochemical landscape, research on speciation and bioavailability of trace elements, and a horizontal approach among agencies to determine the severity of the threat.

15. Impacts of Dams/Diversions and Climate Change

Ice breakup on the Mackenzie and Liard rivers: historical sources show earlier ice breakup and later freezing dates on lakes and rivers in recent years.Impacts of water quantity changes on water quality are based largely on studies of the effects of Canada's 600 dams and 60 large interbasin diversions. Changes to water quantity modify various water-quality parameters within the reservoir and downstream and flow diversions also produce major changes in water quality. Variations in climate can produce major changes in both water quantity and quality. For example, historical sources show earlier ice breakup and later freezing dates on lakes and rivers in recent years. The Canadian climate will be increasingly warmer and wetter. In the Great Lakes basin there will be reduction in annual streamflow and lake levels, but an increased frequency of flood events. In some areas, the current sewage treatment facilities are unlikely to accommodate the increased volume of stormwater and sewage runoff. The Prairies will experience the most pronounced drying of any region in Canada. In such semi-arid regions, first-order streams may become ephemeral, many ponds and wetlands will completely disappear and lakes will become disconnected. There is a need to improve climate forecast scenarios, and down-scale global models for use in hydrological and ecological models. Better understanding is required of the interactions between hydrological processes and biogeochemical responses; effects of changes in water quantity/quality on ecosystem structure and function; and interaction between changing hydrologic regimes and aquatic habitat quality. Knowledge is needed about water balances in altered landscapes and better methods are needed to predict how changes in the climate system affect the hydrologic cycle. Instrumented basins should be established or enhanced in representative regions and a Canadian Hydro-Ecology Research Network established.

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