Biochemical Oxygen Demand
Toxicants cannot be controlled except at great cost at the point of entry into the water but must be regulated earlier in production. Different toxicants present different regulatory possibilities and problems. For example, PCBs (polychlorinated biphenyls) have to be controlled at the point of manufacture to limit dispersal; valuable materials (eg, chromium, lead) can be recycled economically; some toxicants can be replaced by nontoxic substitutes (eg, replacement of cyanide rinses in electroplating). Municipal and industrial treatment processes generally place toxic materials in sludges, which must then be treated or stored. Acidification can be prevented effectively only by controlling discharges of both nitrogen and sulphur oxides into the atmosphere. Temperature changes can be prevented only by dissipating heat into the atmosphere by air cooling.
Canada's rich endowment of fresh and marine water is threatened by regional shortages (eg, southern Saskatchewan and Alberta) and by serious pollution (eg, Great Lakes). Although pollution from pathogens, BOD and waste heat may be relatively easily reversed, eutrophication and oil spills are more difficult, and acidification and toxicity may be irreversible. Thus, control policies at all levels of government are increasingly emphasizing the regulation of toxicants and the early detection and prevention of pollution.
Author ANTHONY H.J. DORCEY
Links to Other Sites
Glossary: Environment and Sustainable Development
An extensive glossary of terms related to environmental and sustainable development issues.
Explore this Webby award-winning website about the ills besetting the waters of the Great Lakes. From the National Film Board of Canada.
Bedford Institute of Oceanography
The website for the Bedford Institute of Oceanography. Features many research reports, maps, diagrams and multimedia resources about oceanography. Also profiles the Canadian Coast Guard survey vessels stationed at the Institute. Check the informative “Program Overview” before searching this very extensive site.
Climate change blamed for rising mercury levels in whales
A CBC News article about evidence of rising mercury levels in whales.
Mercury and Human Health
Information about sources of mercury in the environment, health effects of mercury exposure, the risks of mercury poisoning, and related issues. From Canada’s Minister of Health.
A glossary of commonly used terms relating to geography, agriculture, and the environment. A Government of Manitoba website.
Health Canada to test taps for cancer contaminants
This CBC News article identifies several contaminants in tap water tested by Health Canada.
Glossary: Great Lakes
A glossary of key environmental terms and programs related to the Great Lakes. From the University of Minnesota in the US.
Glossary: Water Resources
An extensive glossary of terms related to the use and management of water resources. Check the rest of the site for additional information. From the North American Lake Management Society.
Glossary: Waste Treatment
A glossary of terms related to waste treatment processes. From the website for the Capital Regional District, located on Vancouver Island.
Glossary: Lake Ontario-St Lawrence River system
A glossary of key terms related to environmental issues in the Lake Ontario-St Lawrence River system.
Glossary of Water Management Terms
A glossary of terms related to pollutants found in the Canadian North. From the Department of Aboriginal Affairs and Northern Development.
Glossary: Environmental Management and Water Pollution
A glossary of terminology related to environmental management and water pollution. A Government of Yukon website.
Science and Technology into Action to Benefit Canadians
"S&T into Action to Benefit Canadians" tells the story of Environment Canada's success in generating tangible environmental, social and economic benefits. From Environment Canada.
Earth Day Canada
Check out the website for Earth Day Canada for local Earth Day events in your community. Find out what each of us can do to lessen our environmental impact.
See online illustrated magazine articles about programs designed to deal with the demand for clean fresh water around the world. From Diplomat & Internations Canada.