Some of these substances accumulate through the food chain rather than break down in the environment. Toxic substances in the food chain Excess nutrients such as nitrogen and phosphorous compounds come mainly from municipal sewage and farm run-off containing fertilizers and animal waste. These nutrients can cause excess growth of aquatic plants, which then die and decay, depleting water of dissolved oxygen and killing fish. Sedimentation is an increase in the amount of solid particles in water, caused primarily by human activities such as forestry, farming and construction. When sediment settles, it can smother the feeding and dspawning grounds of fish and kill aquatic organisms.
Water pollution has wide-ranging impacts on our health, our environment and our economy.
Some toxic substances in our water are known to cause cancer. Others are harmful to reproductive and immune systems and have been detected in the breast milk of mothers. While all Canadians are affected, the greatest health risk is to small children, the elderly and to Aboriginals in the north who rely on local wildlife as a source of food. In addition to pollution concerns, governments are involved in a wide range of water issues ranging from the predicted impacts of climate change, to flooding, droughts, bulk water removals, and interbasin water diversions. Population growth has also accelerated pressures on our water supplies, and on the natural water and wetlands systems upon which our freshwater supplies depend.