Contaminated water stems from a variety of sources and results from increased levels of road salt, household fertilizers, chlorine, lead, mercury, microorganisms and the leaching of organic and inorganic materials.
Every winter, road salt used to melt ice ends up in groundwater, increasing risk of hypertension in humans. Recommended sodium levels are 10-20 mg/L, but sodium runoff into reservoirs yield values that exceed 1000 mg/L. Increased road salt levels has also been linked with pipe corrosion that leaks unwelcome minerals into tap water.
Household fertilizers and detergents containing nitrogen and phosphorus drain to rivers from wastewater treatment plants and from local areas such as golf courses. Levels of phosphorus and nitrates above 0.1 mg/L cause eutrophication in lakes and rivers, causing oxygen depletion, killing fish and contributing to water toxicity. The chlorination of water is used worldwide to eliminate parasites and other microorganisms, however, chlorine in excess of 250 mg/L has been linked to cancer, kidney problems and heart disease and is toxic to commercial fish. Unfortunately, it is not possible to detect chlorine in water by taste alone until it exceeds 1000 mg/L. Road salt also contributes to chlorine runoff.
Sources of lead pollution is often linked to old lead-lined pipes that leak the element into tap water. The highest level of lead allowable under EPA standards is 0.015 mg/L.
Effluent from pulp and paper mills results in mercury contamination. While mercury is not soluble in the human body, mercury compounds such as methylmercury result when mercury passes through the digestive tracts of fish and mammals. Methylmercury readily bioaccumulates in organisms and ingestion by humans has been liked to irreversible brain damage. Microbes that commonly end up contaminating drinking water are fecal coliform and E. coli bacteria, Cryptosporidium, and Giardia lamblia. The presence of these microbes indicates water contamination by human waste, animal waste or sewage leaking into clean water sources. Side effects of microbe contamination include short term nausea, headaches, diarrhea, vomiting and cramps, but for those with compromised immune systems, intestinal infection with the parasite Cryptosporidium can be fatal. Ascaris is another common parasite whose eggs contaminate water in underdeveloped countries.
Water contamination through organic and inorganic materials readily causes nervous system damage, cancer, birth defects and kidney and liver problems. These effects may be much more pronounced in children affected by contaminated water; EPA maximum contaminant level guidelines are based off of adults weighing approximately 175 lbs.