In the case of cancer-causing toxins, regulations are based on a level of risk that is acceptable, not a safe amount or concentration of a substance. Four Groups of Contaminants Microbial Pathogens. Pathogens in drinking water are serious health risks. They get into drinking water when the water source is contaminated by sewage and animal waste, or when wells are improperly sealed and constructed. The presence of coliform bacteria, which is generally a harmless bacteria, may indicate other contamination to the drinking water system.
People worry the most about potentially toxic chemicals and metals in water.
Only a few of the toxic organic chemicals that occur drinking water are regulated by drinking water standards. Pesticides, including herbicides, insecticides, and fungicides. Possible chronic health effects include cancer, central nervous system disorders, liver and kidney damage, reproductive disorders, and birth defects. These contaminants include toxic metals like arsenic, barium, chromium, lead, mercury, and silver. These metals can get into your drinking water from natural sources, industrial processes, and the materials used in your plumbing system.