The sources of drinking water (both tap and bottled water) include rivers, lakes, streams, ponds, reservoirs, springs, and wells. As water travels over the surface of the land or through the ground, it dissolves naturally-occurring minerals and radioactive material, and can pick up substances resulting from the presence of animals or from human activity.
Contaminants that may be present in source water include:
• Microbial - viruses and bacteria, which may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife
• Inorganic - salts and metals, which can be naturally-occurring as a result of urban runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming
• Pesticides or herbicides - may come from a variety of sources such as agriculture, storm water runoff, and residential uses
• Organic chemical - includes synthetic and volatile organics, which are by-products of industrial processes and petroleum production, and can also come from gas stations, urban storm water runoff, and septic systems
• Radioactive contaminants - can be naturally-occurring or be the result of oil and gas production and mining activities
In order to ensure that tap water is safe to drink, the EPA prescribes regulations that limit the amount of certain contaminants in water provided by public water systems. FDA regulations establish limits for contaminants in bottled water, which must provide the same protection for public health.