The Safe Drinking Water Act (SDWA) was originally passed in 1974 to protect public health by regulating the nation’s public drinking water supply. It requires actions to protect not only drinking water but its sources, such as rivers, lakes, reservoirs, springs, and groundwater wells. The SDWA does not regulate private wells that serve less than 25 persons. The EPA sets the national health-based standards for drinking water to protect against man-made contaminants and naturally-occurring chemicals or substances that may be found in drinking water.

A number of threats can pose serious health risks to the public, including improperly disposed of chemicals; animal wastes; pesticides; wastes injected underground; naturally-occurring substances; and human threats.

The EPA, states, tribes, and water companies or systems work together to make sure standards are met. The SDWA applies to every public water system in the United States, but the most direct oversight of water systems is conducted by state drinking water programs.

The SDWA recognizes that since everyone drinks water, all persons have the right to know what’s in the water and its source. Water suppliers shall notify consumers quickly when a serious problem with water quality occurs. Water systems serving the same people year-round must provide annual consumer reports on the source and quality of their tap water.

All public water systems must have at least 15 service connections or serve at least 25 people per day for 60 days of the year. Drinking water standards apply to water systems differently based on their type and size:

Community Water System (CWS): A public water system that serves the same people year-round. Most residences including homes, apartments, and condominiums in cities, small towns, and mobile home parks are served by Community Water Systems.

Non-Community Water System: A public water system that serves the public but does not serve the same people year-round. There are two types of non-community systems:

Non-Transient Non-Community Water Systems: A non-community water system that serves the same people more than six months per year, but not year-round (i.e. a school with it’s own water supply).

Transient Non-Community Water System: A non-community water system that serves the public but not the same individuals for than six months (i.e. rest area or campground)

The SDWA defines “contaminant” as any physical, chemical, biological, or radiological substance or matter in water. Drinking water may reasonably be expected to contain at least small amounts of some contaminants, and their presence does not necessarily indicate that drinking water poses a health risk. Some drinking water contaminants may be harmful if consumed at certain levels while others may be harmless.

The Contaminant Candidate List (CCL) serves as the first level of evaluation for unregulated drinking water contaminants that may warrant further investigation. Only a small number of the overall contaminants are listed in the CCL.

The following categories are general drinking water contaminants:

• Physical contaminants primarily impact the physical appearance or other physical properties or water. Examples of physical contaminants are sediments or organic material suspended in the water or lakes, rivers, and streams from soil erosion.
• Chemical contaminants are elements or compounds. These contaminants may be naturally occurring or man-made. Examples of chemical contaminants include nitrogen, bleach, salts, pesticides, metals, toxins produced by bacteria, and human or animal pharmaceuticals.
• Biological contaminants are organisms in water. They are also referred to as microbes or microbiological contaminants. Examples include bacteria, viruses, protozoan, and parasites.
• Radiological contaminants are chemical elements with an unbalanced number or protons and neutrons resulting in unstable atoms that can emit ionizing radiation. Examples include cesium, plutonium, and uranium, which naturally breaks down in the ground to form radon.

Lead usually enters drinking water when lead-containing plumbing materials corrode. The most common sources are lead pipes, faucets, and fixtures. Lead service lines, pipes that connect the home to the water main, can also be a significant source of lead in drinking water. Lead pipes are more likely to be found in older cities and homes built before 1986. Fixtures with lead solder, such as brass or chrome-plated faucets, can also pose a health risk.

Corrosion is a dissolving or wearing away of metal caused by a chemical reaction between water and plumbing fixtures, and the extent of corrosion can be affected by a number of factors, including:

• the chemistry of the water (acidity and alkalinity)
• the types and amounts of minerals in the water
• the temperature of the water
• the amount of wear in the pipes
• the duration of water in the pipes, and
• the presence of protective scale or coatings inside pipes.

The EPA has set a maximum contaminant level of zero for lead in drinking water because lead is a toxic metal that can be harmful at low levels, it is persistent, and it can bioaccumulate in the body over time.

Young children, infants, and fetuses are particularly vulnerable to lead because its physical effects occur at lower exposure levels in children than in adults. In children, low levels of exposure have been linked to damage to the central and peripheral nervous system, learning disabilities, shorter stature, impaired hearing, and impaired formation and function of blood cells. The CDC recommends that public health actions be initiated when the level of lead in a child’s blood is 5 micrograms per deciliter or more.

Human skin is not known to absorb lead in water, so bathing and showering should be safe.