There’s actually a huge, testing process that all public water systems in the United States undergo in order to determine the safe drinking water standards.
In the U.S., The Environmental Protection Agency (EPA) is charged with establishing standards to ensure drinking water is safe. In 1974, Congress enacted the Safe Drinking Water Act (SDWA) in order to ensure that drinking water is safe for public consumption. According to the EPA’s website, there are currently more than 160,000 public water systems that will provide water to Americans at some time in their lives.
Today, the EPA is required to set drinking water quality standards, also known as maximum contaminant levels (MCLs), enforceable in all states and localities for public water suppliers. MCLs represent the maximum concentration levels that are allowed in public drinking water systems. Currently there are fewer than 100 contaminants that have been established as ‘high-risk.’ Besides being based on heath risks, these MCLs are also based on “treatment technologies, costs (affordability) and other feasibility factors, such as availability of analytical methods, treatment technology and costs for achieving various levels of removal,” according to the EPA’s website.
It should be noted that these standards apply to pubic systems and NOT to individual homeowner drinking water sources such as private wells. These sources are generally not regulated but need to meet health-based standards to be considered potable.
The EPA currently provides standards for safe drinking water in public systems and continuously evaluates these to ensure that standards are based on the best available science.
The list of contaminants selected by the EPA represent the most common and/or harmful contaminants expected to be present in drinking water. All public water suppliers must ensure that treatment removes these contaminants to below their applicable MCLs. However, they cannot regulate every contaminant often because of costs and technology limitations as well as limited knowledge as to the health effects of the millions of chemicals yet to be studied.
There are many websites with information about drinking water quality and the standards set in place to help protect human health.
Residents utilizing a public water source can view the water quality reports for their specific area which are required to be provided to customers annually and available as public information. Further, this information is generally available on the water company’s website.
In addition to the information on the EPA website, private well owners can look to their state’s regulatory agencies (ie: Department of Environmental Protection) for more information. For example, even though the Pennsylvania Department of Environmental Protection does not regulate private homeowner wells in Pennsylvania the agency provides information about proper well construction, common contaminants and other publications on water quality.