Water Quality Standards

There are two types of water quality standards in the United States. The first type of standard is used to ensure that water is safe to drink or ingest. These standards are called Primary Drinking Water Standards and are enforced by law. The second type of standard is to ensure that water is functional and aesthetic for various uses such as bathing and washing. These standards are re­ferred to as Secondary Drinking Water Standards, and they are voluntary.

The Environmental Protection Agency (EPA) establishes drinking water standards in the United States. State and local health departments or environmental agencies work with municipal or public water authorities to meet the required primary standards. These water authorities must regularly test and, if necessary, treat their water to ensure that they are meeting the primary stand­ards. Individual or small private water systems (defined by the number of households connected to the water system) are not required to meet any water quality standards. However, owners of

private water systems are encouraged to use the EPA standards as benchmarks for testing and treatment of their water.

Health Canada (www. hc-sc. gc. ca) is the ministry responsible for drinking water standards in Canada and for educating Canadians about the importance of safe drinking water. The Guide­lines for Canadian Drinking Water Quality addresses many of the same primary and secondary contaminant issues as the EPA guidelines described earlier. Similar to the United States, Health Canada works with provincial and territorial governments to ensure that Canadian water is safe to drink as well as functional and aesthetic for household uses. Environment Canada (www. ec. gc. ca) monitors Canadian water quality and provides leadership for water management issues.

Primary Drinking Water Standards

The Primary Drinking Water Standards are based on the Maximum Contaminant Levels (MCLs), or highest concentration, of pollutants allowed in public drinking water. The pollutants that are regulated by the primary standards are those that are known to cause adverse health effects and for which there is information available about chronic or acute health risks. These pollutants in­clude: disease-causing organisms, such as bacteria; toxic chemicals, such as lead and nitrates; and radioactive contaminants, such as radon.

Secondary Drinking Water Standards

Secondary Drinking Water Standards are based on the Secondary Maximum Contaminant Levels (SMCLs) of pollutants that affect the aesthetics and function of water. These are contaminants that impact water qualities such as appearance, taste, odor, residues, or staining. Examples of second­ary standard contaminants are chloride, iron, manganese, sulfur, and altered pH. While these might not present a health threat, they can be very important to water use in the bathroom. Secondary standards are voluntary and are not required. A public water system may choose to test and treat for some of the SMCLs.