Which agency sets standards on the concentration levels of harmful contaminants in drinking water?

The Environmental Protection Agency (EPA) is the agency responsible for establishing and enforcing regulations concerning the concentration levels of harmful contaminants in drinking water in the United States. This responsibility is part of the EPA's mission to protect public health and the environment.

The EPA sets standards for water quality under the Safe Drinking Water Act, which includes limits on specific contaminants that can be present in public drinking water supplies. These standards are based on scientific research and assessments of health risks to ensure that the water supplied to the public is safe for consumption.

While other organizations, such as the World Health Organization (WHO), provide guidelines and recommendations on drinking water quality, the EPA has the regulatory authority to enforce compliance within the United States. The CDC focuses primarily on public health and disease control, while the National Institutes of Health (NIH) conducts medical research but does not regulate water quality standards.