We've made some changes to EPA.gov. If the information you are looking for is not here, you may be able to find it on the EPA Web Archive or the January 19, 2017 Web Snapshot.

EPA's website will operate in a diminished capacity on Saturday Feb 17, 2018 from 8:00 a.m. to noon EST for routine maintenance. Some services, such as search, may be temporarily unavailable for brief periods during this time. We apologize for any inconvenience.

Basic Information on Water Quality Criteria

EPA develops criteria for determining when water has become unsafe for people and wildlife using the latest scientific knowledge. These criteria are recommendations. State and tribal governments may use these criteria or use them as guidance in developing their own.

Section 304 (a) (1) of the Clean Water Act (PDF) (6 pp, 153 K, About PDF) directs EPA to develop these criteria.

On this page:

Aquatic Life Criteria

EPA bases aquatic life criteria on how much of a chemical can be present in surface water before it is likely to harm plant and animal life. EPA designs aquatic life criteria to protect both freshwater and saltwater organisms from short-term and long-term exposure.

Biological Criteria

Biological criteria are indications of how healthy water bodies based on how many and what kinds of organisms are present.

Human Health Criteria

Pollutants can harm people’s health when they drink water or eat seafood from contaminated surface water. EPA scientists research how much of a specific chemical can be present in surface water before it is likely to harm human health. Based on this research, EPA develops human health criteria.

Microbial/Recreational Criteria

Bacteria and other pathogens can make our waters unsafe for humans.  EPA develops microbial criteria to determine when water is safe for recreational activities such as swimming.

Suspended and Bedded Sediment Criteria Guidance

Organisms such as worms and plants often live in the sediment at the bottom of rivers, lakes and other water bodies. Pollutants in sediment can make their way up the food chain and threaten larger animals as well as people. For this reason, EPA has developed guidance on developing criteria for suspended and bedded sediment.

Top of Page