United States
About this guideline ▾
The United States has two sets of federal water quality guidelines. The EPA Aquatic Life Criteria set recommended concentration limits for pollutants to protect aquatic species under the Clean Water Act. The EPA 2012 Recreational Water Quality Criteria provide thresholds to protect human health in freshwater and coastal waters used for swimming and other primary contact recreation.
pH
Freshwater
| Low | High | Level | Impact |
|---|---|---|---|
| 6.5 – 9.0 | Met guideline | Within range that protects aquatic life | |
| 0.0 – 6.5 | 9.0 – 14.0 | Exceeds chronic guideline | Outside of range that protects aquatic life |
pH measures how acidic or alkaline water is, and it affects the toxicity of many substances in the water as well as the ability of fish and invertebrates to breathe, reproduce, and survive. Outside the acceptable range, fish experience increasing physiological stress, and sensitive invertebrates like mayflies can be affected at levels that seem only mildly acidic. The U.S. EPA's 1986 Water Quality Criteria recommend a freshwater pH range of 6.5 to 9.0 to protect aquatic life.
https://www.epa.gov/wqc/national-recommended-water-quality-criteria-aquatic-life-criteria-table