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.
Oxygen
Freshwater
| Range | Level | Impact |
|---|---|---|
| 6.5 – 9.5 mg/L | Met guideline | Threshold for supporting aquatic life, with 9.5mg/L needed to support early life stages |
| ≤ 6.5 mg/L | Exceeds chronic guideline | Low levels mean fish and invertebrates experience reduced growth, reproductive failure, and death |
Dissolved oxygen is the most fundamental parameter for aquatic life, and when levels drop too low fish and invertebrates experience reduced growth, reproductive failure, and death, with eggs and young organisms especially vulnerable. The U.S. EPA's 1986 Water Quality Criteria set coldwater standards at a 7-day mean of 9.5 mg/L for early life stages and 6.5 mg/L for other life stages, and warmwater standards at 6.0 mg/L and 5.5 mg/L respectively.
https://www.epa.gov/wqc/national-recommended-water-quality-criteria-aquatic-life-criteria-table