What element is primarily targeted by water quality criteria?

Water quality criteria primarily target contaminants that can significantly impact aquatic ecosystems and public health. Phosphorous is a key nutrient that can contribute to water quality issues, particularly through its role in algal blooms. When phosphorous levels are high, it can lead to eutrophication, where nutrient overload causes excessive growth of algae, depleting oxygen in the water and harming fish and other aquatic life.

Regulations often focus on managing phosphorous concentrations in surface waters to maintain ecological balance and prevent degradation of water quality. While nitrogen, carbon, and heavy metals like lead also have important environmental and health implications, phosphorous is often highlighted due to its specific and detrimental effects on aquatic systems, making it a significant focus in water quality management efforts.