What is the Secondary MCL for Manganese?

The Secondary Maximum Contaminant Level (MCL) for manganese is established primarily due to aesthetic considerations, such as taste or staining, rather than health effects. Manganese is often found in water supplies, and while it is essential in small amounts for human nutrition, excessive concentrations can lead to undesirable effects.

A value of 0.05 ppm (parts per million) reflects the level at which manganese may start to pose aesthetic concerns—such as discoloration or staining of plumbing fixtures and laundry—without posing a direct health risk. Therefore, maintaining manganese levels at or below this threshold helps to ensure that water remains palatable and does not lead to other secondary issues for consumers. This standard serves as a guideline to protect both health and the integrity of water delivery systems.