What type of contaminants do secondary maximum contaminant levels (SMCLs) relate to?

Secondary maximum contaminant levels (SMCLs) are specifically established to address aesthetic concerns in drinking water rather than direct health effects. These contaminants can affect the taste, odor, and appearance of water, making it less palatable or visually appealing, but they are not considered to pose significant health risks. For instance, SMCLs might include substances like iron or manganese, which, while not harmful at typical levels, can lead to discoloration or staining of laundry and fixtures. Understanding the distinction between primary contaminants, which directly impact human health, and secondary contaminants, which primarily concern consumer acceptance, is vital for water quality management and ensuring safe drinking water.