MBAS are foaming agents from detergents and cleaning products. They cause water to foam and can affect taste and appearance. Common in household wastewater.

MBAS (Methylene Blue Active Substances) is a method used to measure anionic surfactants in water, primarily from detergents and cleaning products. These substances enter water systems through household and industrial wastewater discharge. While not typically harmful at low levels, high concentrations can cause excessive foaming, alter water taste, and create aesthetic issues. The MBAS test involves a reaction with methylene blue dye to quantify surfactant levels. Environmental concerns include potential impacts on aquatic ecosystems.