Surfactants, or surface-active agents, are chemicals that reduce the surface tension of oil and water. In detergents, surfactants would help dirt to drop out and stay out of clothing or other items being cleaned, although because of the thickening properties in detergents, this does not occur. Instead, fabrics may be filled with toxic residue.
Surfactants in detergents are toxic to aquatic life, persist in the environment and break down into additional toxic byproducts, according to the U.S. Environmental Protection Agency.
In a freshwater environment, surfactant-containing detergents break down the protective mucus layer that coats fish, protecting them from parasites and bacteria, according to Lenntech. The reduced surface tension of water also makes it easier for aquatic life to absorb pesticides, phenols and other pollutants in the water. The EPA also advises that surfactants can disrupt the endocrine systems of humans and animals; Lenntech notes that surfactants decrease the breeding rates of aquatic organisms.