California Association of Sanitation Agencies
Mercury is a naturally occurring element, exposure to which can affect the human nervous system, harm the brain, heart, kidneys and immune system.
If rinsed down the drain, the liquid metal will make its way to a wastewater treatment plant, which is not designed to remove toxic metals. As a result, some of that mercury will remain in the cleaned and disinfected wastewater that is discharged into receiving waters. That tiny amount of mercury would sink into the sediment. Bacteria and other natural processes would transform the mercury into methylmercury, which is easily absorbed by tiny plants and aquatic organisms in the water. From there, mercury begins its assent through the food chain.
Wastewater agencies throughout California are working to reduce the amount of mercury that enters the environment through a variety of programs: household hazardous waste collection facilities, installation of mercury amalgam separators in dental practices, and mercury thermometer exchanges in high school and college chemistry labs.