It is estimated that dental amalgam contributes to over half of the mercury waste entering POTWs (Publicly Owned Treatment Works). When a separator is not used and amalgam fillings are drilled, the amalgam waste that is produced is flushed with wastewater into the sewer systems. Traces of mercury contained within the amalgam can then leach into groundwater and into the environment. Typically it settles in the aquatic ecosystem, where it accumulates in high concentrations, and eventually contaminates plants and animals faster than it can be naturally reduced. Over time, animals farther up the food chain inevitably consume contaminated plants and smaller animals resulting in a process known as mercury biomagnification, in which the concentrations of mercury increase significantly.