In January of 2006 United States Environmental Protection Agency dropped the MCL (maximum contaminant level) for arsenic in drinking water down to 10 ppb for arsenic from 50 ppb. By doing so, they caused many small and medium-sized public water systems to become out of compliance.
In order to get back into compliance, the majority of these systems installed expensive, complex filtration systems (reverse osmosis, etc.) and passed the cost of the equipment upgrades along to their customers. Smaller systems whose customer base could not afford such equipment upgrades sought financial assistance from the Federal Government.
