The maximum permissible concentration of an inorganic chemical or other contaminant that the EPA will allow in water supplied to any user of a public water system before declaring it unsafe for human consumption.
"California is the first and only state in the nation to establish a maximum contaminant level specifically for chromium-6 in drinking water," said Ron Chapman, MD, MPH, director of the California Department of Public Health in a statement.
Unlike a PWS, where a violation of the maximum contaminant level directly affects the citizen's tap water, the connection between injection of illegal contaminant levels into the ground and pollution of tap water could be more tenuous.
One sample contained tetrachloroethene at nine times greater than the WHO guidance values for exposure limits and 70 times the US Environmental Protection Agency maximum contaminant level for drinking water.
In January, the allowed maximum contaminant level for arsenic in drinking water was lowered by the US Environmental Protection Agency (EPA) from 50 to 10 parts per billion (ppb), bringing the American regulation in line with standards already promulgated by the European Union and the World Health Organization.
* Less than 1% of all drinking water systems would be affected if a maximum contaminant level (MCL) of 20 [micro]g/L were established for perchlorate; that would rise to 4% if the MCL were set lower at 2 [micro]g/L.
The bill calls for a study by the National Academy of Sciences (NAS) to determine an "appropriate maximum contaminant level goal for chromium 6," a substance used as a rust inhibitor and in paint pigment.
The new standards for disinfection by-products will require improved treatment practices and a new Maximum Contaminant Level (MCL), i.e., reductions in the amount of by-products allowable in finished drinking water.