Contaminants exist in water supplies from both natural and manmade sources. Even those chemicals present without human intervention can be mobilized from introduction of certain pollutants from both point and nonpoint sources.  

Water Contaminant Standards

The California Office of Environmental Health Hazard Assessment’s (OEHHA) Public Heath Goals (PHGs) provide ideal standards for amounts of various chemicals in drinking water. PHGs are based on researched health effects that could be caused by excess concentrations of these chemicals, and a comprehensive list of PHGs is available to the public.

It is the legal responsibility of the State Water Resources Control Board (State Water Board) to ensure the actual levels are as close as possible to these objectives while accounting for practical, financial or scientific limitations. 

The U.S. Environmental Protection Agency (EPA) sets national obligatory standards for various chemicals called Maximum Contaminant Levels (MCLs). The State Water Board supplemented these national regulations with “notification levels,” which are standards for chemicals not specified by the EPA.

Some of California water’s most prolific contaminants include arsenic, coliform bacteria, pesticides, disinfectant byproducts, uranium and nitrates, of which the latter are found in the highest concentrations. 

California’s San Joaquin Valley exceeds MCLs more than anywhere else and is home to some of the most polluted aquifers in the US, causing a plethora of health, environmental, social and economic consequences.