Nitrate is one of the state’s most widespread groundwater contaminants, according to research from the University of California, Davis, which reported that nitrate-contaminated groundwater poses public health risks for approximately 254,000 people living in two of the biggest agricultural areas of the state: the San Joaquin Valley’s Tulare Lake Basin and the Salinas Valley.
California set the drinking water standard for nitrate in 1962 and has regulated water quality since 1969.
The San Joaquin Valley is particularly hard hit by nitrate: 63 percent of the state’s public water systems that report violations of health standards for the contaminant in 2015 were in the Valley.
“Nitrate is the most critical, the most immediate contaminant in the San Joaquin Valley,” Harter says.
The San Joaquin Valley has three of the four California counties with the highest DBCP levels, which are triple that deemed to be safe by the state.
In 2015, 60 percent of the state’s public water systems reporting health violations for arsenic were in the Valley, and Madera County drinking water has the highest levels of arsenic statewide.
Without proper management, unlined pits can threaten groundwater quality, the Central Valley Regional Water Quality Control Board reports.
He only found out when he started working as policy director at the Community Water Center, which advocates for safe drinking water in the San Joaquin Valley, and he realized his town was one that had found the contaminant in its drinking water.
“But people lack safe drinking water in our own backyard.” Even when drinking water contains known toxins, it can be hard to prove that any single one affects people’s health.
“We don’t know how air pollution impacts the body differently from water pollution or how multiple effects work out,” Capitman says.