THE DAILY MAIL - More than 1.3 million Californians may be drinking high levels of manganese, enough to cause cognitive disabilities in children and Parkinson's-like symptoms in adults.
The discovery was made by researchers at the University of California - Riverside (UCR), who discovered the mineral is thriving in untreated wells throughout Central Valley.
The study inspected private wells and public water systems - with nearly half of the affected residents living in disadvantaged communities - and found that almost 89 percent are likely to access water highly contaminated with manganese.
Samantha Ying, UCR soil scientist and principal study investigator, said in a statement: 'It is a relatively small number of people, compared to the total population of the state, who are getting the tainted water.
'But for them, the health risks are high.'