Much private well water in California’s Central Valley contains enough manganese to cause cognitive disabilities and motor control issues, according to a news release from the University of California – Riverside authored by Jules Bernstein.
A new study finds that, among Central Valley communities, the highest concentrations of manganese are in private well water systems. However, the researchers also found the metal in public water systems at higher concentrations than what studies have shown can have adverse health effects.
A naturally occurring metal, manganese is found in water supplies throughout the world. In the U.S. it is regulated only as a secondary contaminant, meaning no maximum level is enforced.
The study, published in the journal Environmental Science & Technology, not only measured levels of manganese in Central Valley water supplies but also mapped the highest concentration areas according to annual income levels.
Overall, the research team estimates nearly half of all domestic well water users in the Central Valley live in disadvantaged communities, as defined by annual income. Within this population, nearly 89% have a high likelihood of accessing water that is highly contaminated with manganese.
“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,” said Samantha Ying, UCR soil scientist and principal study investigator. “These people are particularly concentrated in disadvantaged communities, so if they wanted to monitor and treat the water, they would have a hard time doing so.”
Point-of-use treatment options range from oxidation and precipitation filters to water softeners, chlorination, and reverse osmosis systems.
But devices for monitoring water quality can cost up to $400 annually, and treatments for manganese-tainted water are just as expensive.
The researchers used a benchmark of 300 parts per billion of manganese to assess water quality. This is a level of manganese contamination that some studies have associated with neurological development issues, particularly for fetuses and infants during early growth periods. It is likely though that adverse effects can occur at lower levels.
“New studies from Canada, where manganese is now a primary contaminant, show there may be effects at 100 parts per billion,” Ying said. “We were being conservative at 300.”
This study focused on the Central Valley in part because the conditions that cause manganese to move from aquifer materials into water are so prevalent there. It is likely that drinking water from wells in other parts of the state is similarly tainted. Over 1.3 million Californians rely on unmonitored private wells.
