California’s $37.5 billion farming industry has led the nation in food production for more than 50 years. The state has known for decades that nitrate contamination has been a cost of that productivity. But now, state officials know the primary sources of contamination, just how extensive it is and who’s shouldering the burden.
Nitrates jeopardize the drinking water of 254,000 people out of the 2.6 million who rely on ground water in the Central Valley’s Tulare Lake Basin and Salinas Valley, according to a University of California, Davis study commissioned by the state Legislature and released in March. Agriculture accounts for 96 percent of that contamination.
The number of people exposed will likely grow. It can take decades for nitrates to travel from the soil surface to ground water.
“We know we can’t stop all sources tomorrow and that there will be a time lag until we get the situation under control,” said Thomas Harter, a ground water hydrologist who led the UC Davis study. “We will definitely see an increase in nitrate contamination over the next 10 or 20 years.”
Jessica Sanchez fills a glass from the tap and holds it up to the light. The water appears cloudy, almost opaque, as particles swirl around. After a few minutes, the particles settle, and the water looks normal.
That’s precisely the trouble, water activists say. You can’t see or taste nitrates. “If you have sulfur or manganese in your water, it looks brown and gross and you quit drinking it before it poisons you,” said Jennifer Clary, a policy analyst with Clean Water Action. “But with nitrates, you don’t.”
Nitrates become toxic when bacteria in saliva and the gut convert them to nitrites, which in turn convert hemoglobin into methemoglobin, which can’t deliver oxygen to tissues. Babies are vulnerable in part because their immature stomachs harbor abundant nitrite-producing bacteria.
Affected infants have trouble breathing and develop cyanosis, a blue-gray or purple tint to their skin, giving methemoglobinemia its common name, blue baby syndrome. Left untreated, babies develop brain damage, and eventually suffocate. Studies have linked high nitrate exposures in adults with miscarriage, digestive disorders, thyroid damage and cancer.
Health experts worry that people don’t know about the risks and that doctors may not consider nitrate exposure in their diagnoses.
Dr. Mark Miller used to treat patients in Chico, in the northern Central Valley, where some wells had nitrate levels 10 to 15 times higher than the federal standard. “But there was no awareness among clinicians and no effort from public health authorities to check wells and inform people about this hazard,” said Miller, director of the state’s Children’s Environmental Health Program and head of the University of California, San Francisco Pediatric Environmental Health Specialty Unit.
Doctors might see a newborn that was failing to thrive or had cyanosis and not even think to ask about nitrates, Miller said.
The majority of the at-risk residents get their water from public systems, many of which rely on a single well. East Orosi has two public wells and both regularly have unsafe nitrate levels. Managers of the town’s volunteer water board – the East Orosi Community Services District – did not respond to repeated requests for comment.
Sanchez went to Orosi High School, where administrators posted signs warning students not to drink the water. School officials dug a new well, only to find nitrates there, too.
For years, Dias, Sanchez’s mother, had to buy bottled water for her kids to take to school, on top of the water she bought for her home.