Two public drinking water wells in Costa Mesa and Huntington Beach have been shut down because a suspected cancer-causing chemical was unknowingly injected into the local water supply, Orange County Water District officials said Wednesday.
NDMA, or n-nitrosodimethylamine, is a ubiquitous chemical that occurs naturally, but also is a byproduct of chlorinating water supplies to disinfect them. It is found in rocket fuel, pesticides, lubricants, cosmetics and all kinds of food, from bacon to beer and at far higher levels than turned up in local water tests.
However, with the state beginning to regulate the chemical, water district officials shut down the wells that exceeded state limits and are exploring ways to eliminate its presence.
The affected wells delivered water from the aquifer to those cities. There is believed to be no threat to public health, district officials said.
“Based on testing to date and dilution at drinking water wells, [the water district] believes Orange County’s ground water is safe,” said William R. Mills, Jr., general manager of the water district.
NDMA as yet is not regulated by federal or state authorities. But the state Department of Health Services recently issued temporary guidelines requiring action if concentrations in drinking water exceed 20 parts per trillion. That level of exposure is expected to cause one extra cancer case per million residents who consume two liters of water per day for 70 years.
The water district first discovered the presence of the chemical last year, when it was testing its underground aquifer for pesticides and herbicides. At the water district’s 200 wells, all met state guidelines in 1999. But last week, tests at the two wells showed concentrations of 32 to 35 parts per trillion.
The chemical can be traced to chlorinated waste water used by the district as a barrier to keep seawater from reaching underground aquifers. Chlorine, a common disinfectant used to purify water and kill pathogens, stimulates the chemical reaction that creates NDMA. In late 1999, water in the seawater intrusion barrier itself averaged 185 parts of NDMA per trillion, just shy of the state’s threshold that would result in mandatory shutdown of the barrier, said Michael P. Wehner, associate general manager for water science and technology at the water district.
Levels at nearby monitoring stations were as high as 150 parts per trillion near the seawater intrusion barrier. However, Mills said the chemical was diluted as it passed through the aquifer.
Karl Kemp, general manager of Mesa Consolidated Water District, which operates one of the wells, said his agency is continuing to test the water and also is exploring ultraviolet devices to destroy the carcinogen.
It’s unknown how long the water supply has been contaminated with NDMA. Technology that measures such minute particles only became available recently. The chemical was first found in water in 1998 at an aerospace facility near Sacramento. It was subsequently found in the San Gabriel Valley ground-water basin. The problem is probably more widespread; however, California is leading the nation in monitoring and reducing it. The state Department of Health is conducting a statewide study to see how widespread the problem is.
“There hasn’t been much looking in other parts of the country,” Wehner said.
The water district has formed a task force with the Orange County Sanitation District, the provider of the waste water. The agencies are exploring methods to treat and eliminate the compounds that form NDMA, such as nitrites.
“The best solution is to find the source,” Mills said. “That will take longer.”
These findings should not eliminate the use of chlorine as a disinfectant, said Robert Hultquist, chief of the drinking water technical operations section of the state health department.
“Chlorine is the most effective way to control [disease-causing] microorganisms, such as bacteria, virus, parasites,” he said. “Chlorine eliminates that risk. This is an extremely helpful chemical.”
Officials must balance the risks, he said.
“If we had un-disinfected water, one out of 1,000 people would get sick every year with potentially life-threatening illnesses,” Hultquist said.
However, environmentalists said this discovery reinforces the unknowns of chlorine disinfection.
“Chlorine clearly over the last century has been good for public health,” said Erik Olson, head of drinking water programs at the Natural Resources Defense Council’s office in Washington. “The one problem is there is a dark side to the use of chlorine that we’ve only really begun to learn about in the last 10 years.”
Hundreds of byproducts are created when chlorine is used to disinfect water, Olson said, and more than half remain unknown.
“It is now becoming clear that when you chlorinate drinking water, you create a toxic alphabet soup of chemicals that can cause cancer and [possibly] miscarriages and birth defects,” he said, referring to a 1998 study that linked increased risk of miscarriage with trihalomethanes, a chemical common in chlorinated drinking water.
“That’s the bad news. The good news is we now have the technology that we can take right off the shelf to largely eliminate the problems.”
There are alternatives such as carbon-filtration or using ozone or ultraviolet light in place of the chlorine as a primary disinfectant, he said.
These “were not available 20 to 30 years ago,” Olson said.
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Water vs. Water
To prevent ocean water from mixing underground with the drinking water aquifer, the Orange County Water District injects a barrier of pressurized chlorinated water. A carcinogen associated with chlorinated water, NDMA, has gotten into the drinking water supply -- forcing the closure of two wells.
Graphics reporting by BRADY MacDONALD / Los Angeles Times