American Canyon residents are being notified that earlier this year, city drinking water contained elevated levels of a chemical associated with miscarriages and other health problems.
Trihalomethane, or THM, is a colorless, odorless chemical that was detected at levels nearly twice what the Environmental Protection Agency says is safe for human consumption. Samples taken from March to June from all four monitoring sites in the city exceeded safety standards.
The drinking water is now back to normal THM levels, according to Robert Weil, director of the American Canyon public works department. Weil downplayed the problem, and pointed out that in the past water samples showed similar spikes in THM levels, though never enough to trigger a public notice.
There is also a difference of opinion regarding the risk posed by THM. City officials have said only long-term exposure to the chemical can cause risk.
Brian Smith, a federal EPA official, said studies have linked short-term exposure to THM with miscarriages. Studies also link long-term exposure with liver, kidney and central nervous system problems and increased cancer risk, Smith said.
"We're telling people to get informed and if they have concerns, to contact their doctor," Weil said.
THM forms when dissolved organic compounds, such as decomposing plant material or pesticides, react with the chlorine used during water treatment, according to the EPA.
Weil attributed the problem to the heavy rainfall this winter and spring, which put increased amounts of green waste into the water. This and improper treatment at the city's new water plant -- which just came online in December -- caused the problem, he said. He added that officials have since adjusted pH levels during treatment, which returned THM levels to a normal range.
American Canyon, like Napa, receives its water from the North Bay aqueduct, which pulls water from the Sacramento River Delta. But Napa also uses water from Lake Hennessey and may be able to dilute out high levels of THM or treat it out, as American Canyon is now doing, Weil said.
Napa officials were not available for comment.
In 2002, the EPA changed its risk assessment of THM, lowering the allowable amount of THM in drinking water from 100 parts per billion to 80 parts per billion. American Canyon averaged 95 parts per billion over the last year.
The highest spike occurred in March, when water samples contained THM at levels ranging from 140 to 155 parts per billion. A similar spike occurred in March of 2003, Weil said, but because THM levels in the previous quarter were low, residents were not notified.
The California Department of Health monitors THM levels and requires cities to notify their residents if the running yearly average exceeds EPA safety standards. Samples are taken quarterly.
Although American Canyon's samples have shown high THM levels in the past, low levels in preceding quarters always pulled the yearly average down to normal range, Weil said.
Weil said city officials learned about the elevated THM levels in late July, but waited to notify residents until they had received direction from the California Department of Health Services.
A notice to boil water was never issued because this is ineffective treatment for THM, Weil said. He added that Karen Smith, Napa County health officer, was notified two weeks ago, but has not responded. Smith did not return phone calls for this article.
American Canyon Mayor Cecil Shaver said he had no plans to change policy in notifying residents. "It wasn't explained to me as being that critical," he said.
Because of the high levels between March and June, Weil said that the yearly average may not be down by the next quarter, either. If so, American Canyon residents will receive another notice in a few months that the yearly average of THM in their water exceeds EPA safety guidelines, Weil said.
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On the Net:
http://www.epa.gov/dclead/disinfection.htm
http://www.ehib.org
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