The East Bay Municipal Utility District, or EBMUD, recently reported a decrease in trihalomethane — a disinfection byproduct that forms after chlorine reacts with organic material in the water and has been linked to cancer — in its drinking water after new operational adjustments, according to a EBMUD press release issued Friday.

Tests conducted by the district in July at 16 tap locations revealed that trihalomethane, or THM, concentration ranged between 30-57 parts per billion (ppb), well below the 80 ppb federal Maximum Contamination Level, according to EBMUD spokesperson Jenesse Miller. The district purposefully selects at-risk locations, such as taps at the end of a water system line, that will record higher than system averages.

“We started noticing (THM) levels creeping up over the last two years,” Miller said. “This spike led to an all-hands-on-deck approach.”

EBMUD found that a testing location tap in the Berkeley Hills was above 80 ppb and an Orinda tap was near the maximum last April, according to Miller. Miller said the heavy rain after California’s “prolonged drought” washed an unprecedented amount of organic matter into the source water, which began to decay and interact with the chlorine in treated water.

In the wake of these locational THM spikes, EBMUD assembled 15 in-house water quality experts to help address the problem in June about the April levels. The district has also increased its testing, examined “at what point in the process can we apply chlorination to the water” and instituted new pilot programs, such as the piloting of a new aeration system at the Lafayette plant that blows THMs out of the water in a controlled setting, according to Miller.

“It’s a challenge to chlorinate for disinfection while minimizing the compounds that form as byproduct,” explained campus public health lecturer Charlotte Smith. “There are a lot of ways to solve the issue, but there are a lot of moving parts.”

EBMUD also has several long-term goals for quelling THM concentration, including reducing water age and converting open cut reservoirs to smaller more manageable sizes, Miller said. The district is also considering adding or upgrading the ozonation process at some water plants, in which ozone is used instead of chlorine, to disinfect water.

City Councilmember Kriss Worthington said the THM levels detected over the past quarters have all been significantly under unhealthy levels. He considered the THM spikes a “small worry,” but said that EBMUD is now “headed in the right direction.”

According to Smith, long term exposure to THM’s has been linked to bladder cancer. Ingesting THMs have proven to be the most dangerous. The federal maximum levels, however, are conservative. An average Brita filter can also filter out any residual THMs, Smith said.

“I’m happy they’re improving the water,” said longtime Berkeley resident and campus alumna Shannon Nicholls. “But… I still don’t trust (EBMUD).”

“EBMUD and many other California water districts will continue to struggle with THM concentrations,” Miller said. “We’re not at the point where we can claim victory.”