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Months of water sampling along Lahaina’s burned coastline have turned up surprisingly clean results, allaying concerns that fire-related pollution from last summer’s urban inferno might have found its way into nearshore waters.

A research team from the University of Hawaii had found concerning levels of copper and zinc at the Lahaina harbor in early October samples, but the heavy metals’ concentration dissipated over time and the levels were only considered toxic for aquatic species, not humans.

The researchers have not found any highly toxic polychlorinated biphenyls, also known as PCBs, in the sampling. But they did detect very low levels of three other organic contaminants: , and

“What we’re seeing is a lot better than we expected,” said lead researcher Andrea Kealoha in an interview Tuesday.

She cautioned that the results are preliminary, data analysis is ongoing and long-term monitoring is needed.

Kealoha, now an assistant professor with the University of Hawaii School of Ocean and Earth Science and Technology, was born, raised and lives on Maui.

“The love for my community and culture is the motivation for all of my research,” she said. “I want to make sure that the work we do in Lahaina and throughout Hawaii is guided by our community and responds to the needs of our communities.”

Joining her on the team were UH researchers , and and a number of their students.

The team assembled quickly after the Aug. 8 wildfire that killed at least 101 people, destroyed more than 2,200 structures and wiped out most of the historic community.

With $200,000 from the , researchers, students and collaborators began collecting samples on Oct. 8 at nine sites along the coast of Lahaina and at two control sites to the north and south of the 5-mile burn zone.

During five rounds of sampling that continued until February, they tested for nutrients, metals, organic contaminants, carbonate chemistry, microbial community and coral stress metabolites.

In addition to shoreline sampling, they also used small boats to collect samples and deployed sensors in Wahikuli, Kahoma Stream, Baby Beach, Lahaina Harbor and Puamana with control sites in Kahekili to the north of town and Olowalu to the south.

The scientists wanted to find out what’s in the water, if it is dangerous to eat locally caught fish, what impact the fire had on coral reefs, and how the marine ecosystem’s future resilience might be affected.

Some answers will take time to emerge. Nalley, a researcher with Hawaii Sea Grant, for example, is testing fish samples and isn’t expected to have results for several months.

UH graduate student Sean Swift is analyzing 126 different organic contaminants and his results will take two to three months before they will be publicly available, Kealoha said.

Besides PCBs, the list of contaminants he’s tracking includes pesticides and polycyclic aromatic hydrocarbons, often associated with gasoline, other petroleum products and coal. They can be released from wood and cigarette smoke or other sources.

Samples taken from Wahikuli and Mala Wharf that Swift has analyzed so far show low levels of phenol, naphthalene and benzyl alcohol, according to Kealoha, who gave a on March 11 for .

The elevated copper and zinc levels found at the Lahaina harbor and ferry pier likely stem from antifouling paint boaters use to coat their hulls. The paint prevents barnacles, algae and other organic materials from attaching but it can into the environment, Hawco said in an interview.

The copper results from early October approached if not exceeded set by the U.S. Environmental Protection Agency marking chronic or acute toxicity for aquatic life, he said. Those results were found both at the harbor and pier.

To some extent, the copper results were no surprise to scientists.

“We expect to see higher concentrations of copper in harbors because of boats and antifouling paint,” Kealoha said.

By November the high copper levels had dropped by about 40% and by January they were below EPA threshold levels, according to Hawco.  

What’s not clear at this point is if the copper and zinc residue has sunk to the ocean floor or whether wave and tidal action has washed it out to sea, Hawco said.

Further monitoring is needed to determine that, and the research team hopes to secure additional funding to make it a long-term project.

Knowing where the copper and zinc went will be especially important if and when government officials decide to dredge the harbor, Hawco said. If the ocean floor is contaminated with heavy metals, it might not be wise to stir it up with a dredging project. Or if dredging is to occur, knowing what’s on the bottom first would be prudent before any work begins.

One surprising finding is that elevated levels of arsenic were not detected, Hawco said, given how many Lahaina buildings were built decades ago when construction materials such as were used.

Canec is a fiberboard building material manufactured in Hawaii in the early 1930s to the early 1960s from residential sugar cane fiber. Often used in ceilings and walls, Canec was treated with inorganic arsenic compounds to control termites.

Daily exposure to very high levels of inorganic arsenic over many years can result in various health effects, including increased cancer risk, according to the Hawaii Department of Health.

Kealoha’s work, which focuses on studying the fires’ impact on the coral reefs, will continue. The chemical oceanographer is digging into how well the reefs are breathing and growing through processes involving photosynthesis and calcification.

One thing that stresses coral reefs is nitrates, which are associated with fertilizers and wastewater. Water samples taken after a large storm event in January produced some concerning levels of nitrates but that’s to be expected, Kealoha said.

But there’s no strong evidence that runoff from the burn zone is creating a pathway for nitrates to flow into the seawater, she said.

With ocean temperatures warming and becoming more acidic because of climate change, and with heavy use by snorkelers, swimmers and other ocean users, Hawaii’s coral reefs are confronting major stressors.

Any additional stress from fire-related impacts, including reduced water quality, enhanced nutrients and turbidity and low oxygen, need to be closely watched going forward, Kealoha said.

One thing Lahaina’s reef complex has going for it right now is that because tourism numbers are down compared to normal levels, the reef is getting a bit of a breather, much like it did during the pandemic.

“When these reefs get a break, they recover,” Kealoha said.

The university team is collaborating with various partners on this ongoing research. The partners include the state, , the , , , and community members.

Civil Beat’s coverage of environmental issues on Maui is supported by grants from the Center for Disaster Philanthropy and the Hawaii Wildfires Recovery Fund, the Knight Foundation and the Doris Duke Foundation.  

Civil Beat’s coverage of Maui County is supported in part by a grant from the Nuestro Futuro Foundation.

Civil Beat’s community health coverage is supported by the Swayne Family Fund of Hawaii Community Foundation, the Cooke Foundation, and Papa Ola Lokahi.