Credit: Hawaii Wing Civil Air Patrol.
The 2023 wildfire in Lahaina, Hawaii, is considered the deadliest wildfire in the U.S. in the past century. One hundred and two people were killed, thousands of buildings and automobiles were incinerated, and as many as 2,170 acres of grassland burned.
A multi-institutional research team led by the Haereticus Environmental Laboratory modeled where stormwater might carry ash from the fire to determine which fisheries and coral reefs around Maui might be at risk of contamination. The researchers used data from past rainfall events to simulate potential plumes of two toxic chemicals associated with urban and wildland fires: benzo[a]pyrene and pentachlorophenol. These theoretical loading calculations are best-effort estimates that are not actual measured amounts.
Benzo[a]pyrene is a combustion product of burned wood, grass, plastics, tires, and petroleum-based fuels and can be carcinogenic and neurotoxic. Pentachlorophenol is an industrial wood preservative used mainly to treat utility poles. Over 690 utility poles in the Lahaina area were damaged by the fire, with about half needing replacement due to irreparable damage. Given its documented toxicity and the emergence of viable alternatives, the U.S. Environmental Protection Agency banned pentachlorophenol earlier this year.
Both chemicals bioaccumulate and biomagnify in the marine food web, placing fishers and seafood consumers at possible risk of exposure and disease. The chemicals can also cause reproductive failure in fish and make corals more susceptible to bleaching, whereby corals lose the symbiotic algae in their tissues that they need to survive.
The theoretical model indicated that the estimated levels of benzo[a]pyrene and pentachlorophenol posed the greatest risk to nearshore marine life and habitats within 1.25 miles of Lahaina. The levels of pentachlorophenol were more widespread than benzo[a]pyrene and were predicted to reach coral reefs as far away as those around Molokini Crater, 20 miles south of Lahaina.
Hydrodynamic plume modeling of runoff that incorporates a risk quotient component can help guide local fish and shellfish monitoring efforts and inform related seafood consumption warnings.
