Potential impact of the 2023 Lahaina wildfire on the marine environment: Modeling the transport of ash-laden benzo[a]pyrene and pentachlorophenol

The Lahaina urban/wildland fire event is considered the deadliest wildfire in the past century of U.S. history. This fire resulted in over 2200 building structures destroyed or damaged, approximately 4000 automobiles were incinerated and between 450 and 878 ha of grassland burned in areas adjoining the town of Lahaina, Maui County, State of Hawaii, U.S.A. One of the most abundant contaminants of both wildland and urban fires is the incomplete combustion product, benzo[a]pyrene. Pentachlorophenol from burned and unburned utility poles/residential burn sites enter into navigable waters, thus posing a serious risk to the water quality of coastal waters. The Risk Quotient Plumes for benzo[a]pyrene and pentachlorophenol, mobilized from Lahaina into coastal waters were calculated based on a hydrodynamic analysis and an integrated ecological risk assessment. This plume was simulated using rainfall events in November 2022 as a proxy for the first major rainfall event expected in Lahaina in 2024. The models indicated that the estimated levels of benzo[a]pyrene and pentachlorophenol posed a risk to near shore habitants within 2 km of Lahaina. The levels of pentachlorophenol were more widespread than benzo[a]pyrene and were predicted to pose a hazard to marine life as far away as Molokini Shoal Marine Life Conservation District and 'Āhihi-Kīna'u Natural Area Reserve. Fisheries species captured near these areas should be tested for consumption safety.