Environmental Monitoring

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Monitoring to date confirms that the coastal waters around Lahaina are safe for recreation and that concentrations of potentially harmful fire-related substances are well below levels of human health concern. Heavy rains can still carry storm (brown) water to coastal environments. Therefore, people continue to be advised not to enter coastal waters during Brown Water Advisory(ies). “Brown water” can contain harmful bacteria.

Water Quality Monitoring Efforts

DOH is reviewing the following sampling efforts:  

Concentration of Dissolved Fraction Over Time

Concentration of Total Fraction Over Time

Concentration of Conventional Parameters Over Time

In‑Situ Measurements

Figure 5. Interactive time series of in situ measurements collected during nearshore water quality sampling by DOH from April 2024 through February 2026. Water quality standards from HAR 11-54 are displayed for applicable analytes.

Surfrider Data

Surfrider conducted two rounds of sampling on West Maui after the fire. In January 2024, Surfrider collected grab samples for metals and PAH analysis during a post-fire “brown water” event after almost 4 inches of rainfall. In June 2024, Surfrider collected samples in accordance with DOH’s multi-incremental sampling protocols and analyzed them for fire-related metals. The June sampling was during the dry season and a south swell which could potentially re-suspend settled contaminants. Table 2 presents the most recent sampling results.

Understanding the Coastal Water Quality Data

The coastal waters around Lahaina are safe for ocean recreation. Sampling to date shows that fire-related substances are not present at levels of human health or ecological concern. 

Ongoing nearshore monitoring data show that the water chemistry (temperature, salinity, pH, and turbidity) has stayed relatively consistent before and after the fires. Based on the data reviewed, the measured parameters remain within the range of what has historically been observed at this site. While there have been periodic exceedances of certain nutrient parameters, current information does not indicate acute risks to human health or aquatic life. However, these exceedances may warrant continued monitoring to better understand any potential long‑term impacts.

Fire-related substances of primary interest include metals; water quality samples were analyzed for the same metals that were found at elevated levels in ash. DOH Environmental Action Levels (EALs) for marine habitats were used to compare sample results. The marine habitat EALs consider factors such as bioaccumulations (how substances build up in an organism) and aquatic habitat toxicity.  

No human health EALs have been developed for metals or other chemical substances for screening recreational waters. The World Health Organization (WHO) recommends a simple screening approach for exposures associated with recreational activities: screening values at 20 times established safe drinking water standards to account for the small amount of water that may be accidentally swallowed. Collectively, fire-related substances tested in nearshore waters fall below WHO screening levels. This conclusion is consistent with previous DOH news releases. 

Metals

The metals sampling results collected by both DOH and Surfrider are generally below the most stringent EALs for marine habitats and below HAR 11-54 screening values for acute and chronic scenarios for aquatic life. Slightly elevated levels of arsenic and silver are not expected to be harmful to human health. All reported metal levels (total and dissolved) are well below available WHO recreational water screening values (PDF, opens in a new tab).

Metal concentrations measured in nearshore coastal waters are not at levels beyond what might be normally expected. Volcanic soils on Maui have naturally high levels of metals in comparison to typical soils on the mainland United States, including aluminum, iron, manganese, and titanium. These naturally occurring metals could affect the levels of metals in sediment and nearshore coastal waters but are tightly bound to minerals in the soil and do not pose a health risk to residents or aquatic habitats. The Hawaiian Islands Soil Metal Background Evaluation Report – 2012 (PDF, opens in a new tab) includes information on background concentrations of metals in Hawaii sediments.

Polycyclic Aromatic Hydrocarbons (PAHs)

PAHs were detected at only two Surfrider sampling locations collected in January 2024 and at levels well below health-based screening levels. The sampling focus therefore remains on metals.

Air | Ash and Debris | Beach Sand | Coastal Sediment | Coastal Waters | County Parks | West Maui TDS Site | Soil