What We Monitor

Maui Wildfire Data: What We Monitor

DOH and partners collect samples and test them for substances such as heavy metals (like lead, arsenic, cobalt, copper, and zinc), asbestos, polycyclic aromatic hydrocarbons (PAHs), dioxins, and other hazardous substances that could have been released during the fires in Lahaina and Kula. DOH also monitors whether windblown dust and stormwater runoff are still spreading fire-related substances in the environment around Lahaina. When tests detect a substance at a level of concern, DOH looks at many samples collected over time to determine whether the substance level is elevated because of the fires, for another reason, or because it occurs naturally in the area. DOH also modifies the list of substances for analysis based on initial sampling activities to focus on substances at levels of concern. As of June 2024, monitoring activities include:

Sampling ash from burned homes in Lahaina and Kula and testing them for heavy metals, dioxins, PAHs, asbestos, and other substances of potential concern. (Visit the Ash page for more information and results.)
Monitoring air quality with more than 50 devices mounted throughout Lahaina that continuously measure levels of particle pollution in the air. DOH also tests particles from the air to see if they contain metals or asbestos fibers. (Visit the Air page for more information and results.)

Sampling coastal water, with samples collected by four different organizations quarterly to weekly. Samples are tested for metals (the primary substances of concern, based on ash sampling), nutrients, and other aspects of water quality. This sampling is important because hurricane-force winds during the fire blew smoke and ash far offshore, and because stormwater runoff could continue to carry fire-related substances into coastal waters. (Visit the Nearshore Coastal Water Quality page for more information and results.)
Quarterly sampling of sediment at nine locations along the coast, starting in May 2024. Samples collected to date, including from many other locations on and near shore, have been tested for up to 85 different substances of potential concern, including metals. (Visit the Sediment page for more information and results.)
Beach sand sampling for metals at three beaches near the burn area. (Visit the Beach Sand page for more information and results.)
Testing of air, groundwater, and runoff (leachate) at the West Maui Temporary Debris Storage (TDS) Site near Olowalu, along with portable air monitoring during debris removal activities in Lahaina. (Visit the TDS Site page for more information and results.)

The conceptual site model below shows how these monitoring activities cover the many ways in which people could come into contact with potentially hazardous substances from the fires. As recovery continues, results from ongoing monitoring will allow DOH to make decisions that keep people safe. Providing the results of the ongoing monitoring through this portal will also empower the people of Lahaina and Kula to make their own informed decisions.

Conceptual Site Model

This Conceptual Site Model shows how fire-related substances could move through the environment, how people are possibly exposed, and how sampling and monitoring programs have been set up to assess the potential for exposure and inform people about potential exposures.

Monitoring focuses on three potential “exposure pathways.” These pathways are based on our understanding of how fire-related substances could move through the environment and how people could come into contact with them. The pathways are numbered in the diagram above as follows:

1. Air

Residents, visitors, and workers could breathe in particulates from the air. Measures are in place to stabilize ash and dust (Soiltac®) and suppress dust during removal activities. Multiple air monitors are continuously active and consistently show good quality air.

2. Settled Debris and Ash

Disturbed ash and debris could lead to skin contact and incidental ingestion. Safety measures protect workers during removal activities. Before allowing public access or issuing completion letters for rebuilding, samples are collected to confirm fire-related substance levels are below levels of public health concern.

3. Nearshore Water and Sediment

People could contact ash in water and sediment during recreation, especially after rain. Continued sampling shows that fire-related substance levels are below levels of public health concern, even on Brown Water Advisory days.

Table 1 provides a more detailed discussion of the conceptual site model. It identifies specific receptors (people who could be exposed to fire-related substances originating from remaining ash and debris), how and when they might be exposed, and steps that DOH and partners are taking to monitor and prevent these possible exposures. DOH looks at the actual concentrations of substances in the environment and compares them with established screening levels such as DOH’s Environmental Action Levels. The appropriate screening levels depend on factors such as the exposure route and length of exposure. Based on the wide range of sampling conducted so far, heavy metals appear to be the fire-related substances that pose the highest concern in the environment around Lahaina. One possible explanation for this result is that this particular fire was so intensely hot that it could have destroyed other substances that might typically be found after a fire. Widespread evidence of melted glass, aluminum, and even asbestos means the fire was hot enough to destroy most dioxins and PAHs, for example.

These findings mean that metals are the main risk drivers in the area. In other words, out of all the substances that could have been produced by the fire, metals likely pose the greatest risk to people and ecosystems. Therefore, ongoing sampling activities continue to focus on metals. If a particular sample reveals highly elevated concentrations of metals, it likely indicates a high concentration of ash in that area. DOH can then test that area for additional substances of concern.

Table 2 shows additional ways that fire-related substances could move through the environment, and explains why people are not expected to come into direct contact with substances through these routes. For example, some substances on land can eventually leach into groundwater, but people do not contact the leachate or use the groundwater under Lahaina for drinking water. This means the pathway is “incomplete.” Although these exposures do not currently occur, DOH will consider whether any changes in site conditions might warrant DOH and partners to reevaluate them.

Table 1. Potential exposure pathways.

Exposure Points	Exposure Type (Route)	Receptors	Timeframe	Explanatory Notes
Settled/stabilized ash and debris	Direct contact (dermal, incidental ingestion)	Debris removal workers	Current	Safety measures are in place to protect workers during removal activities.
Settled/stabilized ash and debris	Direct contact (dermal, incidental ingestion)	Area residents, visitors, other workers	Current/future	The potential exists for people to disturb settled/stabilized ash. Before allowing public access or issuing completion letters for rebuilding, samples are collected to confirm fire-related COPCs are below levels of public health concern.
Air	Inhalation of released particulates	Area residents, visitors, workers	Current/future	Beginning in September 2023, the U.S. Environmental Protection Agency (EPA) sprayed Soiltac® on the ash to keep it in place and to reduce the chance of people breathing or ingesting ash and prevent it from spreading through the environment. Continuous particulate air monitoring is conducted at multiple locations in Lahaina and Olowalu. Air samples are also being analyzed in a laboratory for metals and asbestos. During all debris removal activities, dust suppression measures are required as well as air monitoring to confirm dust levels are being controlled. Data from this monitoring reveals consistently good air.
Nearshore coastal waters and sediments	Direct contact (dermal, incidental ingestion)	Recreational users	Current/future	Following large rainfall events, fire-related COPCs may be carried to the ocean. Limited exposure potential exists because DOH issues Brown Water Advisories on these days. Surface water and sediment sampling is ongoing. Based on samples collected to date, no fire-related COPCs are present in nearshore waters and sediment at levels of human health concern, even on Brown Water Advisory days.
Food chain	Fish ingestion	Local fishers	Current/future	Monitoring shows that levels of fire-related COPCs (metals) in nearshore water and sediment are at background levels and are not expected to be elevated in fish. Metals introduced into the environment from the wildfires would not yet have bioaccumulated in fish.

COPC = Fire-related contaminant of potential concern
DOH = Hawaii Department of Health

Table 2. Eliminated exposure pathways.

Eliminated Exposure Points	Eliminated Exposure Routes	Reason for Eliminating Exposure Pathway
Food chain	Shellfish ingestion	Shellfish are not generally present and there is no evidence of shellfish harvesting for consumption in nearshore waters in Lahaina.
Food chain	Fruit and vegetable consumption	The wildfire destroyed most vegetation in the Lahaina area, greatly limiting any exposures that may occur in the near term due to ingestion of fruits and vegetables. Properties are being cleared and scraped with sampling to ensure that fire-related COPCs are not above DOH and site-specific screening levels before public access or rebuilding is allowed and so plants with shallow root systems may be planted and safely consumed. Fruit trees have roots deeper than the depth of ash. Sampling after ash removal to date confirms that no fire-related COPCs are present at levels of concern in root zones for any remaining fruit trees.
Inland surface water and sediments	Incidental contact	Residents do not use surface waters in the ditches and streams in Lahaina for recreational or other purposes, thus eliminating any potential contact.
Groundwater	Ingestion	Leaching from the surface and discharge into marine waters is possible, but the Soiltac® applied by EPA reduces leaching potential. Groundwater is not used for drinking water.
Public drinking water	Ingestion	All areas of the County Public Water System have been sampled and contaminated lines isolated. All drinking water advisories have been lifted.

COPC = Fire-related contaminant of potential concern
DOH = Hawaii Department of Health