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Initial Post-fire Water Quality Results for Lāhainā, Maui

In response to community concern regarding coastal water quality after the Lāhainā fire, Surfrider Foundation Maui Chapter has initiated its Maui Post-Fires Water Quality Monitoring Program. 

We did not find evidence during our initial sampling run of fire-related contamination that would put human health at risk from recreation in the ocean. The metal concentrations we measured appear to be within the range of typical ocean water levels, and concentrations of both metals and Polynuclear Aromatic Hydrocarbons (PAHs) are well below the World Health Organization (WHO) recreational guidance and drinking water regulations set by both the Environmental Protection Agency (EPA) (link) and WHO (link). 

Our goal in collecting water samples near Lāhainā is to provide more information to the public regarding the safety of the water for recreational use. We are testing for heavy metals and PAHs based on feasibility of testing, toxicity to humans, and likelihood of suspension in the water. Metals can be released during fires from various sources including building materials, electronics, vehicles, and paints. In December, Maui County DOH released data showing high concentrations of heavy metals in ash samples collected in Lāhainā. PAHs are a class of chemicals that naturally occur in petroleum-based fuels and are well known carcinogens. PAHs are released into the environment through the incomplete burning of oil, gas, wood and other organic materials. PAHs are important to look at in ocean water as they can be transported long distances and pose health risks to humans.

We collected initial samples on January 10, 2024, less than 24 hours after nearly 4 inches of rainfall, to capture the impacts of stormwater, or the Brown Water event. We sampled eight sites: six within the burn area, as well as one site to the north at Canoe Beach (Hanakaʻōʻō) and one site further south at Olowalu surf spot. The samples were sent to Physis Labs in California for analysis. Typically, the turnaround time to receive data is approximately three weeks. However, the widespread storm events along the West Coast in early January led to a backlog of samples at the lab and delayed the processing of our samples.


Please read this blog post to learn more about our sampling plan and view our Standard Operating Procedures and Quality Assurance/Quality Control here

What are our results and what do they tell us?

The good news is that our data does not indicate a significant presence of fire-related metals or PAHs in the ocean where we sampled, at least not to a level that would indicate a dangerous human health risk. Overall, we didn’t see any dissolved metal concentrations, except for copper, that stood out as elevated beyond what we might normally expect to find at an ocean beach that is receiving stormwater runoff. Virtually no PAHs were detected, with the exception of very low concentrations at Lāhainā Harbor and Papalaua Street. This aligns with what investigators at University of Hawaiʻi  and U.S. Geological Survey found in their initial sampling  of ocean water and soil. Below we include additional details on how we compared and interpreted our data set. 

While our data does not indicate that there are major human health risks from the post-fire toxins that we tested for, it is important to note a few caveats that impact interpretation of this data set. These results are from a single sampling event. Additional testing is still needed for a better understanding of concentrations over time and during different weather patterns. Also of note, especially when looking at potential health risk, is the lack of specific recreational ocean water quality standards and relevant coastal water reference samples for both metals and PAHs. This can make it difficult for us to compare our results, as both WHO and EPA lack standards for a number of metals that we sampled for (see table below).

To access the complete data set, please follow link to results


Table 1. Dissolved metal concentrations (in micrograms per Liter of seawater) at Papalaua St. and Lāhainā Harbor on 1/10/24 

Screenshot 2024-04-09 at 11.34.00 AM
* non-metals

The above table shows the reporting limits for each of the metals tested, which sets the smallest concentration of a substance that can be reported by a lab. All metal concentrations fell well below any relevant standards, with the exception of copper at Papalaua St. and Lāhainā Harbor which did not exceed but came close to EPA standards for aquatic life. Blank cells mean that the metal was not detected. Blank cells under WHO and EPA columns indicate that there is no official standard for that particular metal. 


1 Lāhainā harbor samples had elevated levels of copper as well as very low levels of PAHs
2 Boat near Papalau St. a potential source of fuel based PAHs  
3 Papalau St. water samples had elevated levels of copper (2.310 micrograms/Liter) 
4 Wildfire particulates, like this ash in the beach at Papalua Street, are resuspended and dispersed by waves and tides. Their chemistry is represented in our unfiltered sample analyses. (Photo credit: Renee Takesue)


How did we interpret our results?

As a grass-roots organization dedicated to protecting and enjoying our ocean, waves and beaches, our sampling program aims to provide information on fire-related contaminants that might put recreational ocean users at risk. 

Unfortunately, there are no established standards for these metals and PAHs in recreational ocean water. There are, however, recreational screening values (World Health Organization), drinking water standards (Environmental Protection Agency, WHO), and aquatic life standards (EPA) that provide some reference to compare our data to in order to evaluate potential human health risks.  

The World Health Organization recommends screening values for recreational waters at pollutant concentrations that are 20 times higher than their Guidelines for Drinking Water. All of our results were well below these WHO recreational screening values. 

With the exception of copper in two samples collected in the middle of the burn zone, all of our data were also well below standards meant to protect both aquatic life as well as drinking water safety. Typically, aquatic life standards set lower thresholds than those for recreation, as they are meant to protect organisms that are in constant exposure to these chemicals. The same can be said for drinking water standards that are meant to protect human health from ingesting higher volumes of water than one might accidentally swallow during ocean recreation activities. The low level of metals from our results is a good indicator that we are not seeing pollution levels that would significantly threaten recreational safety in the ocean.      


How can ocean users be exposed to chemicals? 

Ocean users (surfers, swimmers, paddlers, etc.) may be exposed to chemicals in the waters through ingestion, inhalation, through the skin (dermal exposure), and through mucous membranes (e.g. eyes). There is a lot of variability in the potential health risk, and route of exposure, depending on how exposed your body is to the water and how much time is spent in the water. jeremy-bishop-zam3m6W2npM-unsplashThis makes the kind of recreational activity important in assessing risk. For instance, recreational activities with whole-body contact (ie. surfing, swimming) have higher rates of  ingestion and skin exposure than if you were paddling in a canoe.

People with open wounds are most vulnerable to being exposed to toxins and pathogens in the water. 

Metal results 

From a human health lens, dissolved metal concentrations in this data set are reported in micrograms/Liter (ug/L) or parts per billion (ppb), and are well below any recreational screening levels, drinking water standards, and aquatic life standards. 

Hawaiian volcanic soils naturally have high metal concentrations including aluminum, iron, manganese and titanium. Because of water and sediment inputs from the land, coastal ocean waters around Hawaiʻi typically have higher concentrations of these elements, relative to open ocean waters.

To better understand how our results fit with typical metal concentrations in seawater, we are collaborating with Nick Hawco, assistant professor and metals specialist at University of Hawai'i at Mānoa, who is leading the metal analysis for their Coastal Water Quality monitoring Program following the Lāhainā Wildfire. Project Leader Andrea Kealoha provided an in depth synopsis of their program and results during last monthʻs Maui Nui Marine Resource Council Know Your Ocean speaker series. 

In terms of fire-attributed metal concentrations, Nick and his team found elevated copper, lead, and zinc in their coastal samples. In the four samples they gathered since October, fire-related metal concentrations of copper and lead are declining over time. 

Nick provided his expertise and relevant data sets to assist in determining whether metal concentrations were likely attributed to natural geology or associated with the fire. Our results are in line with their study and show similar copper concentrations. Similarly we saw higher copper concentrations within Lāhainā harbor and Papalaua street than at other sites. Our results differ, however, in that we observed lower lead concentrations compared to the UH team.

Polycyclic Aromatic Hydrocarbons (PAH) results 

The only sites where PAHs were detected were Lāhainā Harbor and Papalaua Street. Physis Lab measured PAHs in nanograms/Liter (1000 times less than micrograms) or parts per trillion in unfiltered water samples (water plus suspended sediment). Please note that empty cells in the linked data sheet indicate that no PAH were detected. 

The PAH values were very low, and again, we ran into the issue of there being no recreational standard by which to compare our results. While not directly applicable, there are specific CDC guidelines for drinking water of these contaminants. Concentrations from our samples were below these drinking water standards. Also note that drinking water standards are significantly lower than recreational standards.

Renee Takesue of the United States Geological Survey has been studying PAHs since 2022 on Maui’s west side, as well as in post-fire ash samples. In addition to being chemicals of concern themselves, PAHs are helpful in detecting fire-derived material.  For example, the particular type of PAH is indicative of either fuel or combustion related sources. Similar to metals, the highest (and only) concentration of PAHs were in Lāhainā Harbor and at Papalaua St. Based on the type of PAHs that were detected at these sites, Renee suggested that there is likely a mixture of both fuel based PAH and fire-related PAH contributions. This makes sense in the context of the sunken boats in Lāhainā Harbor as well as the numerous burned vehicles around Papalaua street. The particular PAHs and relative concentrations in our samples resembled those in Lāhainā ash, which was collected November 8, 2023.

Researchers are finding thats because the fire was so hot, many of the organic contaminants often linked to fire (including PAHs) likely vaporized and are thus present in very low concentrations. This is evident in ash data (link) and leachate (link).  

Charcoal on the beach like this example from north of the Harbor, is one possible source of PAHs to coastal waters. (Photo credit: Renee Takesue January 15, 2024 sediment sample)


What does this mean for ocean safety?

In conclusion, we did not find evidence during our initial sampling run of fire-related contamination that would put human health at risk from recreation in the ocean. The metal concentrations we measured appear to be within the range of typical ocean water levels, and both metals and PAH concentrations are well below WHO recreational guidance and drinking water standards (EPA and WHO). 

Please note that areas within the burn zone are still restricted access and currently under contract for debris removal. Certain coastal zones and surf spots within the Lāhainā burn zone are not an option for ocean recreation at this time. As the coastal waters in Lāhainā burn zone have the highest probability of fire-related contaminants, the information from this data set is useful for giving more peace of mind in ocean recreational activities in surrounding areas. 

More testing is required to further understand how the Lāhainā fires have affected water quality in the near-shore waters where people recreate, especially as many contaminants like metals settle in sediment but can be resuspended by wave action or other turbulence.   

To best protect your and your family’s health, we continue to recommend avoiding any contact with the ocean, particularly near the Lahaina burn zone, during Brown Water Events, as stormwater runoff carries many different types of pollutants that can cause illness.  Swim and surf away from stream outlets and storm drains that also frequently carry pollution from the watershed down to the oceans and always rinse off with freshwater when you leave the beach. 

If you do get sick after swimming or recreating in the ocean, please make a report of it here

What's next?

Our goal is to continue sampling coastal sites in and near the burn zone for metals, most likely on a quarterly basis. We plan to sample an additional site that is further outside of the burn zone to provide good reference data that will allow us to better tease out and understand the influence of the fires on metal concentrations in the water locally . We also hope to collect samples during different weather and environmental conditions (i.e. waves, tides, wind and precipitation).

One site of particular interest that we aim to continue monitoring is makai of the Olowalu Temporary Debris Facility. Our initial samples were collected before use of this facility, providing us a baseline to monitor any potential changes in water quality that might occur with use of this site to store debris removed from the burn zone. 

All of these tests are being funded by the Surfrider Foundation Maui Chapter Wildfire Relief funds. Our last round of sampling was made possible by generous private donations. Each sampling round costs about $6,000.

Please donate if you would like to help us continue our post-fire monitoring program year round . 

If you have any questions regarding the data please email