Coastal Waters

Maui Wildfire Data: Nearshore Coastal Water Quality

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coastal water monitoring data.

Ash from the Lahaina wildfires may enter coastal water through surface water runoff and windblown ash. The ash may contain substances including arsenic, other metals, and asbestos, which can be harmful to human health. Stormwater best management practices (BMPs) throughout Lahaina have helped prevent runoff from carrying ash to the ocean, and spraying Soiltac® on soil and other surfaces has helped prevent winds from blowing ash into the ocean.

DOH and partners continue to monitor the quality of nearshore coastal waters. This monitoring helps to answer the following questions:

Have the Maui wildfires affected nearshore water quality?
Is it safe for people to swim, fish, and enjoy other forms of recreation in waters near Lahaina without significant health impacts caused by the wildfires?
Do additional steps need to be taken to prevent the settled ash in Lahaina from entering the ocean?

Two men and a woman testing water in the field. — DOH contractor team processing water quality samples at Olowalu surf break monitoring site.

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:

DOH collects routine water quality indicators every week from nearshore monitoring sites. These indicators include dissolved oxygen, pH, salinity, and turbidity. A summary of recent DOH data is presented here. DOH is also collecting nearshore water quality data for metals (total and dissolved), nutrients, and other water quality indicators to further evaluate potential impacts from the wildfires.
Hui O Ka Wai Ola (HOKWO) has collected water chemistry and nutrient data monthly or bimonthly from 12 sites in the Lahaina area. They will be assisting DOH in collecting upcoming quarterly monitoring for metals and nutrients. A summary of recent Hui O Ka Wai Ola data is presented here.
The Surfrider Foundation’s Maui Chapter collected grab ocean water samples on January 10, 2024, following a heavy rainfall event and analyzed the samples for metals and polycyclic aromatic hydrocarbons (PAHs). Surfrider sampling data can be found here.

The University of Hawaii at Manoa is conducting ongoing research on coastal water quality following the Lahaina fires. The UH results are summarized in a YouTube video from a public presentation on March 11, 2024.
U.S. Geological Survey (USGS) conducted limited water quality sampling and DOH is currently receiving and reviewing data from these sampling efforts. While the data provide context, they are preliminary and not suitable for decision-making. These data were not collected using DOH protocols or EPA protocols and methods, so DOH cannot verify the quality or representativeness of the samples or the analytical data. DOH is not using these data to inform decision-making.

Water Quality Data

DOH Data

To evaluate impacts from the wildfires, DOH and partners collect nearshore water samples from nine sites near Lahaina (Figure 1). The sampling occurs at seven beaches and two surf breaks.

Tables 1 through 3 present the summaries of coastal water quality sampling data collected by DOH during April 2024 for total and dissolved metals, nutrients, and conventional water quality parameters. Table 4 shows water quality data from various locations for temperature, salinity, dissolved oxygen, pH, and turbidity, comparing overall water quality data before and after the Lahaina fires.

DOH will continue to collect nearshore water quality samples and will post sampling results to this page.

Two people in a kayak on in the Lahaina Harbor — DOH contractor team sampling water quality from a sea kayak near Lahaina Harbor.

Figure 1. DOH nearshore water quality monitoring locations in Lahaina and surrounding areas. — **Figure 1.** DOH nearshore water quality monitoring locations in Lahaina and surrounding areas.

Please note Tables 1, 2, and 5 include DOH’s ecological Environmental Action Levels (EALs). Human health screening values for direct contact with surface waters are not available for these parameters, as further discussed in “What Do the Data Tell Us?” below.

Table 1. Results from nearshore water quality samples collected by DOH during April 2024 for total metals, in micrograms per liter (µg/L).

Parameters (Total)	DOH EAL: Surface Water Action Level for Marine Habitats (Ecological)1	Hanakao’o Park			Mala Wharf			Puunoa (Baby) Beach			Kamehameha Iki Park					Shark Pit - Puamana			Launiupoko Beach		Launiupoko Beach Surf Break	Olowalu Surf Break	Kahekili (Airport) Beach
Aluminum	—	10.7	11.1	62.9	78.5	15.4	17.6	37.2	52.3	45.6	508	101	94.6	78.3	81.8	77.4	79.2	66.6	6.52	6.76
Antimony	30	0.128	0.111	0.11	0.102	0.137	0.135	0.116	0.116	0.106	0.102	0.117	0.125	0.118	0.12	0.115	0.118	0.103	0.127	0.133
Arsenic	0.14	1.36	1.48	1.26	1.4	1.39	1.47	1.45	1.3	1.5	1.63	1.57	1.3	1.33	1.29	1.3	1.59	1.47	1.45	1.54
Beryllium	0.038	ND	ND	0.01	0.01	0.011	0.011	0.009*	0.01	0.01	0.019	0.011	0.011	0.011	0.011	0.012	0.012	0.013	0.012	0.011
Cadmium	9.3	ND	ND	0.006	0.007	0.01	0.01	0.013	0.006	0.007	0.009	0.006	0.006	0.015	0.009	0.006	0.005	0.007	0.007	0.004*
Chromium	50	0.165	0.217	0.328	0.362	0.228	0.205	0.216	0.291	0.293	1.35	0.39	0.377	0.382	0.37	0.345	0.381	0.378	0.218	0.237
Cobalt	23	ND	ND	0.02	0.018	ND	ND	ND	0.013	0.007*	0.318	0.035	0.046	0.034	0.04	0.033	0.034	0.039	ND	ND
Copper	2.9	0.058	0.061	0.172	0.19	0.276	0.297	0.145	0.163	0.177	0.604	0.204	0.171	0.159	0.152	0.127	0.214	0.214	0.101	0.246
Iron	—	5.4	3.96	36.1	43.5	4.24	6.91	10.9	19.1	15.3	393	40.3	42.7	33.4	41.4	30.9	45.7	40.4	2	1.93
Lead	5.6	0.004*	0.012	0.024	0.027	0.012	0.018	0.02	0.027	0.025	0.107	0.022	0.029	0.021	0.019	0.018	0.041	0.034	0.009	0.013
Manganese	—	0.692	0.642	1.62	1.79	1.03	0.874	1.01	1.21	1.2	8.47	2.43	4.67	4.13	3.19	3.11	2.42	2.28	1.15	1.31
Mercury	0.025	ND	ND	ND	ND	ND	ND	0.004*	0.004*	0.002*	0.004*	ND	ND	ND	ND	ND	ND	ND	ND	ND
Molybdenum	370	10	10.4	9.38	9.46	10.5	10.6	10.1	10.5	10.6	9.47	10	10.4	10.5	10.5	10.2	10	10.3	10.7	10.1
Nickel	8.3	0.157	0.122	0.248	0.251	0.183	0.215	0.211	0.221	0.224	1.5	0.295	0.309	0.285	0.296	0.259	0.368	0.336	0.195	0.227
Selenium	71	0.006*	0.005*	0.029	0.014*	0.025	0.026	0.023	0.028	0.018	0.022	0.021	0.024	0.029	0.022	0.014*	0.024	0.026	0.011*	0.024
Silicon	—	385	325	317	445	240	34	163	86	111	967	111	368	128	368	111	462	565	188	128
Silver	0.1	0.093	0.094	0.116	0.126	0.119	0.117	0.111	0.12	0.118	0.115	0.113	0.113	0.118	0.119	0.127	0.115	0.122	0.116	0.124
Thallium	12	ND	ND	0.007*	0.008*	0.009*	0.01	0.011	0.009*	0.008*	0.008*	0.009*	0.009*	0.011	0.009*	0.01	0.009*	0.009*	0.008*	0.011
Tin	—	ND	ND	0.019	0.016	0.018	0.025	0.027	0.027	0.016	0.022	0.024	0.016	0.017	0.015	0.017	0.019	0.021	0.02	0.03
Titanium	—	0.672	0.921	5.29	6.3	0.807	1.04	2.4	4.66	3.72	51.9	7.53	8.37	6.03	7.78	6.07	6.21	5.57	0.329	0.158
Vanadium	81	1.72	1.65	1.64	1.66	1.65	1.67	1.5	1.54	1.56	2.47	1.67	1.69	1.58	1.64	1.63	1.98	2.03	1.69	1.61
Zinc	86	ND	ND	0.919	0.988	1.29	0.811	0.877	0.927	0.991	2.4	1.02	1.42	1.25	0.63	1	0.9	0.925	1.1	1.45

Coastal water quality samples were collected by DOH in accordance with DOH protocols.
DOH EAL: Hawaii DOH Environmental Action Level for screening. An entry of “—” means the analyte does not have an EAL.
The table shows valid sampling results from the sites, including duplicate and triplicate samples collected for quality assurance purposes.
Concentrations higher than DOH EALs are shown in bold font.
ND: Non-detect
*Values were J flagged in the laboratory report, indicating that the result should be considered as an estimated rather than quantitative value.
¹Surface water EALs are for marine habitats and primarily consider potential harm to aquatic habitats or the potential for substances to accumulate in aquatic species. The EALs are from Table D-2b of DOH’s TGM EAL Surfer (found here: Environmental Hazard Evaluation and Environmental Action Levels – HEER Office (hawaii.gov)) from Spring 2024. Recreational water criteria for human health are based on bacteria levels in the water. See “What Do the Data Tell Us?” for explanations of why the levels shown here do not pose a risk to people using these waters for recreation.

Table 2. Results from nearshore water quality samples collected by DOH during April 2024 for dissolved metals, in micrograms per liter (µg/L).

Parameters (Dissolved)	DOH EAL: Surface Water Action Level for Marine Habitats (Ecological)1	Hanakao’o Park			Mala Wharf			Puunoa (Baby) Beach			Kamehameha Iki Park					Shark Pit - Puamana			Launiupoko Beach		Launiupoko Beach Surf Break	Olowalu Surf Break	Kahekili (Airport) Beach
Aluminum	—	ND	ND	5.6*	5.5*	7.01	5.69*	6.81	6.18	5.84*	8.54	8.61	8.21	7	8.46	6.64	4.46*	4.73*	ND	ND
Antimony	30	0.114	0.127	0.139	0.117	0.132	0.117	0.158	0.115	0.107	0.111	0.119	0.099	0.121	0.144	0.14	0.117	0.114	0.115	0.124
Arsenic	0.14	1.38	1.34	1.18	1.34	1.41	1.42	1.28	1.32	1.26	1.31	1.38	1.26	1.11	1.26	1.29	1.52	1.47	1.46	1.24
Beryllium	0.038	ND	ND	0.01	0.008*	0.01	0.01	0.011	0.01	0.012	0.012	0.011	0.01	0.011	0.011	0.01	0.011	0.01	0.009*	0.011
Cadmium	9.3	0.012	0.014	0.008	0.011	0.01	0.01	0.013	0.011	0.016	0.011	0.009	0.01	0.01	0.013	0.011	0.007	0.012	0.006	0.011
Chromium	50	0.179	0.19	0.247	0.257	0.196	0.215	0.226	0.209	0.234	0.185	0.193	0.22	0.246	0.24	0.343	0.323	0.401	0.328	0.261
Cobalt	23	ND	ND	ND	ND	ND	ND	ND	0.005*	ND	ND	0.007*	ND	ND	ND	ND	0.011	ND	ND	ND
Copper	2.9	0.069	0.106	0.177	0.093	0.256	0.273	0.153	0.169	0.175	0.162	0.145	0.115	0.176	0.132	0.134	0.127	0.121	0.117	0.154
Iron	—	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND
Lead	5.6	ND	0.003*	0.003*	0.004*	0.003*	0.003*	0.005	0.005	0.006	0.005	0.004*	0.004*	0.004*	0.003*	0.003*	0.003*	0.003*	0.004*	0.004*
Manganese	—	0.492	0.459	0.752	0.795	0.747	0.697	0.597	0.545	0.59	0.569	0.79	1.19	1.17	0.962	0.929	0.715	0.621	1.04	0.988
Mercury	0.025	ND	ND	0.013	0.014	0.006	0.007	0.025	0.024	0.018	0.018	0.017	0.015	0.016	0.015	0.015	0.005	0.004*	0.004*	0.004*
Molybdenum	370	9.77	10.5	9.33	10.2	9.8	10.4	10.4	10.5	9.33	10.3	9.55	7.44	10.1	10.3	10.3	10.1	10.3	10.2	9.96
Nickel	8.3	0.123	0.151	0.164	0.165	0.152	0.17	0.167	0.178	0.151	0.21	0.156	0.133	0.169	0.182	0.17	0.174	0.17	0.193	0.175
Selenium	71	0.016	0.025	0.015	0.027	0.032	0.037	0.033	0.029	0.029	0.026	0.022	0.029	0.031	0.021	0.013*	0.016	0.029	0.017	0.019
Silicon	—	565	745	591	685	436	556	471	377	359	864	505	702	505	659	531	1010	633	385	650
Silver	0.1	0.06	0.046	0.12	0.122	0.112	0.121	0.112	0.113	0.123	0.121	0.12	0.12	0.117	0.112	0.121	0.117	0.115	0.12	0.118
Thallium	12	ND	ND	0.01	0.009*	0.011	0.012	0.01	0.009*	0.01	0.009*	0.007*	0.01	0.011	0.012	0.011	0.009*	0.01	0.01	0.007*
Tin	—	ND	ND	0.025	0.02	0.008*	0.028	0.022	0.032	0.02	0.022	0.019	0.019	0.028	0.016	0.021	0.034	0.023	0.016	0.024
Titanium	—	0.267	0.064*	ND	0.088	ND	0.229	ND	ND	0.091	0.119	ND	ND	ND	ND	ND	ND	0.045*	0.218	0.285
Vanadium	81	1.71	1.71	1.45	1.45	1.58	1.46	1.5	1.36	1.39	1.21	1.3	1.33	1.5	1.35	1.51	1.9	1.76	1.62	1.63
Zinc	86	ND	ND	1.11	0.81	1.03	0.701	0.79	0.943	1.08	0.815	0.93	1.09	1.08	1.03	0.725	0.837	0.723	1	1.45

Table 3. Results from nearshore conventional water quality parameter sampling collected by DOH during April 2024, in milligrams per liter (mg/L).

Parameters	Hanakao’o Park			Mala Wharf			Puunoa (Baby) Beach			Kamehameha Iki Park					Shark Pit - Puamana			Launiupoko Beach		Launiupoko Beach Surf Break	Olowalu Surf Break	Kahekili (Airport) Beach
Ammonia (as N)	ND	0.078	0.075	0.06	0.061	0.063	0.011*	0.059	0.057	0.057	0.105	0.059	0.059	0.059	0.06	0.071	0.069	0.07	0.065
Dissolved Orthophosphate (as P)	0.0248	0.025	0.0209	0.02	0.0205	0.0204	0.0187	0.019	0.0192	0.0202	0.0176	0.0181	0.0185	0.0188	0.0205	0.0195	0.0226	0.0222	0.0219
Nitrate	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND
Nitrite	ND	ND	0.014*	0.0145*	0.0144*	0.014*	0.0151*	0.0145*	0.0145*	0.0142*	0.0147*	0.0144*	0.0145*	0.0139*	0.0138*	ND	ND	ND	ND
Total Alkalinity	113	119	110	117	111	115	115	114	116	116	120	115	117	115	115	119	117	115	115
Total Dissolved Nitrogen	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND
Total Dissolved Phosphorus	0.0548	ND	0.0645	0.0198*	ND	ND	0.0357	ND	ND	0.0215*	ND	0.0504	ND	ND	0.0367	0.0262*	0.0255*	0.017*	ND
Total Nitrogen	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND	ND
Total Orthophosphate (as P)	0.0249	0.028	0.0248	0.0248	0.0229	0.0227	0.0236	0.0245	0.0241	0.0263	0.0251	0.025	0.0241	0.0245	0.0282	0.0251	0.0246	0.0204	0.0207
Total Phosphorus	0.0285	ND	0.168	0.0566	0.262	0.0653	0.0637	0.0715	0.0859	0.0874	0.0496	0.245	0.0546	0.0732	0.0618	0.0451	0.0379	0.0252	0.017*
Total Suspended Solids	4.86	3.62	6.75	4.6	9.81	2.57	2.54	4.56	6.75	34	15.6	6.1	5.3	13	3.82	6.6	11.3	2.55	14.96

Coastal water quality samples were collected by DOH in accordance with DOH protocols.
DOH does not currently have Environmental Action Levels (EALs) for the parameters listed in the table.
The table shows valid sampling results from the sites, including duplicate and triplicate samples collected for quality assurance purposes.
Note that recreational water criteria for human health are based on bacteria levels in the water.
ND: Non-detect
*Values were J flagged in the laboratory report, indicating that the result should be considered as an estimated rather than quantitative value.

Table 4. Water quality data collected in West Maui before and after the Lahaina fires.

Pre/Post Fire1	Location2	Temperature (°C)					Salinity (ppt)					Dissolved Oxygen (mg/L)					pH	Turbidity (NTU)
		Min.	Max.	Avg.	Min.	Max.	Avg.	Min.	Max.	Avg.	Min.	Max.	Avg.	Min.	Max.	Avg.
Pre-Fire	Fire Impacted Sites (Hanaka'o Beach south to Launiupoko Beach Park)	23.4	29.5	26.6	33.10	36.40	35.20	5.11	7.06	6.25	7.98	8.32	8.15	0.75	43.70	7.02
Post-Fire	Fire Impacted Sites (Hanaka'o Beach south to Launiupoko Beach Park)	23.8	31.9	26.7	24.20	36.10	35.22	5.71	7.22	6.38	7.95	8.25	8.11	0.42	75.80	7.01
Pre-Fire	North Reference Area (Hanakaoo Point north to Kahekili Beach)	23.3	28	26.3	34.50	36.70	35.29	5.56	6.83	6.28	8.06	8.29	8.17	0.56	8.70	2.29
Post-Fire	North Reference Area (Hanakaoo Point north to Kahekili Beach)	23.5	27.6	25.7	34.97	35.90	35.45	5.77	7.01	6.25	7.95	8.25	8.12	0.65	10.90	2.93
Pre-Fire	Olowalu (Olowalu Shore Front to Mile Marker 14)	22.7	30.5	26.9	34.92	36.90	35.51	5.84	7.22	6.40	7.99	8.19	8.09	0.84	16.73	5.78
Post-Fire	Olowalu (Olowalu Shore Front to Mile Marker 14)	24	28.2	26.6	35.10	36.00	35.73	5.89	6.77	6.32	7.95	8.22	8.04	0.87	13.13	4.05

¹Pre-fire data range is from August 1, 2022, to August 7, 2023. Post-fire data range is from August 8, 2023, to March 31, 2024.
²Water quality data are based on DOH and Hui O Ka Wai Ola monitoring efforts.

Surfrider Data

Surfrider sampled eight sites in West Maui: six sites within the burn area, one location further north, and one location further south. This organization plans to continue collecting water quality samples for metals analysis on a quarterly basis and during “brown water” events. Table 5 presents the metal and PAH results from the eight sites for the January 10, 2024, sampling during a post-fire “brown water” event, after almost 4 inches of rainfall.

Table 5. Nearshore water quality data collected by Surfrider in West Maui on January 10, 2024, in micrograms per liter (µg/L).

Parameters	DOH EAL: Surface Water Action Level for Marine Habitats (Ecological)1	Canoe Beach 1	Canoe Beach 2	Mala Tavern	Mala Ramp	Papalaua St	Lahaina Harbor	505 Front St.	Shark Pit	Olowalu
Metals (Dissolved)
Aluminum	—	4.47	4.850	4.540	18.300	5.680	13.7	11.700	9.400	3
Antimony	30	0.133	0.175	0.215	0.086	0.255	0.196	0.259	0.186	0.274
Arsenic	0.14	0.839	0.954	0.931	0.366	1.410	1.060	0.967	0.734	0.977
Beryllium	0.038	ND	0.005	ND	ND	ND	ND	ND	ND	ND
Cadmium	9.3	0.003	ND	0.003	0.003	0.006	0.01	0.005	0.005	0.003
Chromium	50	0.079	0.081	0.038	0.093	0.228	0.131	0.031	0.024	0.071
Cobalt	23	ND	ND	ND	0.018	ND	ND	ND	0.008	ND
Copper	2.9	0.114	0.125	0.317	0.817	2.310	1.26	0.239	0.217	0.169
Iron	—	ND	ND	ND	2.770	1.570	1.2	0.944	3.5	ND
Lead	5.6	ND	ND	ND	ND	ND	0.014	ND	ND	ND
Manganese	—	0.22	0.244	0.447	1.08	0.56	1.66	0.669	1.04	0.417
Mercury	0.025	ND	ND	ND	ND	ND	ND	ND	ND	ND
Molybdenum	370	13.539	13.2	16	4.95	14	11.8	18.3	14.2	19.2
Nickel	8.3	0.184	0.224	0.397	0.163	0.508	0.352	0.332	0.274	0.352
Selenium	71	ND	0.005	0.014	ND	0.011	ND	ND	0.006	0.01
Silver	0.1	0.308	0.341	0.243	0.271	0.321	0.284	0.258	0.226	0.215
Thallium	12	ND	ND	ND	ND	ND	ND	ND	ND	ND
Tin	—	ND	0.465	0.026	ND	ND	ND	0.012	0.014	0.095
Titanium	—	ND	ND	ND	0.159	ND	ND	ND	ND	ND
Vanadium	81	1.41	1.560	1.480	1.520	1.450	1.5	1.450	1.390	1.470
Zinc	86	ND	ND	ND	ND	1.210	1.820	ND	1.640	ND
Polycyclic Aromatic Hydrocarbons (PAHs)
Benzo[e]pyrene	—	ND	—	ND	ND	0.00165	ND	ND	ND	ND
Biphenyl	0.5	ND	—	ND	ND	0.00131	ND	ND	ND	ND
Chrysene	0.018	ND	—	ND	ND	0.00125	ND	ND	ND	ND
Fluoranthene	7.1	ND	—	ND	ND	0.00208	0.00277	ND	ND	ND
Naphthalene	12	ND	—	ND	ND	0.00184	ND	ND	ND	ND
Phenanthrene	4.6	ND	—	ND	ND	0.00329	0.00395	ND	ND	ND
Pyrene	10	ND	—	ND	ND	0.00251	0.00246	ND	ND	ND

Water quality data provided from the Surfrider Foundation monitoring efforts.
DOH EAL: Hawaii DOH Environmental Action Level for screening. An entry of “—” means the analyte does not have an EAL.
Concentrations higher than DOH EALs are shown in bold font.
ND: Non-detect
PAH samples not collected for Canoe Beach 2 site
¹Surface water EALs are for marine habitats and primarily consider potential harm to aquatic habitats or the potential for substances to accumulate in aquatic species. The EALs are from Table D-2b of DOH’s TGM EAL Surfer (found here: Environmental Hazard Evaluation and Environmental Action Levels – HEER Office (hawaii.gov)) from Spring 2024. Recreational water criteria for human health are based on bacteria levels in the water. See “What Do the Data Tell Us?” for explanations of why the levels shown here do not pose a risk to people using these waters for recreation.

What Do the Data Tell Us?

Nearshore water quality monitoring conducted by DOH, Hui O Ka Wai Ola, Surfrider, and University of Hawaii continues to help DOH evaluate possible impacts of the wildfires on human health and the environment. Sampling to date shows that fire-related substances are not present at levels of human health or ecological concern. The coastal waters around Lahaina are safe for ocean recreation.

Ongoing nearshore monitoring data show that the water chemistry has stayed relatively consistent before and after the fires. This includes parameters such as temperature, salinity, pH, and turbidity. Conventional water quality parameters such as nutrient levels continue to be monitored to evaluate if they meet DOH water quality standards as set forth in Hawaii Administrate Rules (HAR) Chapter 11-54. DOH has developed these water quality standards to protect human health and aquatic life. The standards describe the desired condition of a water body, how the condition of the water body will be achieved, and controlling substances entering water bodies. Measured parameters to date fall within targeted ranges.

Based on ash data collected in the Lahaina and Kula burn areas, the fire-related substances of primary interest include metals. Therefore, water quality samples were analyzed for the same metals that were found at elevated levels in ash. To evaluate potential human health risk during recreational use of nearshore waters and ecological risks, DOH considered multiple lines of evidence. This included comparing sample results to the DOH Environmental Action Levels (EALs) for marine habitats (shown in the tables above) as well as other ecological screening values and health-based guidelines. The marine habitat EALs primarily consider factors such as bioaccumulation (how substances build up in an organism) and aquatic habitat toxicity. DOH also sets acute and chronic values for aquatic life for some metals under HAR 11-54, which generally align with DOH’s EALs. The U.S. Environmental Protection Agency sets ambient water quality criteria for some of the metals tested, which are comparable to DOH values.

Ecological screening values are typically set lower than criteria used for assessing potential risk to people using waters for recreation. However, no human health EALs have been developed for metals or other chemical substances for screening recreational waters. Public health agencies generally assess recreational water safety based on microbial criteria (like bacteria), which inform, for example, DOH Brown Water Advisory(ies). Setting guidelines for substances in recreational waters would need to take into account the multiple possible ways people may be exposed (e.g., the extent of skin contact, accidental ingestion) to these substances. The World Health Organization (WHO), however, recommends a simple screening approach for exposures associated with recreational activities. WHO recommends screening values at 20 times established safe drinking water standards to account for the small amount of water that may be accidentally swallowed during recreational activities. Collectively, fire-related substances tested in nearshore waters fall below WHO screening levels, indicating coastal waters around Lahaina are safe for recreation. 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.

Of note, Surfrider samples were collected during a “brown water” event, which likely reflects a worst-case condition for runoff and disturbance of any ash-contaminated sediments. Also, 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. A report on the background concentrations of metals in Hawaii sediments is located here.

Polycyclic Aromatic Hydrocarbons (PAHs)

PAHs were not detected in most Surfrider samples. Low concentrations of PAHs were measured at Papalaua Street and Lahaina Harbor, aligning with the results of similar water and soil sampling efforts conducted by other partners. Measured levels are well below health-based screening levels.