Particulate Matter

Maui Wildfire Data: Air

Particulate Matter in Lahaina

PM₁₀

PM_2.5

Click here to download the complete set of 1-hour PM₁₀ air monitoring data.

Click here to download the complete set of 24-hour PM₁₀ air monitoring data.

Air page text and figures are current through July 2024. For most recent data, click here.

Ash that is in the air is in particles of different sizes. Since the beginning of debris removal operations on January 13, 2024, DOH has continuously measured the amounts of particles in Lahaina’s air. These measurements of “particulate matter” (or PM) are indicators of airborne ash and dust. PM is of health concern because it is small enough to enter people’s lungs.

DOH measures two different sizes of particles: PM₁₀ and PM_2.5. Measurements of these particles to date have consistently been below levels that are protective of public health.

PM₁₀ Findings

PM₁₀ are airborne particles that are smaller than fine grains of sand—and they are smaller than the thickness of human hair. PM₁₀ comes from many different sources, like wind-blown dust, construction, cars, and agriculture. PM₁₀ measured in Lahaina could contain ash from the fires, as well as dust and particles from other sources. Since January 13, 2024, DOH has collected daily PM₁₀ samples at the Lahaina Intermediate School, the Lahaina Boys & Girls Club, the Leialii Hawaiian Homelands, and one of the Lahaina wastewater pump stations. Airborne PM₁₀ levels at these four locations changed from hour to hour, and 24-hour average (or daily) levels were compared to EPA’s health-based air quality standards.

Health Findings

For the time period noted above, with one exception, every daily PM₁₀ sample that DOH has collected to date at its four community monitoring stations in Lahaina has been below levels that are protective of public health. The exception was the daily PM₁₀ sample collected on May 15, 2024, at the Lahaina Intermediate School. No debris crews were working nearby, and visible dust was not observed in the area, so debris removal operations are not believed to be the cause of this one elevated concentration.

PM₁₀ samples that the U.S. Army Corps of Engineers (USACE) and its contractors have collected at debris removal sites and at the Temporary Debris Storage Site over the same time frame have also been below levels of health concern (click here to access the USACE data files). The data collected at these worksites have been consistently below levels that would pose unacceptable health risks for occupational exposures.

What is being done to reduce exposures to airborne particles

Many steps are being taken to make sure no one is exposed to unhealthy levels of PM₁₀. Soiltac® has been sprayed on the ash to keep it in place, and debris removal and TDS Site operations use various strategies—like water sprays—to control dust and keep ash out of the air. DOH will continue to collect daily air samples of PM₁₀ at four locations in Lahaina and will post advisories to this website if potentially unhealthy levels occur.

PM_2.5 Findings

PM_2.5 are airborne particles that are so small that they can go deep into your lungs. PM_2.5 in Lahaina could contain ash from the fires, and it could also come from other sources. DOH started its PM_2.5 air quality monitoring in Lahaina in January 2024, which was before debris removal operations began. DOH has continuously measured PM_2.5 at 50 locations throughout Lahaina since then. USACE also monitors PM_2.5 at debris removal locations and at the Temporary Debris Storage Site.

You can view current conditions using the map below, which provides Air Quality Index (AQI) advisory levels for sulfur dioxide (SO₂) and PM_2.5. For more information on the advisory levels and how to use them, click the FAQ icon. To limit the map to a single pollutant, or limit the types of monitors displayed, click the Filter icon.

Please note that isolated spikes in the AQI values seen on the map above, particularly from temporary (triangular) and non-regulatory (square) monitors, could be attributable to a variety of short-term pollution sources such as outdoor grills, idling vehicles, or lawnmowers. Isolated spikes can also be due to limitations of the sensors. These data should be used for informational purposes only.

Health Findings

Note that the real-time data on the map above are preliminary and unofficial. The data await review and validation by qualified staff. The data may be revised or invalidated after review. DOH makes every effort to assert the validity and integrity of the data, but data can be affected by equipment malfunctions, technical difficulties, and other unforeseen circumstances.
You can access the USACE PM_2.5 monitoring data for debris removal locations and the Temporary Debris Storage Site. All measurements to date at these locations have been below levels of health concern.

Recommendation to residents

Continue to protect yourself from PM_2.5 and other harmful substances in ash. You can get real-time information on PM_2.5 levels in Lahaina and instructions for avoiding unhealthy exposures from www.hiso2index.info and further instructions for avoiding unhealthy exposures from https://fire.airnow.gov. If you do not have access to these websites, take caution if you are in a location where there is visible dust or if the ash will be disturbed. To limit the amount of PM_2.5 you might breathe in, you can either temporarily leave the area or wear a snug-fitting dust mask or N95 mask—look for the words “NIOSH Approved” printed on the mask. Read more about how to protect yourself in DOH’s Maui Wildfires Air Quality Guide for Particle Pollution fact sheet.

What is being done to reduce to exposures airborne particles

Many steps are being taken to make sure no one is exposed to unhealthy levels of PM_2.5. Soiltac® has been sprayed on the ash to keep it in place, and debris removal and TDS Site operations use various strategies—like water sprays—to control dust and keep ash out of the air. So long as debris removal occurs, DOH will continue to measure PM_2.5 throughout Lahaina and will post advisories to this website if potentially unhealthy levels occur.