Defending Community Air Quality for Clark County

Across the Western United States, wildfire smoke has become one of the most significant and least controllable drivers of air quality challenges.

In Clark County, Nevada, home to more than two million residents, even distant wildfires can send ozone-forming VOCs and fine particulates drifting into the Las Vegas Valley, triggering spikes that threaten ozone attainment status and reinforce misconceptions about local pollution.

Yet for years, they lacked a defensible, data-driven way to show when these exceedances were caused by transported wildfire smoke rather than local emissions.

For years, Clark County’s Department of Environment and Sustainability has operated under pressure to meet federal air quality standards.

Southern Nevada’s air quality metrics, particularly ozone, have drawn heightened attention from the Environmental Protection Agency (EPA) and national health organizations.

The irony? Much of what’s driving the problem isn’t even local.

“People look out over the valley, see haze, and assume our air is unsafe,” said Kevin MacDonald, Public Information Administrator for Clark County. “But a significant portion of what we’re dealing with originates elsewhere, in this case wildfires hundreds of miles away.”

Those wildfire emissions, rich with volatile organic compounds (VOCs) that serve as ozone precursors, can drift into the Las Vegas Valley long after flames are out. But until recently, proving that in an approach regulators would accept was nearly impossible.

Facing growing regulatory pressure and costly EPA fines, the county needed a defensible, data-backed way to distinguish wildfire-driven air impacts from local emissions.

That’s when they turned to Onterris, experts in air quality lab analysis and advanced VOC testing, and Spheros Environmental (formerly Sonoma Technology), research partners known for their work on exceptional event demonstrations.

Together, the team launched a multi-year air quality study across the Las Vegas Valley to answer one critical question.

When ozone and particulate levels spike, is it Clark County’s fault, or distant wildfire smoke?

Onterris worked alongside the Clark County team and Spheros Environmental to design a multi-year sampling plan that paired two complementary approaches:

• EPA Method TO-15 canister sampling to capture a broad suite of VOCs
• EPA Method TO-17 thermal desorption tube sampling to target wildfire-relevant VOC signals with an active sampling approach

The first season, in 2023, offered a calm start. Few wildfires meant little immediate data, but it became the perfect opportunity to fine-tune logistics and create a strong baseline of air quality in the area.

By 2024, wildfire smoke was back.

Through rigorous QA and QC, repeatable methods, and deep technical collaboration between Deer Park and Durham labs, Onterris turned every sample into a defensible story: when ozone levels rose, so did wildfire-specific tracers like acetonitrile and 2-butanone.

Using advanced Positive Matrix Factorization (PMF) modeling, the team built distinct “chemical fingerprints” separating local emissions (like vehicles) from wildfire plumes to support decision making, communication and regulatory documentation.

Three years in, Clark County now has hard evidence that wildfires play a measurable role in air quality exceedances. The data is being used in the county’s State Implementation Plan and Exceptional Event Demonstrations, critical documents regulators use to determine attainment status.

The project will continue through at least 2028, capturing additional wildfire seasons to strengthen the dataset. Each new year adds more statistical power and more credibility.

“This gives us a better story to tell,” said MacDonald. “We can show residents, regulators, even the media, that our air quality challenges often come from beyond our borders. Air quality here is better than people think, and we’re constantly taking steps to get better.”