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Clark County is experiencing growing ozone pollution after nearly a decade decline, according to data from the county.
In the first half of 2021, Clark County reported 11 days when ozone levels exceeded the Environmental Protection Agency’s health standard of 70 parts per billion, compared with five days during the same period in 2020 and two in 2019, according to the Clark County Department of Environment and Sustainability’s Division of Air Quality. The highest reading of ozone for the county so far this year was 75 part per billion over an eight hour period near Mountain’s Edge.
In 2012, Clark County saw 43 days when ozone levels exceeded EPA health standards, but thanks to tougher emission standards and more fuel efficient cars, ozone pollution has steadily decreased over the years falling to a low of three days of excess ozone in all of 2019.
However, that trend has seen a reverse in recent years largely due to growing wildfires in the West and resulting ground-level ozone.
Ozone occurs naturally in the upper atmosphere, but when it’s produced at the ground level it can worsen chronic respiratory conditions like asthma and damage the ability of cells to combat respiratory infections, according to the EPA.
“Wildfire smoke, locally-produced ozone and transport of pollutants have all been factors in our exceedance days, so far,” said Paul Fransioli, senior air quality specialist for the county. “It’s been a mix of at least two of those three elements in our exceedances this year.”
Wildfire season across the West is starting earlier and ending later each year, fueled by long-term drought and climate change, which has contributed to air quality challenges year after year.
Wildfires throughout the Southwest have also been prevalent during four of the last five summers, including 2021, and along with more wildfires has come more days with excess ozone pollution.
“In July, a lot of excess ozone days were wildfire smoke influenced,” said DES spokesperson Kevin MacDonald.
In 2018, wildfires across Northern California brought Southern Nevada 35 days of ozone levels exceeding the EPA standard. While these wildfires may not originate in Southern Nevada wind often carries ozone and smoke pollution to the state.
“California’s ozone transports to our region and it settles here,” MacDonald said.
This year, California wildfires started earlier than previous years and California’s largest wildfire on record has continued for nearly three weeks and shows little sign of slowing down.
Whether the second half of the year will result in more excess ozone pollution than previous years is difficult to predict due to the various factors that contribute to ozone including weather patterns and wildfire. However, data shows high ozone pollution resulting from wildfires in the first half of the year can mean a longer wildfire season resulting in continued high ozone pollution the second half of the year, as Nevada saw in 2018.
“Those fires in Northern California are still going,” Fransioli said. “It’s kind of unpredictable how bad the fires will be and what kind of weather patterns will take that smoke where. I wish we had a crystal ball.”
Nevada is also dealing with the remnants of the Tamarack fire south of Gardenville which burned through more than 68,000 acres and destroyed or damaged more than a dozen structures.
“We’re so used to seeing hazy mountains out there it’s not even an exception anymore,” Fransioli said. “There’s not a direct wildfire plume where you can’t see the mountains but it’s a background bubble.”
Ozone forms when sunlight bakes chemical gases like nitrogen oxides and volatile organic compounds that are emitted by vehicles, power plants and wildfires.
Risk of ozone forming is the highest on sunny days with low airflow, making dry Southern Nevada an ideal petri dish. Stagnant weather conditions and the topographic structure of the Las Vegas Valley help trap these pollutants, causing levels to rise.
“One of the reasons ozone is a challenge here is because of our geography, our topography and our climate,” MacDonald said. “Southern Nevada becomes a perfect oven to cook ozone.”
And as Southern Nevada experiences more heatwaves and longer periods of triple digit temperatures the risk of ozone will only grow.
Vehicle emissions are the leading cause of air pollution in Southern Nevada, but record-setting high temperatures are also contributing to growing ozone creation, according to the county. Three of the previous five years were the hottest on record for Las Vegas.
To limit exposure to the highest levels of ozone in the summer, at-risk residents, such as the very old and very young, should avoid going outside.
Scientists have suggested that long-term ozone exposure appears to increase the risk of dying of heart and lung diseases. Other research found people living in areas with high ozone pollution are more likely to develop acute respiratory distress syndrome, a severe condition where the lungs fill with fluid. Recent studies have also linked wildfire smoke to a significant increase in COVID-19 cases in Nevada.
President Joe Biden recently met with governors from Western and Midwestern states to examine how federal intervention can best aid states fighting wildfires.
MacDonald said he would like to see similar regional cooperation between states and government agencies in an effort to come up with solutions to the growing air quality issues resulting from excess ozone and wildfires.
“Wildfires are something that’s becoming the new normal,” MacDonald said. “As these wildfires continue, and we’re getting more and more each year we have to start thinking regionally about how we’re going to address ozone and wildfires.”
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