7/8/2020 - Ozone Season “Halftime” Report:

Ozone Season "Halftime" Report:

Five exceedances over first three months is more than last year, fewer than most.

It's halftime of ozone season 2020 and how is Clark County faring? With five exceedances of the Environmental Protection Agency's 70 parts per billion threshold for acceptable levels of ground-level ozone thus far, the 2020 ozone season has already eclipsed last year's total but remains lower than previous years.

"Local weather conditions, homegrown pollutants and transport of pollutants from California have led to our exceedances," said DES Division of Air Quality meteorologist Paul Fransioli. "Indeed, we saw a decrease in pollutants right at the outset of ozone season, but many factors contribute to the formation of ground-level ozone."

May 6126Ozone (and related) precursor compounds in an airmass transported from the Mojave Desert near Los Angeles.
May 9112Transport of pollutants from southern California, wildfire smoke and recirculation of local air.
May 28118Local and regionally transported pollutants.
June 22126Local and regionally transported pollutants.
June 26108Weak airflow allowed ozone to increase during the day.

NOTE: This data has not been verified by the Clark County Department of Environment and Sustainability's (DES) Division of Air Quality and may change. This is the most current data, but it is not official until it has been certified by our technical staff. Data is collected from DES ambient monitoring sites and may include data collected by other outside agencies. This data is updated hourly. All times shown are in local standard time unless otherwise indicated.

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"We know we can expect hot, sunny weather," Fransioli added. "Beyond that, we will continue to monitor weather patterns throughout the western United States on a daily basis to provide up-to-date forecasts."

What Causes Ozone?
Ground-level ozone is formed when volatile organic compounds (VOCs) mix with oxides of nitrogen (NOx) in ultraviolet rays and heat. VOCs include fumes from fuel, paints and chemicals, and even some plants and vegetation. Examples of NOx are vehicle exhaust, factory emissions and wildfire smoke. Stagnant weather conditions and the topographic structure of the Las Vegas Valley help trap these pollutants, causing levels to rise. Exposure to ozone can irritate your respiratory system and cause coughing, a sore throat, chest pain and shortness of breath even in healthy people, according to the EPA.

How to Reduce Ozone
Since ground-level ozone is created by the chemical reaction of NOx + VOCs + UV rays, removing one of those elements can reduce ozone. DES builds in ozone reduction by drafting specific limitations on emissions for Clark County businesses when issuing permits.

"All of our air permits take NOx and VOC emissions into consideration," said Division of Air Quality Permitting Manager Ted Lendis. "Businesses must operate within the EPA's health-based standards on pollutant emissions or be subject to civil penalties."

DES also supports Nevada Gov. Steve Sisolak's Clean Cars Nevada initiative, which was announced last month. This initiative's goal is the adoption of new regulations to provide Nevadans with more choices for low- and zero-emission electric passenger cars and trucks at dealerships throughout the state beginning in 2024. With more than 1.4 million vehicles in Clark County, emission reduction at a macro level is crucial to ozone reduction.

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"While DES regulates emissions for local businesses, we have no jurisdiction over vehicle emissions in Clark County," said DES Director Marci Henson. "We've advocated for years to the state legislature to implement measures to help reduce vehicle emissions. Clean Cars Nevada is an important step to reducing ozone in our region."

For its part, Clark County has been reducing its fuel emissions for years, boasting the largest hybrid fleet of vehicles among state government agencies, including 58 all-electric vehicles. The Regional Transportation Corporation of Southern Nevada also works toward emission reduction, fueling 71 percent of its fixed-route bus fleet with compressed natural gas.

About the Department of Environment and Sustainability
The Department of Environment and Sustainability is the air pollution control agency, regional Endangered Species Act compliance program, and sustainability office for all of Clark County, Nevada. Established as the Department of Air Quality by the Clark County Commission in 2001, it was renamed in 2020 and is comprised of three divisions: Air Quality, Desert Conservation Program and Office of Sustainability. Through these three divisions, DES is ensuring the air we share meets healthful, regulatory standards, administering the County's Multiple Species Habitat Conservation Plan and addressing climate change.


Clark County is a dynamic and innovative organization dedicated to providing top-quality service with integrity, respect and accountability. With jurisdiction over the world-famous Las Vegas Strip and covering an area the size of New Jersey, Clark is the nation's 11th-largest county and provides extensive regional services to more than 2.3 million citizens and 45 million visitors a year. Included are the nation's 9th-busiest airport, air quality compliance, social services and the state's largest public hospital, University Medical Center. The County also provides municipal services that are traditionally provided by cities to about 1 million residents in the unincorporated area. Those include fire protection, roads and other public works, parks and recreation, and planning and development.

Last modified on 7/8/2020 13:39