Contact: Kevin J MacDonald
Phone: (702) 455-6131

Clark County Ground-level Ozone Trending Downward

​       The air we share is improving in Clark County. An analysis of air quality data from 2003 – 2018 by Clark County's Department of Air Quality shows ozone exceedance days are trending downward. Last year's 35 exceedance days is a sharp decrease from 2003's 62 exceedance days. "Ozone season" for Clark County typically lasts from April 1 – Sept. 30 each year. What's leading to the downward trend? Several factors, according to Air Quality officials.

       "Auto emissions continue to improve, which helps lower ground-level ozone," said Air Quality Planning Manager Mike Sword. "The Department of Air Quality also enforces strict compliance with federal, health-based standards on all permitted businesses in Clark County to ensure they are not emitting unhealthy amounts of pollutants into the air."

What is Ozone?
       Ozone is a colorless gas that exists naturally in the Earth's upper atmosphere. At ground level, ozone is a key ingredient of urban smog that can build up during the day in the hottest months of the year because of strong sunlight, hot temperatures, gasoline and chemical vapors, and pollutants from automobiles, wildfires and regional transport. 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.

What is an Exceedance?
       According to the Environmental Protection Agency's health-based standards, an exceedance occurs when ground-level ozone levels are higher than 70 parts per billion (ppb) over eight hours in a day. The current 70 ppb standard went into effect in August 2018. The previous standard of 75 ppb was used from 2008 – 18.

       In 2018, Clark County has had a total of 35 ground-level ozone exceedance days—an increase over the previous five years due in part to local climate as well as wildfire smoke drifting into the region. Despite the increase, 2018 is still a sharp decline from 2003 – 2007 exceedance totals, which averaged 54 exceedance days per year.

       "The 70 ppb standard certainly played a factor in exceedances last year," said Sword. "Also, wildfire smoke was much higher last year in Clark County than in recent years, which contributed to about half of our ozone exceedances."

       Clark County is currently in "marginal" non-attainment status for ground-level ozone—the lowest classification—due in part to the EPA's implementation of the 70 ppb threshold this summer.

       "For the Department of Air Quality, this new, lower bar by the EPA simply means we have to limbo lower, which we will do," said Sword. "We beat dust and we beat carbon monoxide. Now, we will beat ozone."

 AQ Ozone Chart.png

Helpful Tips to Reduce Ozone
·         Because cars, trucks and other vehicles are major contributors to ozone, people can follow these helpful,
          everyday tips to reduce ozone:
·         Reduce driving – combine errands into one trip.
·         Don't idle your car engine unnecessarily.
·         Use mass transit or carpool.
·         Fill up your gas tank after sunset. Try not to spill gasoline when filling up and don't top off your tank.
·         Keep your car well maintained.
·         Consider landscaping that uses less water and gas-powered equipment to maintain.
·         Turn off lights and electronics when not in use. Less fuel burned at power plants means cleaner air.

       Also, if you have respiratory issues or other health concerns, consider these tips during ozone season:
·         Reduce the time you are active outdoors when ozone levels are elevated, especially if you are engaged in a
          strenuous activity or have a respiratory disease.
·         Schedule activities for the morning or evening when ozone levels are usually lower.
·         Substitute a less intense activity – walking instead of jogging, for example.

·         Always consult your doctor first for medical advice.


Last modified on 4/22/2019 17:00