Ground-Level Ozone: What It Is and Why It Is Dangerous

Ground-Level Ozone: What It Is and Why It Is Dangerous
By Steve LaNore, Certified Broadcast Meteorologist
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Ground-Level Ozone: What It Is and Why It Is Dangerous

Ground-level ozone makes for periods of poor air quality that cause health problems in many large cities worldwide. Ironically, ozone at ground level is dangerous, but the same ozone high in the atmosphere is essential!

What Is Ozone?

Ozone, also called trioxygen (O3), is a beneficial band of gas found in the Earth’s atmosphere that acts as a shield against ultraviolet radiation. Naturally occurring ozone surrounds the Earth in a layer about 10 to 25 miles (16 to 40 km) above Earth’s surface.

What Is Ground-Level Ozone?

Ground-level ozone, also referred to as tropospheric ozone, is a harmful gas found up to 2 miles above ground caused by oxides of nitrogen (NOx) and volatile organic compounds (VOC) that chemically react to each other. In other terms, ground-level ozone occurs when sunlight reacts with VOCs in the air like car exhaust, factory plumes, and chemical vapors to create harmful air pollution.

 What is Ozone Figure EPA
Photo Credit: Environmental Protection Agency (EPA)
Where Is Ground-Level Ozone Found?

Surface ozone concentrations are highest on days with sunny skies and light winds because gusty winds disperse the pollutants and cloudy skies disrupt the chemical reaction. Heavily populated areas have more vehicles, power stations, and industrial activity, so it makes sense that ground-level ozone will be higher in these areas as well. However, this is not always true.

  • Moderately sized cities located in valleys are vulnerable to bubbles of polluted air remaining trapped near the ground for days if there’s not much wind. The pollution makes conditions favorable for ground-level ozone to form when it’s sunny.
  • Areas downwind of metropolises like Houston or Chicago may occasionally get unhealthy concentrations of ozone when light breezes blow the unhealthy plume into town.
  • Southern cities in the U.S. have a longer ozone season than northern locations since the sunlight is more intense farther south through the cool months.

How Ground-Level Ozone Affects Your Health and the Environment

Ground-level ozone causes respiratory issues for some people. Ozone health effects may be quite minor, such as irritation of the nose and throat, or they could be more serious, like difficulty breathing. Individuals at high risk include:

  • People over 65 years old.
  • Children and teenagers.
  • Anyone who currently has respiratory diseases like asthma or chronic obstructive pulmonary disease.
  • Those who work outside and are exposed for much longer periods of time.
Environmental Impact

Ground-level ozone can be detrimental to the environment. It damages leaves and reduces a plant’s ability to grow, which can hinder entire ecosystems and vegetation over time. For farmers, ozone can be especially troublesome because it reduces crop yields, impacts seedling survivability, and makes plants more susceptible to disease and pests.

How To Reduce Exposure To Ground-Level Ozone

According to the American Lung Association, breathing in ground-level ozone is like “getting a sunburn on your lungs.” Here are a few simple practices to reduce the harmful effects of ground-level ozone:

  • Monitor National Weather Service air quality alerts to know when ground-level ozone is expected to reach unhealthy levels.
  • Exercise in the morning, when ozone levels are much lower than in the afternoon.
  • Remain indoors during the mid and late afternoon, or wear a mask if you need to go outdoors during this time.
  • Make sure doors and windows throughout your home are properly sealed. Use an indoor air quality monitor to ensure that pollution isn’t seeping inside.
  • Keep your heating, ventilating, and air conditioning filter clean to promote air circulation and reduce dust, which is also a respiratory irritant.
  • Consider getting an air filter containing activated carbon, which removes 60% to 70% of indoor ozone contamination.

Breathe Easier by Keeping Informed

Air quality alerts are usually issued a day in advance so you can plan to alter your activities and reduce ground-level ozone exposure. A home weather station from AcuRite will allow you to monitor changes in wind and sun levels, which are essential for predicting how the ozone levels will change. Stay weather-aware, and stay safe!

Steve LaNore is a certified broadcast meteorologist with more than 30 years of forecasting and technical experience. He has provided meteorological consulting for everything from insurance adjusters to court cases and is a nine-time award-winning author and broadcaster. LaNore has authored two books, available on Amazon. He resides in north Texas near beautiful Lake Texoma.
November 8, 2021
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