When we think of ozone gas, we often picture the ozone layer that protects life on Earth from the sun’s harmful UV rays. But at the ground level, the same protective ozone gas can be incredibly harmful for everyone and even the health of the planet. Breathing ozone can worsen respiratory illnesses like asthma.
We have a federal Air Quality Index that measures levels of particulate matter and ozone and interestingly enough, we can sometimes detect ozone by its distinct smell. Ultimately, it’s important to understand the basics of what ozone is, what ozone smells like, how ozone can impact your health, and the different ways you can minimize your exposure to ozone.
What is ozone?
Ozone is, in the most basic sense, a form of oxygen. Each molecule of ozone is made up of three oxygen atoms (O3); the oxygen we breathe, on the other hand, is made up of two atoms. Ozone occurs in two layers of the atmosphere: the stratosphere and the troposphere. Depending on where ozone is in the atmosphere, it can be good or bad for your health.
Ozone in the stratosphere
At the highest level, ozone in the stratosphere (the ozone layer) sits between 6 and 30 miles above the Earth’s surface and has one main job: to protect life on Earth (including you!) from the sun’s ultraviolet (UV) radiation. The stratospheric ozone layer is naturally broken down and replenished.
However, scientists and researchers have found that man-made chemicals are causing the ozone layer to deteriorate. These chemicals are referred to as ozone-depleting substances (ODS). When the ODS are released into the air, they degrade slowly as they make their way from the Earth to the stratosphere. Once ODS reach a high enough level, the intensity of the sun’s UV rays break them down, releasing chlorine, bromine, and other radicals, which destroy the “good” ozone layer.
When this happens, a greater amount of UV radiation reaches the surface of the Earth. This UV ray exposure can be harmful to plants, animals, and humans, potentially causing skin cancer, cataracts, and suppressed immune systems.
Ozone in the troposphere
Ozone found closest to the surface of the Earth, present in the troposphere, is considered an air pollutant and is very harmful to the health of all living things. The troposphere extends to approximately 6 miles above the Earth’s surface, where it meets the stratospheric (or “good”) ozone layer. This ground-level “bad” ozone is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs). This occurs when polluting emissions from cars, factories, power plants, and other human activities react in the presence of sunlight.
During the hot summer months, ground-level ozone pollution is a big concern. The sunlight and heat result in harmful ozone concentrations in the air. While urban areas are most impacted by ozone pollution, winds can carry the emissions hundreds of miles away, making it a concern for rural areas, too.
Though it’s critical that we take steps to reduce the use of ozone-depleting substances and work to restore the stratospheric ozone layer, it’s also important to learn how to protect ourselves from the damaging effects of ground-level ozone. That’s what we’ll be focusing on for the rest of this article.
What does ozone smell like?
Have you ever heard the phrase “smells like rain?” Well, people who say they can smell a storm coming are correct. What they’re really smelling is ozone. In fact, the word ozone is derived from the Greek verb ozein, which means “smell.” This is particularly fitting given the strong aroma of this chemical compound.
Ozone has a distinctive smell that humans can detect even in small concentrations — as few as 10 parts per billion.
Here are some of the ways the smell of ozone is described:
- Like a burning wire
- Like chlorine
- A “clean” smell
- Sweet and pungent
- Like an electrical spark
Knowing what ozone smells like can help you detect whether there are high concentrations in the air. Because there are significant health risks associated with ozone exposure, the smell of ozone can alert you to take necessary precautions.
What are the health effects of ozone?
Ozone, at the stratospheric level, protects you and the Earth from harmful UV radiation. If you have ever worn sunscreen before heading out to the beach or park, you are likely familiar with the harmful health effects of UV radiation. You use sunscreen to protect yourself against skin damage, including cancer, which is caused by this type of radiation. These aren’t the only damaging effects of high exposure to UV rays, though — cataracts and a suppressed immune system can also occur. This is one of the main reasons scientists are very concerned about the depletion of the protective ozone layer and how to restore it back to its natural state.
However, on the ground-level, ozone is a pollutant that has a plethora of other negative health effects, even in relatively low amounts.
Who is most at risk from exposure to ozone?
Though breathing in ozone is dangerous for everyone, there are certain groups of people who are at a higher risk of developing health problems from the gas. These include:
- People with asthma
- Older adults
- Outdoor workers
- People with vitamin C and E deficiencies
(*Children makes this list because their lungs are still developing, and they are more likely to be active outside than adults are. Children are also more likely to have asthma.)
What are the symptoms of ozone exposure?
Even in healthy people, ozone exposure can cause significant health problems. Most of these issues are related to the respiratory system and lungs. According to the Environmental Protection Agency, the effects of breathing in ozone include:
- Induction of respiratory symptoms
- Reduced lung function
- Inflammation of airways
Studies have found that even short-term exposure to ozone (up to 8 hours) can cause symptoms such as:
- Chest tightness
- Shortness of breath
- Throat and lung irritation
- Pain when breathing deeply
Many of these symptoms are linked to the narrowing of the airways. Thankfully, these ozone exposure symptoms can be reversed. However, the effects of long-term exposure may not be reversible, making it critical to control the amount of ozone you and your family are exposed to.
The potential long-term effects of ozone exposure include:
- Susceptibility to respiratory disorders like asthma, pneumonia, and bronchitis
- Scarring of the lungs, causing long-term impairment of lung capacity (or the volume of air that the lungs can expel)
- Reduced ability of the immune system to fight bacterial infections in the respiratory system
How can you reduce exposure to ozone?
It is important to take steps to reduce your exposure to any high ozone levels occurring outdoors and the lower ozone levels present indoors.
Check your outdoor air quality
First and foremost, you should check your outdoor air quality. If ozone levels are high, consider staying indoors as much as possible and closing the windows. You may want to forego exercising outdoors, doing yard work, or walking or biking to work. Being highly active when ozone levels (or even pollen levels, if you have bad allergies) can cause you to breathe in more of the pollutant. Wait until evening, when the temperature is cooler to do outdoor activities.
Reduce ozone levels indoors
Most of our exposure to ozone happens outdoors, but as much as 45% to 75% of an individual’s overall exposure to ozone happens indoors. When ozone levels are high outdoors, make sure to close the windows and reduce the ventilation rate from the outdoors. Regarding indoor air purifiers, you may be able to reduce your exposure by using filters containing activated carbon, but other filters, especially those that only remove particulate pollutants, will not be effective. Also, be careful if you use anything indoors that produces high concentrations of ozone, like plasma cutters, welders, or ozone generators.
Be careful when using ozone generators
Many people who want to improve their indoor air quality have turned to ozone generators. These are air purifiers that intentionally produce ozone, which claims to deodorize, disinfect, and remove dangerous particles in your home’s air.
The Environmental Protection Agency (EPA) does not recommend using ozone generators to clean indoor air. They say this is primarily because "scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants."
Though some vendors may suggest that their company’s ozone generators have been approved in some way, there are no government entities that approve the use of ozone in occupied spaces.
Reduce your contribution to ozone pollution
Aside from being conscious about your personal exposure to ozone on a daily basis, you should also consider ways to reduce your contribution to ozone pollution. The EPA gives us some great ideas, including:
- Conserve energy – at home, at work, everywhere.
- Carpool, use public transportation, bike, or walk whenever possible.
- Follow gasoline refueling instructions for efficient vapor recovery, being careful not to spill fuel and always tightening your gas cap securely.
- Keep car, boat, and other engines properly tuned.
- Be sure your tires are properly inflated.
- Use environmentally safe paints and cleaning products whenever possible.
- Mulch or compost leaves and yard waste.
- Avoid excessive idling of your automobile.
- Refuel your car in the evening when it’s cooler.
- Conserve electricity and set air conditioners no lower than 78 degrees.
- Defer lawn and gardening chores that use gasoline-powered equipment, or wait until evening.
Ozone pollution is a serious health concern that has become common in our industrialized world. The first step is awareness, which leads to individual action, and ultimately, to improvements made on a global scale. Many countries of the world have already come together in a commitment to restore the depleting ozone layer, and the EPA’s Clean Air Act and subsequent policies have improved ozone pollutant levels. We can take individual steps to lower our exposure and let the ozone smell before a storm cause us to remember.