Good Ozone vs. Bad Ozone: What’s The Difference?

Many of us have heard about the ozone layer in the atmosphere which is essential to human life and protects us from UV radiation. But there is also ‘bad’ ozone – a harmful air pollutant that poses a major threat to children and adult health. So what exactly is the difference between good ozone and bad ozone? And how can individuals and businesses benefit from accurate tracking of this invisible environmental hazard? We explain it all here.

What Is Ozone?

Ozone is an odorless and colorless gas found in the earth’s upper atmosphere as well as lower levels and even as low as the ground. An ozone molecule is made up of three oxygen atoms, which is why it’s typically referred to as O3.

The ozone “layer” that occurs naturally in the earth’s upper atmosphere extends to approximately 6-30 miles above the earth’s surface.

What Does Ozone Do?

Unlike other common air pollutants, ozone is both helpful and harmful to life on earth.

Good Ozone: Our Essential Sun Shield

The protective ozone layer which exists in the upper atmosphere is vital to life on earth. This ‘good’ ozone shields us from the sun’s harmful UV rays, which can cause skin cancer and destroy plants.

‘Good’ ozone in the earth’s stratosphere forms when UV radiation from the Sun breaks apart an oxygen molecule (O2) into two separate single oxygen atoms, which then bind with other O2 molecules and form O3 molecules, otherwise known as ozone.

For many years now, environmentalists have urged the world to stop manufacturing harmful CFC (chlorofluorocarbons) chemicals that destroy our upper ozone layer, such as freon refrigerants used in air conditioners. The international community agreed on the Montreal Protocol in 1987 to provide strict guidelines to limit the use of ozone-depleting substances in order to restore the ozone layer.

While the status of our atmospheric ozone layer has been improving over the last few years, a ‘hole’ still reappears annually between August to October in the Southern Hemisphere.

Bad Ozone: Ground-level Ozone & Impact on Health

Ground-level ozone is considered a secondary pollutant, created as a byproduct of man-made pollution released by fossil-fuel vehicles, factories, power and chemical plants, and other sources in the presence of sunlight.

Ozone also contributes to the typical “smog” or “haze” phenomenon we may experience in the summertime, although it can occur all year long in some regions.

How is Ground-level Ozone Formed?

VOC and NOx emissions from fossil-fuel-based/powered vehicles, power plants, industrial boilers, refineries, chemical plants, and other sources can undergo a chemical reaction in the presence of sunlight, forming ozone.

Additional factors that contribute to the creation of this ‘bad ozone’ are heat and sunlight, which is why ground-level ozone levels tend to increase during the summertime.

While ozone can also descend from the upper atmosphere to lower parts (troposphere), and although VOCs and NOx pollution can occur naturally in some capacity, the majority of ground-level ozone occurs as a byproduct of man-made air pollution.

Ground-level Ozone Pollution & Impact on Health

Ozone exposure can have a different impact depending on population group and sensitivity factors. 

The most vulnerable individuals are children since their lungs are still developing. Next are those with weakened immunity and/or existing respiratory diseases as well as those who spend a lot of time outdoors. 

The EPA warns that ground-level ozone can cause breathing difficulties, airway inflammation, and even aggravate chronic respiratory diseases such as asthma, sometimes causing school absences, visits to emergency rooms, and more. 

Exposure to ozone has also been linked to asthma development and other chronic conditions, and even death:

  • A long-term study looking at the health of Canadian children found ozone exposure at birth correlated with an 82% increased risk of developing asthma by age 3.
  • A global study of ozone-related mortality in over 400 cities found that more than 6000 deaths per year could be attributed to ambient ozone levels that exceeded the short-term World Health Organization guideline for ozone, of 100μm/m3.

When is Ozone Pollution Likely to be Highest?

As ozone requires the presence of solar radiation to occur, levels are likely to be highest on dry, sunny days. However, over the past decade, ozone concentrations during cold months have also increased in some high elevation regions where higher VOC and NOx emissions have led to the formation of ozone where temperatures are near or below freezing.

The Surprising ‘Weekend-Effect’

As man-made emissions contribute to ground-level ozone formation, you might assume this ‘bad ozone’ would also be lower on the weekends – when industrial work and road traffic tend to reduce activity. However, ozone levels can actually increase during the weekend.

This is because the formation of ground-level ozone depends not only on the concentration of NOx, and VOCs but also on the ratio of these different pollutants to each other, as well as the intensity of solar radiation.

As NOx is a primary pollutant emitted by vehicle emissions, when there are fewer cars on the road, there may be less NOx in the air. This might seem like a good thing for pollution in the city, but the impact on the overall ratio means urban centers can actually experience higher levels of Ozone during quiet periods. This is what’s known as the Weekend Effect of ground-level ozone.

Ozone Pollution: What Can We Do About It? 

Concentration levels of different pollutants will peak and dip at different times and locations based on a variety of climate conditions and other factors.

How Can We Measure The Levels Of Ozone In The Atmosphere?

Traditional ground-level ozone measurement methods rely on air quality monitoring stations that draw in air through a pump and shine UV light through the air to measure O3 concentrations.

However, these stations can only report on the ozone found in the immediate surrounding location, and can’t provide information regarding other locations between stations.

To overcome these limitations, BreezoMeter combines this station information with many other data sources, including weather, temperature, traffic information, and more. This multiple data-source approach enables us to forecast ozone and other pollutant concentrations and report live air quality conditions in a more real-time and granular level than traditional methods.

Practical Ozone Management Steps for Businesses & Individuals

BreezoMeter’s comprehensive air quality API and color-coded heatmaps enable businesses to make invisible pollutants like ‘bad ozone’ visible to users and engage individuals with personalized insights that relate to their own wellness and health.

Air quality reporting and managing ozone exposure isn’t about living in fear, it’s about empowering people to adopt healthier habits and capitalize on ‘smarter’ air-aware opportunities:

  • Health providers – can reduce care costs and improve health outcomes with actionable air quality insights warning of rising local ozone pollution levels.
  • Indoor air brands – can make platforms and products smarter by leveraging live ozone data to optimize indoor environment health management and even offer personalized air quality insights on the go via companion apps.
  • Lifestyle & fitness apps – can enable users to avoid harmful ozone exposure by tailoring recommendations based on local conditions: postpone outdoor activities during peak ozone hours or choose cleaner hiking/bicycling routes.

Ozone Pollution May Be Dangerous, But Access to the Right Information Means We’re Not Powerless

Live air quality data, location-based forecasts, and personalized air quality insights that include ozone-focused reporting enable businesses to distinguish themselves from competitors and meet rising consumer demands for better health tools and environmental awareness.

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Dr Gabriela Adler
Dr Gabriela Adler Katz

Chief Scientist @BreezoMeter. I hold an MSc & PhD in atmospheric science and formerly worked as a research scientist at NOAA. I believe it is my greatest duty as a scientist to bring science to the people!