What Pollutants Are Measured in the Air? - Ozone

When most of us hear the term “ozone”, we instantly think of the ozone layer and its beneficial role in protecting us from the most damaging rays of the sun. This is stratospheric ozone and although it has been depleted through the use of products containing chlorofluorocarbons (CFCs) and other damaging gases, a sharp reduction in the use of those gases means that the ozone layer is now repairing itself.

However, not all ozone is beneficial. Tropospheric ozone refers to that found at ground level and is a damaging contaminant which can not only endanger human health, but also cause damage to the environment by harming vegetation and contributing to climate change. This ground-level ozone is the main ingredient in smog as well and is a leading cause of localised air pollution.

Where does ozone come from?

Unlikely most harmful contaminants, ozone does not come directly from single anthropogenic sources. Instead, it is created through a chemical process involving pre-existing contaminants and sunlight. The two biggest contributors to ozone are nitrogen oxides (NOx) and volatile organic compounds (VOCs), which are generated by the combustion of fossil fuels in power plants, industrial facilities and private passenger vehicles, among other sources.

When NOx and VOCs come into contact with direct sunlight, a chemical reaction occurs which produces ozone. This is why ozone levels are more pronounced on the hot, sunny days of summer, though that doesn’t mean the contaminant is not present during winter as well. What’s more, ozone can easily be blown by the wind over large distances, meaning it is often found in heightened concentrations far from the original source of the NOx or VOCs.

What are the effects of ozone?

Prolonged exposure to excessive levels of ozone have been known to have a deleterious effect on the human body. As well as causing respiratory difficulties and exacerbating pre-existing health conditions like asthma, ozone can also irritate and inflame the eyes, nose and throat of those exposed to it. Over time, these can cause more serious health complaints, so keeping track of emissions monitoring data and avoiding the pollutant on days where it is found in particularly high concentrations is advisable.

Meanwhile, ozone is harmful for the natural world, as well. After being absorbed by the foliage of trees, flowers and other vegetation, high levels of ozone can negatively impact cell membranes and compromise the plant’s ability to photosynthesise, among other negative outcomes. This can manifest itself in less biomass, premature aging or discolouration of leaves, lower crop yields and reduced flowering periods and proliferation. What’s more, ozone is also thought to enhance the atmospheric capacity for retaining heat, thus making it a contributor to both global warming and climate change.

For those interested in learning more about ozone (and indeed all other forms of pollution and emissions), the upcoming CEM conference is scheduled to take place virtually in March and will provide in-depth coverage of all aspects of the topic.