We’ve written a quick guide to ozone, an air pollutant that’s increasing in the UK.
Ozone (O3) is a gas made up of three oxygen atoms. In ambient air, it is a pollutant of major public health concern and is estimated to have caused 489,000 deaths globally in 2021. According to the UK Government, ozone pollution exhibits a long-term upward trend, increasing from 40 µg/m3 in 1992 to 66 µg/m3 in 2023 (at urban UK sites, with rural areas higher). In this blog, we look at some facts about ozone and discuss the need for greater ozone monitoring.
Stratospheric ozone isn’t a problem, but tropospheric ozone is
When most people hear the word ozone, they probably think about the ozone layer and the problem of its depletion. The ozone layer is found in the stratosphere, the second layer of the Earth’s atmosphere, between 10 and 50 km above us. Here, ozone absorbs radiation from the sun, protecting life on Earth from dangerous levels of radiation. However, ozone can also form at ground level, in the air that people breathe. If inhaled, it can irritate and damage the respiratory system. It may also react with other substances in the air to produce particulate matter, a similarly dangerous air pollutant.
There are no major emission sources of ozone itself
Ozone is rarely emitted directly. It is known as a secondary pollutant because it is produced in the air from precursor chemicals. These precursors are themselves common air pollutants including nitrogen oxides and volatile organic compounds, which are released from vehicles, industry, and natural sources. Carbon monoxide and methane – largely from agriculture – also contribute to ozone formation.
The complexity of ozone formation and degradation makes pollution monitoring key
Ozone’s complex interactions with other substances make assessing and addressing exposure difficult. Common pollutants react to generate ozone, but others – such as nitric oxide – actually inhibit its formation, or break it down. As a result, the amounts and ratio of multiple key pollutants need to be measured to discern whether efforts to tackle one pollutant may inadvertently lead to higher levels of ozone.
There’s an “ozone season”
The greatest ozone concentrations tend to occur during spring and summer. Stable weather conditions and stagnant air can lead to the build-up of precursor pollutants, while more sunlight and higher temperatures increase the rate of ozone’s photochemical formation reactions. The weather changes associated with global warming are likely to increase ozone levels and bring about a longer ozone season. Furthermore, ozone is also a potent greenhouse gas (labelled a “super pollutant”), which may initiate a positive feedback loop leading to more warming and more ozone. However, this also means that air quality interventions can have climate benefits, too.
Ozone can have a surprising geographical distribution
Unlike most air pollutants, which generally have highest concentrations in towns and cities, ozone levels tend to peak dozens of kilometres away from urban centres. Often this is because of the relative absence of the other air pollutants that “mop up” ozone. Ozone is also influenced by international emissions. For example, the south-east of England typically has the UK’s highest concentrations of ozone because it is close to European sources of precursor pollutants. The UK Government state that future ozone trends will largely be determined by global emissions.
Enviro Technology’s ozone monitoring solutions
Ozone levels have been increasing and, with the effects of climate change and societal shifts to low-emission technologies, it is expected that more ozone will be produced and less will be degraded. In our previous blog on ozone and sulphur dioxide, we discussed the need to expand ozone monitoring capacity.
Only half of the UK’s national air quality monitoring network (AURN) sites monitor the gas, and only a fraction of these are in rural or suburban locations – where levels are often highest. While the UK Government must meet targets for ozone pollution, it is not included in local authorities’ statutory objectives for air quality management.
Enviro Technology have a range of ozone and ozone precursor monitoring solutions – from AURN-spec analysers to smaller instruments ideal for local government areas or community or organisation-scale initiatives. Get in touch with us today to find out more.
