Understanding Air Pollutants: A Guide to Ozone (O3)

What is Ozone (O3)

Ozone (O3 ) is a highly reactive gas composed of three oxygen atoms. It is both a natural and a man-made product that occurs in both the Earth’s upper (stratosphere), and lower (troposphere) atmosphere. Depending on where it is in the atmosphere, ozone can affect life on Earth in both beneficial and non-beneficial ways. Many people will be familiar with the ozone layer which is naturally occurring in the upper atmosphere and forms a protective layer from the suns rays. The less widely known form of ozone (sometimes referred to as tropospheric ozone) occurs in the lower atmosphere and is one of the most common pollutants impacting the quality of our air.


In contrast to many air pollutants, almost no ozone is directly caused by human activity. Instead, the ozone is formed in the air where high concentrations of energy interact with oxygen molecules. This can be high energy photons from the sun interacting high up in Earths stratosphere, or lightning in Earth’s lower atmosphere, or from reactions between other pollutants in sunlight. Tropospheric ozone is formed where concentrations of those pollutants are greatest, as sunlight causes reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs) – often near cities and industrial areas. Volatile Organic Compounds (VOCs) are generated in a variety of ways, and are often associated with the oil refining and petrochemical industries, whilst nitrogen oxides (NOx) originate from the combustion of fossil fuels in stationary sources, such as heating and power generation, as well as in motor vehicles.

Environmental Impact

Ozone itself is a greenhouse gas. As such, increasing concentrations of ground-level ozone contributes directly to global warming, and is significant as one of the pollutants causing the increase in the overall average temperature of earth’s atmosphere. Ozone is also generally an ingredient in the ‘smog’ which forms over large cities.

Tropospheric ozone has a significant impact on ecosystems, wildlife and plants. It can cause plants, trees and crops to suffer from slowed growth rate and has the potential to cause mass die-off in crops. Tropospheric ozone pollution is often seen to be an urban issue as it is in these areas where it is primarily formed. However, ozone also finds its way to more rural areas, potentially being carried hundreds of miles by wind or forming as a result of other sources of air pollution in these areas.

Health Impact

High levels of ozone gas can cause irritation and inflammation of the lungs, as well as irritate the eyes, nose and throat which can lead to persistent coughing and chest discomfort. This is of particular concern for asthmatic individuals, as ozone pollution episodes can increase breathing difficulties. Studies across Europe, Asia and North America have repeatedly found that risk of premature death increases with higher levels of ozone pollution.

Depending on level of exposure, ozone can cause coughing and sore throats, inflame and damage airways, aggravate existing conditions such as asthma and make the lungs more susceptible to infection.

Sensit by Crowcon RAMP

The Sensit RAMP is a robust, remote and reliable low-cost air quality monitoring platform. The device is capable of monitoring up to five gaseous chemical pollutants. The device uses a laser scattering detection method to detect both PM2.5 and PM10 with a range of 1-1000 μg/m3.

The RAMP is suitable for use in a variety of industries including construction, transport, waste, oil and gas, chemical and petrochemical industries.

What are VOCs?

The nature of gas hazards posed by some working environments can be complex and complete protection is not available from a single solution. This week, our guest blogger, Richard, takes a look at VOCs: how they pose a hazard and what we can do to protect against them.

Continue reading “What are VOCs?”