• What Are the Different Types of Air Pollution?

Air Monitoring

What Are the Different Types of Air Pollution?

Jan 07 2022

Did you know that an estimated nine out of every ten people are exposed to harmful levels of air pollution? That prolonged exposure is responsible for some 8.9 million premature deaths around the world each year. As a result, the UN has named air pollution as “the world’s worst environmental health risk” at the present time.

One might expect the situation to be better in the UK, given that the economy is strong, the infrastructure is well-developed and the country prides itself on its forward-thinking policies. However, tens of thousands people still succumb to maladies caused or exacerbated by poor quality air on an annual basis. Perhaps unsurprisingly, the British government has identified air quality as the biggest threat to public health right now.

But which pollutants are particularly prevalent in our airways? How did they come to be there? And what are the adverse effects of them on both human health and the wider environment? Here’s a rundown of six of the most common air contaminants, as well as a brief explanation of their origins and their impacts.

Particulate matter

Often described as the most damaging air pollutant from a human health perspective, particulate matter (or PM, for short) differs from most of the other pollutants on this list. That’s because instead of referring to a single gas or toxin, it instead encompasses a variety of different contaminants, some of which are composed of hundreds of different compounds and chemicals.

Generally speaking, particulate matter is divided into PM10 and PM2.5 The numbers here refer to the diameter of the particles in micrometres; for context, a human hair has a diameter of around 70 micrometres, so PM2.5 is roughly 30 times smaller! That’s pollution so small that it’s invisible to the naked eye, but which can be inhaled into the lungs and even absorbed into the bloodstream.

PM is often created when other contaminants react in the atmosphere, but can be produced directly from sources such as smokestacks, construction sites, unpaved roads and agricultural crops. PM has a range of damaging effects on the human body, including all types of cardiovascular and respiratory ailments. The full extent of its impact on our health is still not yet known.

Carbon dioxide

There is some debate as to whether greenhouse gases like carbon dioxide (CO2) constitute an air pollutant, since their impact is felt more in the long-term repercussions on the planet than the immediate quality of the air they inhabit. The fact that CO2 is a naturally-occurring facet of our world (it is exhaled by humans and animals) further muddies the waters.

In any case, there’s no denying that carbon dioxide is a gas which is heavily monitored and regulated by governments around the globe. As the gas with one of the most significant global warming potentials (GWPs), it can trap heat in the atmosphere and contribute to elevated temperature, extreme weather events and potentially the melting of the polar icecaps and the rising of the sea levels that would ensue.

Carbon dioxide is produced from many sources, including the aforementioned natural ones. However, the combustion of fossil fuels such as oil, coal and gas is a chief contributing factor, which is why world leaders are attempting to transition to cleaner sources of energy. Wind, wave and solar power are all renewable means of generating energy which do not entail harmful emissions of CO2 or other pollutants.

Carbon monoxide

Unlike CO2, carbon monoxide (or CO) is undoubtedly an air pollutant. In fact, it is regarded as being responsible for the biggest number of fatalities in many parts of the world if humans are exposed to it for many hours at a time. It’s for this reason that the installation of a working carbon monoxide detector is an urgent priority in homes and businesses around the globe.

Like CO2, CO is a naturally occurring gas in our environment. However, the chief sources of CO emissions today are those generated by manmade activity, such as power plants, vehicle exhaust pipes and the incomplete or improper combustion of carbonaceous materials. Deforestation, land clearing and stubble burning for agricultural or industrial purposes are other leading contributors of CO emissions.

Inhalation of CO over a period of just a few hours can cause serious health complications. Severe headaches can quickly turn into comas, and if the person is not removed from the environment and given immediate medical treatment, they can die. Meanwhile, CO can also react with UV radiation from the sun to create ozone, itself a damaging air pollutant.


When most people hear the word ozone, they immediately think of the protective layer which surrounds our planet and protects us from the full force of the sun’s rays. This is stratospheric ozone and it is highly beneficial to life on Earth. Tropospheric ozone, on the other hand, is a damaging contaminant found at ground level which is harmful to humans, animals and plants.

Ozone is primarily created when other contaminants in the air, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) react with sunlight. This generates particles of pollution which create smog in the atmosphere, inhibiting visibility and compromising the health of those who inhale them. Because UV radiation is needed to create ozone, it is more commonly found during summertime.

People who are exposed to high levels of ozone pollution can suffer irritation to their nose, eyes and throat, while it can exacerbate existing respiratory conditions such as asthma. At the same time, the foliage of plants and trees can suffer discolouration and damage from exposure to ozone, while it is also known to contribute to both global warming and climate change.

Nitrogen dioxide

Nitrogen dioxide (NO2) belongs to the nitrogen oxides (NOx) group of pollutants. It, like nitric oxide (also known as nitrogen monoxide, or NO), is produced primarily through the combustion of fossil fuels. Because NO is capable of morphing into NO2 after reacting with other atmospheric particles – and the same is true for NO2 turning into NO – the two gases are often simply referred to together as NOx.

Until fairly recently, power plants used to represent the biggest source of NOx emissions. However, stronger regulations and stricter compliance have seen the volume of NOx produced at such industrial facilities drop, meaning that road vehicles have since overtaken them as the leading producer of NOx. Other sources include gas stoves and other indoor heating appliances, as well as cigarette smoke.

Nitrogen dioxide is known to cause irritation and difficulties with breathing in those who suffer from respiratory conditions. It can also compromise soil quality and upset biomass chemistry in the natural world, while its role as a precursor to ozone means it has even more serious environmental consequences (outlined in more detail above).

Sulphur dioxide

Sulphur dioxide (SO2) is formed when any material such as coal, petroleum coke and fuel oil is combusted, since these substances all contain high levels of sulphur. As such, coal-fired power plants and ore extraction sites are among the principal sources of SO2 pollution, though large vehicles (like cargo haulers and locomotives) are also leading contributors.

Indeed, transport has overtaken heavy industry as the biggest source of SO2 emissions in recent years, given that stricter regulation of the latter has seen their emissions drop dramatically. Nowadays, the concentrations of SO2 in the atmosphere are not sufficiently high to pose a serious threat to either human or plant health, though it is a chief ingredient in the formation of PM, which is much more dangerous.

What’s more, SO2 can negatively impact the natural world around us. Excessive levels of sulphur in the atmosphere have been linked with extreme rainfall events, including acid precipitation, which is known to have a damaging effect on many types of flora and the ecosystems they inhabit.

How is air pollution monitored?

In order to gain greater insight into these various types of air pollution, governments around the globe have begun introducing greater regulation around the monitoring of emissions. This is achieved via the placement of sophisticated sensors which are capable of gathering real-world vehicle emissions data and identifying individual contaminants and quantifying their concentration in the ambient atmosphere.

As well as a growing network of such sensors controlled by governments, regional authorities and private citizens, it is also a legal requirement for companies which are responsible for a high level of emissions to collect their own information about their output. Achieving this compliance is crucial to the success of the business in question, since transgression can result in substantial penalties and fees.

As well as to achieve compliance with national and international legislation, this monitoring takes place to ensure that pollution levels are kept at an acceptable level with regard to human health, climate change and global warming. The technology involved in such monitoring stations is evolving all the time, with more advanced sensors providing greater insight into the behaviour of the contaminants.

For more information about these types of developments, the upcoming CEM conference is scheduled to cover the subject from all angles. Those interested in attending can do so online, since the conference will take place virtually this year due to the restrictions imposed by the coronavirus pandemic. See the above link for more details.

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