5 Pollutants Measured by the AURN

First established in its current format in 1998, the Automatic Urban and Rural Network (AURN) is the largest automatic air quality monitoring network in the UK. At its inception, it consisted of 103 monitoring sites across the country, though that figure has since swelled to over 170, each of which employs cutting-edge technologies and methodologies to meet standards and ensure compliance.

Indeed, the network was launched in order to allow the UK government to gather, document and report on a number of pollutants as mandated by the EU’s Ambient Air Quality Directives. Although the AURN does not track all of the contaminants listed in the Directives, it does detect and quantify concentrations of five of the most prevalent and dangerous from a human and environmental perspective. These five substances are investigated in more detail below.

Carbon monoxide (CO)

For most of us, CO is associated with the detectors which UK law now obliges all homeowners to install in their kitchen. That’s because the gas is odourless, colourless and does not produce any noticeable symptoms immediately upon inhalation – until it’s too late. In poorly ventilated spaces, it can kill humans in even small concentrations, earning it the moniker of the silent killer. Outdoors, however, it’s more effective at trapping heat in the air and contributing to global warming.

Nitrogen dioxide (NO2) and nitrogen oxides (NOx)

NO2 and NOx are primarily produced when fossil fuels (such as oil, gas and coal) are combusted and both gas types can be converted from one into the other. In urban environments, the principal contributor of such emissions is the tailpipe exhausts of road vehicles. As well as being damaging to human health, NOx is also one of the key ingredients in the formation of ozone (see below), meaning it poses a double threat for air quality.

Ozone (O3)

There are two types of ozone: stratospheric ozone and tropospheric ozone. The former is actually beneficial for the planet, since it shields us from the most damaging UV rays of the sun. The latter, however, is produced when NOx and polycyclic aromatic hydrocarbons (PAHs) react with sunlight. It’s the main ingredient in urban smog and can contribute to a variety of respiratory ailments, such as asthma, as well as damaging flora and fauna.

Particulate matter (PM)

PM is one of the most widespread contaminants in our airways – as well as being one of the most deadly. It is microscopic in size (PM2.5 has a diameter 30 times less than that of a human hair), which means it can be easily inhaled into the lungs and even the bloodstream, damaging the body as a result. It can be produced directly from a single source (such as from a construction site or smokestack chimney), or else as a natural reaction between other contaminants and elements.

Sulphur dioxide (SO2)

SO2 is produced naturally when volcanoes erupt, but the proliferation of heavy industry over the last 200 years had seen its concentrations leap up through the combustion of fossil fuels with high sulphuric content. Thankfully, legislation has reduced emissions of SO2 from this source, but the transportation sector remains a major contributor. SO2 is a chief ingredient in PM and can be damaging for humans when they are exposed to it in high concentrations.