• What Is the AURN? - Network, Methods and Benefits

Air Monitoring

What Is the AURN? - Network, Methods and Benefits

Aug 10 2022

Breathing is such a natural and integral part of daily life that most people give no thought to the air they inhale whatsoever. However, the growing trend of urbanisation experienced over the last few centuries has seen more and more people crowd into densely populated areas, while increased industrial activity and widespread transport networks have contributed to poorer quality airwaves.

In fact, the World Health Organisation (WHO) estimates that more than 90% of the global population is exposed to unsafe levels of air pollution today. Obviously, there are some parts of the world where the situation is more serious and the risks are higher than others, but even in developed nations like the UK, air pollution remains a serious issue. It’s believed that hundreds of thousands of people lose their lives prematurely in the EU to poor quality air each year, with life expectancy reduced by an average of nine months among those exposed to airborne contamination.

In order to counteract this growing problem, the EU has introduced strict legal guidelines which oblige member states to gather, document and share information on the concentration of various pollutants in their jurisdiction. In response, the UK has implemented a number of systems geared towards that end, culminating in the creation of the Automatic Urban and Rural Network (AURN) in 1998.

For those interested in learning more about what the AURN is, its aims and motivations, the methods via which its data are collected and the purposes to which they are put, this explanatory guide should give you a brief introduction to the topic.

A brief history of air pollution monitoring in the UK

In the 1950s, the Great Smog of London claimed the lives of approximately 4,000 people, leading to the establishment of the Clean Air Act in 1956. Over 60 years later, achieving clean air still remains a political objective for those in power – perhaps even more so than ever before.

While air pollution data has been collected in the UK for decades, the first automatic system (the Statutory Urban Network) did not surface until 1987 and came into being as a direct response to the EU Directive which mandated maximum thresholds for a variety of air pollutants. In 1992, it was complemented by the creation of the Enhanced Urban Network, which was expanded further the following year and then amalgamated with the Statutory Urban Network in 1995 to form the Automatic Urban Network. At this time, it encompassed 30 monitoring stations in urban epicentres throughout the UK, though 50 more would be added in the next five years.

It wasn’t until 1998 that town and countryside monitoring networks were combined to create the Automatic Urban and Rural Network (AURN). At its inception, it consisted of a mere 103 sites, though that figure had swelled to 171 by February 2021.

What is the AURN?

Simply put, the AURN is the largest network of automatic air monitoring sites in the UK today. It is the main resource used when assuring compliance against the Ambient Air Quality Directives, which dictate the maximum concentration levels that are deemed safe for a variety of pollutants in the country. It can also be freely accessed by the public using the AURN’s dedicated website.

Why was the AURN established?

With 56.3 million people in the UK (83% of the national population) living in urban environments, the role of monitoring in maintaining good air quality in towns and cities cannot be underestimated. The AURN was set up to help achieve this aim, as well as to comply with national and international regulations on the issue.

At the time of its foundation, the UK was still a member of the EU and thus beholden to its legislation on air pollution. In particular, the Ambient Air Quality Directives specify that concentrations of certain contaminants must not exceed a specific threshold for more than a fixed period of time or number of days per year. Transgression of these directives is punished by fiscal penalties. The AURN, then, is instrumental in monitoring compliance with that legislation.

Of course, the UK has since left the EU – but that does not mean it has waived its environmental responsibilities with regard to the quality of the air breathed by its citizens. Indeed, it still respects the thresholds set out in those documents and the AURN is a key method of demonstrating that it continues to comply.

What are the Ambient Air Quality Directives?

The aforementioned Ambient Air Quality Directives were first established in 2008 to provide member states of the EU with the regulatory framework they needed to properly monitor and report on the air quality status of their nations.

As well as giving guidance on how data should be collected, organised and submitted, the Directives also delineate maximum “safe” thresholds for concentrations of a number of pollutants recognised as being potentially harmful to human and environmental health. These included sulphur dioxide, nitrogen dioxide, nitrogen oxides, particulate matter, lead, benzene and carbon monoxide.

Over the years, the Directives have been reviewed and redrafted to incorporate the latest data and recommendations supplied by bodies such as the United Nations and the WHO. The European Commission is planning its latest revision of the Directives currently and hopes to bring them into law by the end of this year.

What pollutants does the AURN measure?

The AURN is just one of several air quality monitoring networks in the UK and as such, does not cover the whole scope of pollutants listed by the Ambient Air Quality Directives. It is, however, the largest such network in operation in the country and presently encompasses the following five contaminants:

  • Nitrogen dioxide and nitrogen oxides (NO2 and NOx). Produced primarily by industrial sources and road transportation exhaust fumes, these are a chief cause of ambient pollution and can have deleterious effects for both humans and the ecosystems upon which they settle. Their ill-effects are most keenly experienced by humans in indoor settings.
  • Ozone (O3). Not to be confused with the beneficial layer of ozone which protects us from the sun’s UV radiation, tropospheric ozone is the main component of smog. It is produced when NOx or volatile organic compounds (VOCs) react with sunlight and it is known to cause or exacerbate respiratory conditions like asthma.
  • Sulphur dioxide (SO2). SO2 is produced naturally during volcanic eruptions, but its concentration levels have skyrocketed in recent years due to manmade sources of pollution such as smelting furnaces and other industrial process. In an environmental sense, it’s a precursor to acid rain, while it can also have health repercussions for humans and animals.
  • Carbon monoxide (CO). The biggest sources of CO are vehicle exhaust fumes and incomplete combustion of organic matter. Odourless and colourless, CO is known as the silent killer in non-ventilated spaces, where it can be deadly even in small concentrations. In outdoor environments, it’s more of a contributor to climate change.
  • Particulate pollution (PM10 and PM2.5). Widely considered as among the most damaging air pollutants to human health, PM10 and PM2.5 are tiny particles of pollution that can be inhaled into the lungs – the latter are so small they can even infiltrate the bloodstream. Once there, they can wreak untold damage on the internal organs of the person in question.

As mentioned above, there are other pollutants which the EU demands its member states monitor and report upon, including benzene, lead and polycyclic aromatic hydrocarbons (PAHs). However, the UK fulfils its commitments with regard to these via other air quality monitoring networks.

How is the AURN run?

As of February 2021, the AURN consisted of 171 monitoring stations across the UK. Although the exact techniques may vary from location to location and from contaminant to contaminant, they all employ state-of-the-art equipment and methods to ensure that standards are met when it comes to the quality and reliability of the data produced. They include such forward-thinking methods as UV absorption, UV fluorescence, chemiluminescence, IR absorption, gravimetric monitoring, beta attenuation monitoring, optical light scattering and several others.

The practicalities and logistics of the AURN are divided between several different organisations. At present, the Central Management and Coordinated Unit (CMCU) for the entire operation is handled by Bureau Veritas, while Quality Assurance and Quality Control (QA/QC) services are administered by the National Physical Laboratory in London and Ricardo Energy & Environment for the rest of the country. Individual sites are monitored and maintained by local organisations and individuals.

What is the data compiled by the AURN used for?

As well as being used to verify that the UK is complying with EU legislation, the AURN is also used to identify long-term meteorological patterns in the British climate and predict future developments. The data is also an excellent yardstick for assessing the effectiveness of current air pollution abatement policies and measuring whether or not progress has been made towards the government’s objectives.

What’s more, the fact that the AURN is a freely accessible service means that members of the general public can log onto it and see, at a glance, the various levels of different pollutants in their locality on any given day. This furnishes them with the information they need to make intelligent decisions about how to minimise their exposure to potentially dangerous contaminants in the air.


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