Building our knowledge about air

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Article Published 15 Apr 2013 Last modified 11 May 2021
6 min read
Photo: © Gülcin Karadeniz
Our knowledge and understanding of air pollution is growing every year. We have an expanding network of monitoring stations reporting data on a wide range of air pollutants, complemented with results from air quality models. We now have to make sure that scientific knowledge and policy continue to develop hand in hand.

It is important to know what is happening in the city, the country and the world in which we live...

Bianca Tabacaru, Romania (ImaginAIR)

Mostly placed near busy roads in urban areas, or in public parks, air monitoring stations often go unnoticed. But these dull-looking boxes contain equipment that regularly samples the air at their location, measures exact concentration levels of key air pollutants such as ozone and particulate matter, and reports the data automatically to a database. In many cases, this information can be accessed online within minutes of the sampling.

Monitoring Europe’s air

Key air pollutants are addressed by European and national laws. For these pollutants, extensive monitoring networks have been set up across Europe to verify if the air quality at different locations complies with the different legal standards and health guidelines. These stations record and transmit measurements at various frequencies for a wide range of air pollutants, including sulphur dioxide, nitrogen dioxide, lead, ozone, particulate matter, carbon monoxide, benzene, volatile organic compounds, and polycyclic aromatic hydrocarbon.

The European Environment Agency brings together air quality measurements from more than 7 500 monitoring stations across Europe in the air-quality database AirBase. AirBase stores air quality data from previous years (historical data).

Some monitoring stations measure and report the latest data with a short delay (near real-time data). For example, in 2010, up to 2 000 stations were measuring ground‑level ozone concentrations continuously and reported the data every hour. Such near real‑time measurements can be used for warning and alert systems in the event of significant pollution incidents.

The number of monitoring stations across Europe grew considerably in the last decade, especially those that monitor certain key pollutants. In 2001, slightly more than 200 stations reported nitrogen dioxide measurements, whereas in 2010, close to 3 300 stations were reporting across 37 European countries. In the same period, the number of stations reporting PM10 almost tripled to reach more than 3 000 stations in 38 countries.

The growth of the monitoring network contributes to our knowledge and understanding of Europe’s air quality. Because setting up a new monitoring station with its high-tech equipment is quite costly, a part of our knowledge comes from other sources, such as satellite imagery; emission-estimates of large industrial facilities; air quality models; and in-depth studies on specific regions, sectors or pollutants.

Some 28 000 industrial facilities in 32 European countries report to E-PRTR — a Europe-wide pollutant registry — how much of various pollutants they release to water, land and air. All this information is online, and available to the public and policymakers alike.

Road transport

(c) Artens|Shutterstock

Compiling and accessing air-quality information

Putting together the information we gather from these various sources is challenging. The measurements by monitoring stations are location- and time-specific. Weather patterns, landscape characteristics, the time of the day or year, and the distance to emission sources all play a role in the pollutant measurements. In some cases such as road-side monitoring stations, a distance of even a few meters can have an impact on the readings.

Moreover, different methods are used to monitor and measure the same pollutant. Other factors also play a role. An increase in traffic circulation or traffic diversion schemes, for example, will result in different measurements than those recorded for the same street a year earlier.

Assessing the air quality of an area beyond the monitoring stations relies on modelling or a combination of modelling and measurements, including satellite observations. Air quality modelling often comes with some uncertainty, as models cannot reproduce all the complex factors linked to formation, dispersion and deposition of pollutants.

The uncertainty is much higher when it comes to assessing the health impacts of exposure to the pollutants at a given location. Monitoring stations usually measure the particulate matter mass per volume of air, but not necessarily the chemical composition of the particles. The emissions from car exhausts, for example, release black carbon containing particles directly into the air as well as gases such as nitrogen dioxide. But to be able to determine how public health might be affected, we need to know what the exact mixture in the air is.

Technology is instrumental in furthering our knowledge of the air we breathe. It is an essential element of the monitoring and reporting process. Recent developments in the information technology sector have enabled researchers and policymakers to process massive amounts of data in a matter of seconds. Many public authorities make this information accessible to the public, either through their websites, such as the municipality of Madrid, or through independent associations, such as Airparif for Paris and the broader Ile-de-France region.

The EEA maintains public information portals on air quality and air pollution. The historical air quality data stored in AirBase can be viewed on a map, filtered by pollutant and year, and can be downloaded.

Near real-time data (where available) on key pollutants such as PM10, ozone, nitrogen dioxide and sulphur dioxide can be accessed through the Eye on Earth AirWatch portal. Users can also add their personal ratings and observations to the viewing tool.

Higher quality analysis

Technology has not only enabled us to process larger amounts of data, it has also helped improve the quality and the accuracy of our analysis. We can now analyse at the same time weather information; road transport infrastructure; population density; and pollutant emissions from specific industrial facilities, along with measurements from monitoring stations, and outcomes from air quality models. For some regions, it is possible to compare premature deaths from cardiovascular and respiratory diseases to air pollution levels. We can plot most of these variables on a map of Europe and build more accurate models.

Air research is not only limited to the factors mentioned above. Marie-Eve Héroux from the World Health Organization’s Regional Office for Europe says, ‘The research community also looks into how various measures impact air pollution. There are very broad types of interventions from regulatory measures to changes in energy consumption patterns and sources, or changes in modes of transportation and the behaviour of people.’

Héroux adds, ‘All of this has been studied and the conclusions are clear: there are measures that can decrease pollution levels, particularly that of PM. It gives us an indication of how we can actually reduce death rates due to air pollution.’

A better understanding of health and the environmental impacts of air pollutants then feeds into the policy process. New pollutants, pollution sources and possible measures to combat pollution are identified and included in legislation. This might require the monitoring of new pollutants. The data collected as a result helps improve our knowledge further.

For example, in 2004, although there were measurements at the local and national levels, there was no monitoring station reporting directly to AirBase the concentrations of volatile organic compounds, heavy metals or polycyclic aromatic hydrocarbons in Europe. In 2010, there were more than 450, 750 and 550 such stations respectively.

ImaginAIR: Pollution in my city

(c) Bianca Tabacaru, ImaginAIR/EEA

A clearer picture emerges

Air legislation usually sets targets to be achieved in a given time frame. It also foresees ways to monitor progress and verify if the targets have been met within the expected timeframe.

For policy targets that were set a decade ago, two different pictures might emerge depending on the tools we use. The EEA looked at the National Emissions Ceilings Directive adopted in 2001, aimed at limiting emissions of four air pollutants by 2010, and assessed whether the eutrophication and acidification objectives stated in the directive were met.

Based on what we knew at the time the directive was adopted, the eutrophication objective appeared to have been met and the acidification risk appeared to have been reduced significantly. However, based on current knowledge using more up‑to-date tools, the picture is not as rosy. Eutrophication caused by air pollution is still a major environmental problem and there are many more areas that did not meet the acidification objective.

This year, the European Union is set to review its air policy, which will address new targets and a time frame that extends until 2020 and beyond. Along with its evolving policy on air, Europe will also continue to invest in its knowledge base.

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