What are the sources of particulate matter? TOPAS shows us

21 March 2019 • 3 min reading time

Air quality in the Netherlands is improving. Yet, air pollution is still responsible for around 12,000 premature deaths in this country every year. Particulate matter is the main culprit. Thus, it is important to trace the places of origin of particulate matter. We now have the tools to do the job.

Care to know more?

Would you like to know more about TOPAS? If so, please contact Martijn Schaap.


Smoking is the main cause of disease in this country. Inhaling cigarette smoke is responsible for 13% of the disease burden. So what is in the number 2 spot? No, it’s not overweight (5%) or lack of exercise (3% to 4%). Second place goes to environmental factors (6%), with particulate matter alone accounting for around 4% of the disease burden. So it’s not surprising that, in 2018, the Health Council of the Netherlands advised the government to take extra measures aimed at drastically reducing particulate matter levels.

“Until now, it has always been difficult to pinpoint the exact place of origin of local air pollution”

Major sources of particulate matter

Particulate matter is generated by the combustion of fuels, by wear and tear, and by the processing of materials. Agriculture and motorized road traffic are major sources of particulate matter, as are shipping and industry. That’s a fact. The only problem is that it has always been difficult to pinpoint the exact place of origin of local air pollution. This is not made any easier by the fact that almost half of all the particulate matter in the Netherlands comes from other countries. Then there are natural sources of particulate matter, such as the sea (sea salt) and the Sahara desert (sand).

Do the maths

Locating the places of origin of particulate matter is no simple matter; you need an incredible amount of information. To begin with, you must have comprehensive data on road traffic, shipping traffic, agricultural areas and industrial areas – including details of the associated emissions. You also need accurate weather data, as input for the underlying air quality model. Also, you will need a powerful computer and modern calculation techniques to calculate the source apportionment.

“TOPAS is a web application that provides up-to-date information on the places of origin of particulate matter in over 200 European cities”

Web application

Despite the difficulties involved TNO accepted the challenge and developed TOPAS. “TOPAS is a web application that provides up-to-date information on the places of origin of particulate matter in over 200 European cities, in addition to identifying the types of sources involved” This is still the beta version of the app, so policymakers and other interested parties can use it free of charge.

No more guess work

“Before you can formulate an effective air quality policy, you need to identify the sources responsible for particulate matter concentrations in a given area. Until recently, it has always been difficult for policymakers to get a reliable picture of what was going on, especially on smoggy days. TOPAS has given us a reliable and easily accessible way of understanding the source apportionment of particulate matter”, says Martijn Schaap, the TNO researcher who – together with his team – was behind the development of this web application.

“We want to rapidly make use of the data that TROPOMI generates as it orbits the Earth”

Even more accurate

“As yet, the application does not identify a precise location, only the country of origin”, Dr Schaap adds. “We want to fine-tune that down to the level of individual counties or provinces, for example. “We want to rapidly make use of the data that TROPOMI (the TROPOspheric Monitoring instrument) generates as it orbits the Earth”. With the aid of artificial intelligence, it will then be possible to identify emission sources more accurately then ever before. It will also enable us to accurately indicate their contribution to the total emissions of particulate matter and other air pollutants.

International cooperation

There is already a lot of interest in TOPAS. This has led, for example, to a strategic partnership with the Freie Universität Berlin, where Schaap is currently also working as a part-time professor. TNO also cooperates closely with national and European partners in the field of particulate matter research. It also recently launched a cooperative venture with the Croatian Meteorological and Hydrological Service. It would appear, therefore, that there is a clear need for TOPAS. Never before have we had such a detailed understanding of particulate matter. And this is just the beginning.

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