Not only exhaust fumes are toxic. AGH UST scientists investigate the pollution generated by road traffic

The photo shows several cars from behind, driving in a line on the road, and the cars are close to each other.

Exhaust fumes are not the only pollutants generated by cars. The research of AGH UST scientists shows that other health-threatening products include, for example, particulates from the wear of brake pads; photo by Dreamstime

Exhaust fumes are not the only pollutants generated by cars. Research by AGH UST scientists also demonstrates that other health-threatening products include, for example, particulates from the wear of brake pads. At the moment, they are investigating the exact input of road traffic into the overall air pollution in the area of Krasińskiego Avenue in Krakow.

When we think of air pollution related to road traffic, the first thing that pops into mind is the toxic products of fuel combustion. However, we should anticipate that with increasing numbers of low-emission cars, the problem will gradually lose its significance. Unfortunately, this doesn’t mean that we will soon be breathing fresh and clean air near our traffic-jammed roads. This is because the emission of particulate matter related to transport has sources also in, for example, road surface abrasion, wear of tyres, or degradation of road infrastructure. We might as well add the following to the list: the particulate matter from the corrosion of bodywork and the wear of the mechanical elements of the vehicle.

Dr hab. Ewa Adamiec – Professor at the AGH UST Faculty of Geology, Geophysics, and Environmental Protection – points to the threats stemming from the wear of brake pads: ‘On the one hand, technology strives to make these parts as durable as possible and to make them abstract as much heat as possible; and on the other hand, to be as cheap as possible. Therefore, many substitutes are used, which are of significantly worse quality. As a result, we have more and more particulates because the parts wear down. In the case of fuel combustion, investigations have been carried out since the 1970s, which brought about legislative work that introduced subsequent norms and limits. However, in terms of pollution originating from the wear of vehicle elements, there are no guidelines, and this creates huge risks’.

Not only exhaust fumes are toxic

The AGH UST Professor has conducted research on the particulate matter deposited on pavements near busy streets in Warsaw, Krakow, and Wrocław – Polish cities with the highest intensity of road traffic, as well as in Opole. The results are alarming. The analysis of the chemical composition of the particulates showed a very high contamination with many metals related to road transport, whereby antimony and copper may be directly linked to the brake systems of vehicles. What is particularly troubling is the fact that the investigation focused on the fine fraction (<20 µm) of dust, which is most easily resuspensed, i.e., it can be carried over and over by wind and air vortexes caused by moving vehicles. According to the most recent research, this process accounts for 50–70% of total particulate matter emissions from road transport. The concentration of elements in the samples analysed was so high that, according to the standards of the Environmental Protection Agency (EPA), their absorption by humans causes health risks, especially in the case of children.

Another similar investigation conducted by Professor Adamiec was related to particulate matter on cycle lanes near busy road junctions in the aforementioned cities. The research has not only expanded the previous findings, but also raised another issue. A detailed analysis of the forms of metals and their binding strength in the particulate matter demonstrated that, for instance, zinc and cadmium (to an even greater extent) are very mobile and can easily penetrate not only surface waters, groundwater, and soil, but also human organisms.

Checking what’s in the air

The ongoing research work, implemented within the framework of a university grant, carried out by Professor Adamiec and her interdisciplinary team “AGH dla Środowiska” [AGH UST for the Environment], aims to provide comprehensive information on the actual percentage of air pollution caused by road transport. To answer this question, the scientists study particulate matter collected near the roads in Węgrzce, Libertów, Giebułtów, and Niepołomice – towns surrounding Krakow – and from the capital city of Małopolska itself. The scholars take a particularily close look at the urban canyon that runs along Krasińskiego Avenue in Krakow. It’s probably an easy guess that this term refers to a place where the street is flanked by buildings with heights from several to, in this case, more than a dozen metres.

‘Ubran canyons are places where, under certain meteorological conditions, pollution is confined. This is why when we measure its concentration in communication stations, it’s relatively higher than in other ones. As far as the former are concerned, we’re dealing primarily with particulate matter pollution, in the case of the latter, we have the entire chemical processes that underlie the creation of secondary aerosols, when the pollution gets confined for extended periods. An important factor of this is also insolation, which can cause the photochemical creation of pollution’, explains Jakub Bartyzel, DSc from the Faculty of Physics and Applied Computer Science, who is responsible for the technical part of measurement data collection.

The scientists examine six various dust fractions ranging from 2.5 to 10 μm. Similarly to the previous investigations carried out by Professor Adamiec, they want to study the material in terms of its chemical and mineralogical compositions. They also intend to assess the health risks associated with that, taking the EPA standards as a benchmark. They also hope that their measurements will provide data on the spatial distribution of pollution in an urban canyon. As Dr Bartyzel points out, this is why the AGH UST scientists supplement the measurements taken by the station at the Krasińskiego Avenue with spot metering using an additional device that registers the fractional distribution of particulate matter in real time.

A model will show what influences the pollution

The measurements of air pollution concentration taken at various places of the street canyon are to validate mathematical models. The scholars want to use them to mirror the way in which changes in the structure of vehicles and traffic intensity have influenced the levels of pollution generated by road transport over the last decade. This is the period in which subsequent EURO norms have been introduced, which determine acceptable levels of exhaust fume emissions.

‘The fact that all model tests are quite uncertain, in our project, we had to limit ourselves to the urban canyon for which we have the Danish OSPM (the Operational Street Pollution Model) developed at Aarhus University. It allows us to recreate the concentration levels of selected contaminants, with about 20% accuracy, that have been registered by the air quality monitoring station. Having collected data on the scope of road transport emissions and background information on pollution and meteorological conditions, we can determine the extent to which road transport influences air quality’, describes Mateusz Rzeszutek, DSc from the Faculty of Mining Surveying and Environmental Engineering, who is responsible for tasks related to the modelling work.

Why are the data from the past decade so important to the scientists?: ‘The only proven method of improving air quality in cities is to reduce the emission of pollutants. This has always come at a cost to society. Consider the introduction of low-emission zones that will result in the need to replace older cars with newer models or will enforce the change of mode of transport in certain parts of the city. Therefore, we try to carefully analyse the historical data available to understand the influence of transport pollution levels on air quality in the past. This knowledge will allow us to predict more efficiently whether the actions planned in the area of air quality improvement bring about the desired results’, Dr Rzeszutek explains.

The project was funded by a university grant within the framework of the “Initiative for Excellence – Research University” project (the AGH UST 2020–2022, PRA-3).