Mats Gustafsson

Properties and toxicological effects of particles from the interaction between tyres, road pavement and winter traction material

In regions where studded tyres and traction material are used during winter, e.g. the Nordic countries, northern part of USA, Canada, and Japan, mechanically generated particles from traffic are the main reason for high particle mass concentrations in busy street and road environments. In many Nordic municipalities the European environmental quality standard for inhalable particles (PM(10)) is exceeded due to these particles. In this study, particles from the wear of studded and studless friction tyres on two pavements and traction sanding were generated using a road simulator. The particles were characterized using particle sizers, Particle Induced X-Ray Emission Analysis and electron microscopy. Cell studies were conducted on particles sampled from the tests with studded tyres and compared with street environment, diesel exhaust and subway PM(10), respectively. The results show that in the road simulator, where resuspension is minimized, studded tyres produce tens of times more particles than friction tyres. Chemical analysis of the sampled particles shows that the generated wear particles consist almost entirely of minerals from the pavement stone material, but also that Sulfur is enriched for the submicron particles and that Zink is enriched for friction tyres for all particles sizes. The chemical data can be used for source identification and apportionment in urban aerosol studies. A mode of ultra-fine particles was also present and is hypothesised to originate in the tyres. Further, traction material properties affect PM(10) emission. The inflammatory potential of the particles from wear of pavements seems to depend on type of pavement and can be at least as potent as diesel exhaust particles. The results imply that there is a need and a good potential to reduce particle emission from pavement wear and winter time road and street operation by adjusting both studded tyre use as well as pavement and traction material properties.

The Policy Relevance of Wear Emissions from Road Transport, Now and in the Future—An International Workshop Report and Consensus Statement

Road transport emissions are a major contributor to ambient particulate matter concentrations and have been associated with adverse health effects. Therefore, these emissions are targeted through increasingly stringent European emission standards. These policies succeed in reducing exhaust emissions, but do not address “nonexhaust” emissions from brake wear, tire wear, road wear, and suspension in air of road dust. Is this a problem? To what extent do nonexhaust emissions contribute to ambient concentrations of PM10 or PM2.5? In the near future, wear emissions may dominate the remaining traffic-related PM10 emissions in Europe, mostly due to the steep decrease in PM exhaust emissions. This underlines the need to determine the relevance of the wear emissions as a contribution to the existing ambient PM concentrations, and the need to assess the health risks related to wear particles, which has not yet received much attention. During a workshop in 2011, available knowledge was reported and evaluated so as to draw conclusions on the relevance of traffic-related wear emissions for air quality policy development. On the basis of available evidence, which is briefly presented in this paper, it was concluded that nonexhaust emissions and in particular suspension in air of road dust are major contributors to exceedances at street locations of the PM10 air quality standards in various European cities. Furthermore, wear-related PM emissions that contain high concentrations of metals may (despite their limited contribution to the mass of nonexhaust emissions) cause significant health risks for the population, especially those living near intensely trafficked locations. To quantify the existing health risks, targeted research is required on wear emissions, their dispersion in urban areas, population exposure, and its effects on health. Such information will be crucial for environmental policymakers as an input for discussions on the need to develop control strategies. Implications: Road transport particulate matter (PM) emissions are associated with adverse health effects. Stringent policies succeed in reducing the exhaust PM emissions, but do not address “nonexhaust” emissions from brake wear, tire wear, road wear, and suspension in air of road dust. In the near future the nonexhaust emissions will dominate the road transport PM emissions. Based on the limited available evidence, it is argued that dedicated research is required on nonexhaust emissions and dispersion to urban areas from both an air quality and a public health perspective. The implicated message to regulators and policy makers is that road transport emissions continue to be an issue for health and air quality, despite the encouraging rapid decrease of tailpipe exhaust emissions. Supplemental Materials: Supplemental materials are available for this paper. Go to the publishers online edition of the Journal of the Air & Waste Management Association.

Spatial and temporal patterns of chloride deposition in southern Sweden

Monthly bulk deposition of chloride at 49 stations in Southern Sweden between 1989 and 1995 was used to produce quarterly and annual deposition maps through ordinary block kriging. Generally, deposition decreases from the west coast and eastward and displays a large annual variation, governed by the frequency and intensity of midlatitude cyclones. The 1st quarter dominates the temporal pattern all years except 1992. The 4th quarter is the second most important and the 2nd and 3rd quarters have generallylow deposition. The spatial deposition maximum was often displaced from the west coast to the western fringe of the South Swedish highland, due to orographic enhancement of precipitation. On the western rise of the highland, deposition almost entirely co-variates with precipitation. On the west coast and in the eastern part of Southern Sweden, thetemporal pattern is a more complex result of precipitation and frequency of strong westerlies. Comparing the quarterly total dataset with precipitation and frequency of westerly gales shows that both the 3rd and 4th quarters have higher mean precipitation than the 1st quarter, but lower deposition, while the second quarter has substantially lower precipitation but almost equal deposition to the 3rd quarter. The frequency of westerly gales shows a clearer, linear relationship to quarterly deposition. The 1st quarter has the highest variability in deposition and precipitation as well as in frequency of westerly gales. The importance of single highlysalt laden cyclones to the annual deposition is obvious in the 1st quarter of 1993. Changes in cyclone activity due to climate change is therefore of vital importance for the chemical characteristics of the midlatitude atmosphere.

Wear Particles from Studded Tires and Granite Pavement Induce Pro-inflammatory Alterations in Human Monocyte-Derived Macrophages : A Proteomic Study.

Airborne particulate matter is considered to be one of the environmental contributors to the mortality in cancer, respiratory, and cardiovascular diseases. For future preventive actions, it is of major concern to investigate the toxicity of defined groups of airborne particles and to clarify their pathways in biological tissues. To expand the knowledge beyond general inflammatory markers, this study examined the toxicoproteomic effects on human monocyte derived macrophages after exposure to wear particles generated from the interface of studded tires and a granite-containing pavement. As comparison, the effect of endotoxin was also investigated. The macrophage proteome was separated using two-dimensional gel electrophoresis. Detected proteins were quantified, and selected proteins were identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry. Among analyzed proteins, seven were significantly decreased and three were increased by exposure to wear particles as compared to unexposed control cells. Endotoxin exposure resulted in significant changes in the expression of six proteins: four decreased and two increased. For example, macrophage capping protein was significantly increased after wear particle exposure only, whereas calgizzarin and galectin-3 were increased by both wear particle and endotoxin exposure. Overall, proteins associated with inflammatory response were increased and proteins involved in cellular functions such as redox balance, anti-inflammatory response, and glycolysis were decreased. Investigating the effects of characterized wear particles on human macrophages with a toxicoproteomic approach has shown to be useful in the search for more detailed information about specific pathways and possible biological markers.

Prediction of Salt on Road Surface: Tool to Minimize Use of Salt

The competing goals of safety, accessibility, and environmental protection, together with limited funding, increase the need for cost-effective use of resources in the pursuit of winter maintenance activities. One way to minimize the amount of salt used in winter maintenance is to predict better the amount of residual salt on a road surface. This paper combines an empirical model developed in Sweden with data on residual salt, road surface wetness, and traffic from 18 Danish field case studies. The resulting model is presented as a mathematical function and in a graph. Decision makers might use such a model as a tool for understanding the durability of a dose of salt under various conditions (e.g., traffic, road surface wetness) and therefore minimize the amount of salt needed. The results of this study showed that the decay of residual salt could be modeled with traffic as an independent variable with a fair to quite good fit. Road surface wetness, as shown from the wheel tracks, related positively to the rate of residual salt loss. The wetter the surface, the faster the salt left the wheel tracks. On a wet road surface, the salt in the wheel tracks was almost gone after only a couple of hundred vehicles had traveled across the surface, whereas on a moist road surface, it would take a couple of thousand vehicles to reach the same result.

Review of Road Wear Emissions: A Review of Road Emission Measurement Studies: Identification of Gaps and Future Needs

Abstract Road wear is an important source for road dust and its emission into the air. Its contribution to particle emissions depends on the wear resistance of pavements as well as traffic characteristics. Especially in countries where studded tires are used, road wear can be a major factor for air quality deterioration. Therefore, most research on this matter has been performed in Nordic countries, to find ways of mitigating the road wear particle source. In this chapter, both experimental and field studies addressing source apportionment, particle physical and chemical properties, and factors affecting road wear emissions are reviewed. Finally, research gaps are identified and discussed.

Review of Road Dust Emissions

Abstract Non-exhaust emissions from road dust, such as particulate matter (PM) available for suspension from the road surface, can be a significant contributor to traffic-related PM emissions. The sources of road dust can be many and varied and include traffic-related wear of roads, tires, and brakes, as well as a range of other sources, such as traction sanding, road salt, atmospheric deposition, migration, or entrainment from roadside dust or construction sites. The contributions vary depending on location, tire types, road surface quality, etc. Processes affecting road dust loading and emission include traffic suspension rates, driving patterns, road drainage, and vehicle spray. Importantly, meteorological conditions, such as road surface wetness, have a strong controlling impact on road dust retainment and suspension. As vehicle and road wear sources, often referred to as being direct emissions, can also be deposited on the road surface to become road dust, care should be taken in describing these sources, to avoid any double counting.