Over the last decades, there has been much attention on air quality, especially in urban environments. A significant factor effecting the air quality in the urban environment is airborne particulate matter (PM). Long-term exposure to PM causes increased risk for heart disease, decreased lung function, exacerbation of asthma, and lung cancer. Therefore, many countries have implemented exposure limits to the concentration of ambient PM in the urban environments. The toxicity of PM is dependent on several factors such as chemical composition, shape, adsorbed materials, and particle sizes (usually divided in ultrafine, fine and coarse particles). However, the relationship between different PM properties and developing health hazards are not clear. Therefore, further studies to investigate different properties of PM may contribute to understanding the influence of PM on human health. 

In the present work, different novel methods to investigate sampled airborne PM and to investigate potential health effects have been used to increase the knowledge regarding street and wear particles. In study I, a sampling plan involving collecting one filter from Tapered Element Oscillating Microbalance (TEOM) monitoring stations used for Environmental monitoring each month for 20 months were developed. Particles on the filters were extracted into a suspension. TEOM particles were then studied with respect to constituents and variables that reflect their toxicity. The constituent and toxicity was found to be spatial and seasonal dependent. As a follow-up, in study II, TEOM filters from three geographical different cities were collected once a month for a year. The variation in particle mass measured with TEOM monitor, cadmium and lead contents, as well as endotoxin levels between locations and time points over the year was studied. The correlation between studied variables and biological effect was investigated. The results show that the concentration of metals and endotoxin in TEOM particles have no relationship to particle mass, while endotoxin levels coincided with pro-inflammatory response. These studies show that results from analyzing different variables on obtained particles from TEOM filters in combination with information about the ambient particle concentration, could be helpful in the evaluation of differences in the risk of breathing air at various locations. 

The dominant road traffic particle sources are wear particles from the road and tyre interface, and from vehicle brake pads. The particle concentrations are highest in cities with high traffic amounts and a high frequency of braking. There are a few cell studies that have investigated the toxicological and biological effect of these wear particles, but there is a lack of knowledge regarding their effect on tissue level. Furthermore, the knowledge about importance of rock materials in pavement is deficient. To mitigate these knowledge gaps, the effect of different wear particles from pavement and brake pad were tested using a model with isolated perfused rat lungs in study III. The wear particles from the pavement showed a significant decrease of tidal volume compared to unexposed controls. The largest effect were found with quartzite stone material. Wear particles from brakes instead showed a larger effect on released proinflammatory cytokines. The study shows that the toxic effect on lungs exposed to airborne particles can be investigated using repetitive measurements of tidal volume. Furthermore, the study shows that the choice of rock material in road pavements has the potential to affect the toxicity of road wear particles. This should be considered in environments where the concentrations and exposures are high. The brake particles showed a different effect than stone particles, indicating the need to differentiate wear particles from different sources in relation to health effects. In summary, the present work have investigated different aspects of airborne particles collected from streets as well as generated wear particles. These indicate different important aspects of the particles that may be of importance to better understand their health effects.