A photo of the road, with passenger cars and buses. The visibility is hampered by street dust in the air.

Street dust is mainly made up of thoracic particles. Street dust has a large impact on air quality at breathing height. Street dust is generated as a result of road surfaces breaking down under tyres, grit pulverised into smaller particles and tyre and brake dust and dust from construction sites. 

Concentrations of street dust are at their highest in spring. There are occasionally high concentrations of dust also in the autumn and winter during the winter tyre season if the streets and roads are dry and there is no snow. Construction sites can create high concentrations of dust in their vicinity throughout the year.

During winter, particle masses gather on the street from various sources. This mass then is blown in the air due to traffic and wind after the streets have dried. Busy streets and roads have the largest concentrations of dust particles. The timing and intensity of the street dust season in spring varies every year according to the weather conditions.