Background Street dust is composed of mineral particles from pavement wear and/or from traction sand that accumulate in the street during winter. In spring, when snow and ice melt and surfaces dry out, the particles become airborne and are a major source of urban air pollution (PM10) in sub-arctic regions (e.g. Scandinavia, the Baltic, North America and Japan). In Finland, it is considered to be one of the most problematic air pollutants, causing most of the high pollution episode days in urban areas. City residents are very aware of the street dust problem, which causes annoyance and health problems, especially for those who suffer from respiratory diseases. For this reason, the issue attracts considerable media attention. Although the Finnish municipalities have done much to mitigate street dust, these efforts were not enough to meet the limits required by the EU directive on ambient air quality and cleaner air for Europe (2008/50/EC). Although the Finnish municipalities have done much to mitigate street dust, these efforts have not been enough to meet the limits required by the EU directive on ambient air quality and cleaner air for Europe (2008/50/EC). Objectives The REDUST project aimed to: 1. Find best winter practices in the fields of traction control, dust suppression and street cleaning, and accelerate their implementation in order to reduce levels of respirable street dust (PM10) in urban areas (The project would demonstrate the emissions reduction potential and air quality benefits of these best practices. Associated costs would be estimated and compared with the current state.); and 2. Develop and implement a strategy to reduce levels of respirable (PM10) street dust by means of better winter maintenance practices in urban areas in Finland. Results The REDUST project demonstrated best practices to reduce PM10 street dust by means of winter maintenance. It carried out traction control practices (winter tyres, traction sanding), dust binding practices (dust binding solutions, dispersion techniques) and street cleaning practices (mechanical and vacuum sweepers, street scrubbers, combinations). These measures were shown to have the potential to significantly reduce street dust episodes and associated respiratory problems. During the project implementation, the number of days when respirable particles (PM10) exceeded the daily limit (>50 µg/m3) decreased in Helsinki’s city centre. Furthermore, the margin of particle levels exceeding the threshold on poor air quality days also declined, further indication that air quality is improving. The limit value was also not exceeded in Vantaa or Espoo. This declining trend is supported by both short- and long-term air quality measurements. Emission reductions and the costs of current as well as additional measures were calculated. Based on these calculations, an economically feasible street maintenance strategy was developed and implemented. The significant reduction in PM10 that occurred during the project is believed to be related to the improved strategic street maintenance actions. For example, the dust binding and street cleaning measures carried out on a 10 km Helsinki city route in spring 2014 led to a 15% reduction in PM10 dust emissions (~ 1 600 kg). The dust emission reduction is based on the estimation method devised by the project and is not an exact figure. The effectiveness of measures was expressed as percentage reductions in order to compare their relative efficiency when deployed on different streets in the participating cities. The project estimates that up to a 25% reduction in PM10 street dust emissions during spring can be achieved in busy urban traffic locations with improved dust binding and street cleaning actions. Communication activities were very important to the success of REDUST. Annual street dust seminars aimed at national expert were held during the four years of the project. Two international seminars were held for Scandinavian and Baltic audiences and the project experts attended in several international conferences and meetings to spread the project results to an even wider audience. The beneficiary has received significant interest from other cities in Finland. Investing in modern street scrubber may pose a challenge for smaller cities, but cooperation among cities and private contracting might reduce the financial burden on them. The best practices demonstrated have helped the city authorities to comply with the EU Directive 2008/50/EC on ambient air quality and cleaner air for Europe. Furthermore, the city of Helsinki has started to prepare a new air quality action plan (2017-2024), which will be completed in 2016. One of the aims of the plan is to reduce the risk of exceeding the PM10 limit value so the best practices demonstrated in REDUST will be included in the street dust section of the new air quality action plan, as they have been shown to be cost-effective means to reduce emissions of street dust. In the longer term, the city of Helsinki has adopted a new environmental policy where the aim is to reduce the annual maximum number of PM10 exceedances per year from 35 to 18 by year 2050. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).