The Swedish Urban Air Quality Network — a cost efficient long-term program

The Swedish Urban Air Quality Network was established in 1986 as a joint project between the Swedish Environmental Research Institute (IVL) and the local health departments in Swedish towns. Within the network, air pollution measurements are carried out every winter season (October–March) at one site in town centre, where concentrations are expected to be highest but without direct influence from local sources. Starting with SO2, soot (black smoke) and NO2, taken as daily means, the program was later expanded and includes now volatile organic compounds (VOC) as weekly means, and SO2 and NO2 at two places in the countryside nearby some of the towns, taken as monthly means. The main purpose with the project is to study long-term changes in the air quality and to determine the contribution from local and regional sources as well as from long-range transport. In addition, the influence from latitude, size of the city, number of inhabitants, local traffic, local heating and industries on the concentrations is investigated. Over a nine-year period a clear downward trend is observed in SO2 and NO2 concentrations. For soot no consistent trend is found.