Stockholm used to have problematic levels of particulates (PM10) due to studded winter tires, but as of 2016 the levels are below limits, after street-specific bans. Instead the current (2016) problem is nitrogen oxides emitted by diesel vehicles. In 2016 the average levels for urban background (roof of Torkel Knutssonsgatan) were: NO2 11 μg/m3, NOx 14 μg/m3, PM10 12 μg/m3, PM2.5 4.9 μg/m3, soot 0.4 μg/m3, ultrafine particles 6200/cm3, CO 0.2 mg/m3, SO2 0.4 μg/m3, ozone 51 μg/m3. For urban street level (the densely trafficked Hornsgatan) the average levels were: NO2 43 μg/m3, NOx 104 μg/m3, PM10 23 μg/m3, PM2.5 5.9 μg/m3, soot 1.0 μg/m3, ultrafine particles 17100/cm3, CO 0.3 mg/m3, ozone 31 μg/m3.