This study monitored ultrafine particles (UFP) concurrent with environmental air quality data, investigating whether already existing instrumentation used by environmental authorities can provide reference values for estimating UFP concentrations. Of particular interest was the relation of UFP to PM10 (particulate matter) and nitrogen oxides (NOx, NO2) in ambient air. Existing PM measurement methods alone did not correspond exactly enough with the actual particle number, but we observed a link between NOx and NO2 to UFP concentration. The combined data could act as proxy-indicator for authorities in estimating particle number concentrations, but cannot replace UFP monitoring.