Dispersion and exposure calculation of PM10, NO2 and benzene for Oslo and Trondheim for the year 2005.

Commissioned by the Norwegian Pollution Control Authority (SFT), NILU has performed dispersion and exposure calculations for PM10, NO2 and benzene (C6H6) for the year 2005 for the two Norwegian cities Oslo and Trondheim. The number of inhabitants exposed to exceedances of the National Air Quality Target for the three compounds have been computed both in building points and in the model grid squares. The calculations show that 0.12 %, 44.8 %, and 6.0 % of the Oslo population are exposed to exceedances of the National air quality target for NO2 , PM10 , and benzene, respectively. The corresponding numbers for Trondheim are, 0.026 %, 13.8 %, and 0 %. The calculations of the percentual contributions from the various sources demonstrate that road traffic is the dominant source to the exceedances of the national target for both NO2 and PM10. For PM10 domestic wood combustion is clearly the second most dominant local source. No calculations of source contributions has been made for benzene, but earlier investigations (Laupsa et al., 2005 a) have shown that raod traffic is by far the most dominant source for the exceedances with regards to this compound as well.