Urban concentrations of nitrogen oxides are frequently higher than in other areas and

near emission sources. There is often a steep gradient in NO2 concentration from the

roadside to the more general urban background. This gradient may be less pronounced

in heavily polluted areas and during episodes.

There are four recent large studies reviewing the air pollutant concentrations in

European cities: WHO study "Concern for Europe’s Tomorrow" (CET), RIVM/NILU

Study on Air Quality in Europe (the "Dobris Assessment") (Sluyter, ed., 1995), the

Auto-Oil study in 7 cities by the EC and the European Topic Centre on Air Quality,

MA2-4 project report “European Air Quality, 1993” (Larssen et al., 1995) .

In the WHO (CET study), a calculation of the urban population exposure to NO2 is

presented. NO2 concentrations from 144 cities in 18 European countries are available

for the late 1980s. The cities represent 91 million people, 29% of the European urban

population. The annual average concentrations of NO2 exceeded 60 Tg/m; for 19%

of the residents in these cities and 100 Tg/m; in one city with about one million

inhabitants.

 

 

 

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