The UN ECE Convention on Long-Range Transboundary Air Pollution (LRTAP
) has decided on reduction of transboundary air pollution in three pro
tocols; one on sulphur, nitrogen oxides and volatile organic compounds
(VOCs) respectively. These protocols are not sufficient to solve the
air-pollution problem in Europe. Further reductions and agreements are
necessary to achieve sustainable ecosystems. In further negotiations,
which should be based on critical loads, it is important to consider
that the regional air-pollution problem consists of a complicated matr
ix of compounds and effects. Thus, control of one problem will influen
ce other problems, and control of one compound will affect the transpo
rt and effects of others. This is certainly the case for nitrogen oxid
es (NO(x)), which play an important role in acidification and eutrophi
cation effects as well as in the formation of photochemical oxidants.
This article discusses the scientific rationale for considering effect
s and their precursors together. Variations in effects and their cause
s are discussed and suggestions for a different approach to the future
control of regional air pollution are given.