|In 1988 the Protocol concerning the Control of Emissions
of Nitrogen Oxides or their Transboundary Fluxes was adopted in Sofia
(Bulgaria). This Protocol requires as a first step, to freeze emissions
of nitrogen oxides or their transboundary fluxes. The general reference
year is 1987 (with the exception of the United States that chose to
relate its emission target to 1978).
Taking the sum of emissions of Parties to the NOx Protocol in 1994,
or a previous year, where no recent data are available, also a reduction
of 9% compared to 1987 can be noted. Nineteen of the 25 Parties
to the 1988 NOx Protocol have reached the target and stabilized
emissions at 1987 (or in the case of the United States 1978) levels
or reduced emissions below that level according to the latest emission
The second step to the NOx Protocol requires the application of
an effects-based approach. Applying the multi-pollutant, multi-effect
critical load approach, a new instrument being prepared at present
should provide for further reduction of emissions of nitrogen compounds,
including ammonia, and volatile organic compounds, in view of their
contribution to photochemical pollution, acidification and eutrophication,
and their effects on human health, the environment and materials,
by addressing all significant emission sources.
The collection of scientific and technical information as a basis
for a further reduction in nitrogen oxides and ammonia, considering
their acidifying as well as nitrifying effects, is under way.