Document Actions - Published:
20 Jul 2009 - Ground-level ozone is among
the most harmful air pollutants in Europe
today. Elevated ozone levels cause health
problems, premature deaths, reduced agricultural
crop yields, damage to plants in semi-natural
ecosystems and
corrosion of physical infrastructure and
cultural heritage.
Troublingly, efforts
to combat European ozone levels are achieving
only limited success. Although Europe has
steadily reduced emissions of the air pollutants
that lead to ozone formation in recent decades,
ozone levels remain largely unchanged in
many countries.
A new report by the
European Environment Agency (EEA), released
today, explores the reasons for this apparent
contradiction, using data from the European
air quality database, AirBase, and computer
models to investigate ground-level ozone
formation in Europe.
Key findings
The longest time series in AirBase (14–16
years) are available for four countries.
These indicate that ground-level ozone has
declined significantly in the Netherlands
and the United Kingdom, falling during the
11000s and leveling off thereafter. No significant
trends were identified in Austria and Switzerland.
Inter-annual variations
in weather conditions have a significant
impact on yearly ozone levels. Discerning
the effect of reduced ozone precursor emissions
therefore requires long time series of data
from stable monitoring networks. Unfortunately,
extended time series are generally unavailable,
particularly in southern Europe where ozone
pollution is a major problem.
Several unknowns complicate
attempts to model ozone levels. Significant
uncertainties exist regarding the magnitude
and distribution of inter-continental inflows
of ozone and its precursors, and the size
and distribution of isoprene emissions from
plants.
The importance of meteorological
conditions in ozone formation suggests that
predicted changes in climate could also
lead to increased ground-level ozone in
many regions of Europe.
Computer modelling was
used to estimate the ozone levels that would
arise if precursor emissions declined (as
countries reported) or if they held constant
at 1995 levels. The ozone levels recorded
in 18 countries across Europe correspond
more closely to the model output based on
the assumption of declining emissions.
Ground-level ozone has
become a hemispheric or even global air
pollution and climate change problem. Ozone
abatement should be integrated into local,
regional and global strategies and measures
that simultaneously address emissions of
air pollutants and greenhouse gases.
