Air Pollution by Ozone Across Europe

Episodic peak ozone levels in rural areas have been declining during the last three decades due to regional pollution emission controls applied to the VOC and NOx emissions from petrol-engined motor vehicles. Long-term downwards trends have been observed at many long-running rural monitoring stations in the EMEP ozone monitoring network. Downwards trends appear to be more pronounced at those stations where initial episodic peak levels were highest and insignificant at those stations where initial levels were lowest. This behaviour has been interpreted as resulting from the combined effect of regional pollution controls and increasing hemispheric ozone levels. Hemispheric ozone levels have been steadily rising in the northern hemisphere because of growing man-made emissions of tropospheric ozone precursors. Episodic ozone levels in major European towns and cities are rising towards the levels found in the rural areas surrounding them, as exhaust gas catalysts fitted to petrol-engined motor vehicles reduce the scavenging of ozone by chemical reaction with emitted nitric oxide.