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Ozone-forming emissions decreasing

Long-term progress:
Emissions of all compounds that form ozone in the troposphere have declined since 1990.
Short-term progress:
The decline in emissions seems to be continuing, despite the temporary slight increase due to the cold winter in 2010.
Progress in relation to targets:
EU Emission Ceilings Directive targets for 2010 were met for NMVOCs and nitrogen oxides.

Emissions of ozone precursors in 1990–2013

Emissions of ozone precursors
In the index calculated for emissions, the year 1990 = 100. In 1990, NMVOC emissions totalled 227 kilotonnes, CO emissions 622 kilotonnes, NOx emissions 286 kilotonnes and CH4 emissions 303 kilotonnes.
Sources: SYKE (NMVOC, CO ja NOx) and Statistics Finland (CH4). 2015

Air currents bring ozone to Finland from other parts of Europe

When present in the troposphere, the lowest layer of the atmosphere, ozone is an air pollutant harmful to human health. It also impairs plant growth. Ozone is useful in the upper atmosphere, because it absorbs harmful ultraviolet radiation coming from the sun, but very little ozone passes from the troposphere to the stratosphere.

Ozone is formed by the reaction of nitrogen oxides and hydrocarbons present in the air with sunlight. Transport, energy production and industry are the main sources of these. The generation of ozone, and its quantity and location are influenced by relative concentrations of various compounds and the amount of sunlight. The highest ozone concentrations in the lower atmosphere are typically found on the outskirts of cities and in rural areas, far from major emission sources.

The only way of reducing the amounts of tropospheric ozone is to lower emissions of the compounds that form it. Emissions of nitrogen oxides and non-methane volatile organic compounds (NMVOC) declined by almost one half in Finland, and those of carbon monoxide and methane by approximately one third, from 1990 to 2011.

Emission reduction in this country will not result in an immediate improvement of air quality here, because ozone is carried to Finland from other parts of Europe.


  • Finnish Environment Institute. 2015.


Published 2015-11-20 at 8:01, updated 2015-11-20 at 8:00