United Nations Environment Programme

Print Version

Tool 5: Environmental Impacts

pollutionAir pollution does not only affect human health; it also has negative impacts on the natural environment. These impacts include: formation of ground-level ozone; acidification and eutrophication; and climate change.





 Photo: UNEP Still Pictures

Ground-level ozone:
Emissions of NOx and HC form ground-level ozone (O3), which is toxic to plants and damages crops and other vegetation, such as forests. Damage to crops from ground-level ozone has been shown to lead to reduced agricultural productivity.



Acidification and eutrophication:

Acidification and eutrophication (see glossary) may also cause damage to agriculture lands, forests, as well as to lakes, Acidification occurs when excessive amounts of sulphuric and nitric acid – which are formed from sulphur and NOx emissions released in the atmosphere – are deposited into the environment. Eutrophication, also called “nutrient pollution”, is caused partly by NOx emissions. However, the proportion of pollution from the transport sector is relatively minor, compared with other sources, such as phosphorous leakage from the agricultural sector. Resultant ecological effects from acidification and eutrophication include: reduced agricultural productivity; reduced aquatic life in lakes; excessive algae blooming in lakes; and “stressed” forests that either grow slowly or die altogether.

  • 10% of all land in the EU is estimated to be negatively affected by acidification, and over 20% of the land is negatively affected by eutrophication.

Climate change:
A long term – and perhaps the most serious –environmental effect from air pollution is climate change, which is characterized by rising average global temperatures. Tool 6 provides a more detailed explanation on how climate change works.

Average global temperatures have always shifted, and nature has an enormous capacity to adapt to these changes. Evolution of our ecosystems has generally occurred over thousands of years, giving ample time for animal and plant species to adapt and, if necessary, migrate to more suitable climatic zones


However, current changes in our climate are different than in the past. Most importantly, the rate of change is – from a climate systems perspective – extremely quick. The nature of these rapid effects from climate change are extremely complex, and therefore it is difficult – if not impossible – to fully understand them. Nonetheless, the majority of scientists, climate experts and governments agree that the effects of climate change will be severe and that action must be taken. Without enough time to adapt to the impacts of climate change, they will have serious detrimental effects on plant and animal life, as well as consequent negative impacts on virtually every economic sector.



Figure 3: Forest death and deteriorating historic buildings are two visible effects of acidification. Photos: UNEP Still Pictures