Energy Indicators for Sustainable Development: Guidelines and Methodologies International Atomic Energy Agency United Nations Department of Economic and Social Affairs International Energy Agency Eurostat European Environment Agency

ENV3: Air pollutant emissions from energy systems 
Brief Definition 
Emissions of air pollutants from all energy-related 
activities including electricity production and 
transportation. Main causes of growing concern are 
emissions of acidifying substances, such as sulphur 
oxides (SO
x
) and nitrogen oxides (NO
x
); ozone-
forming gases (ozone precursors), such as volatile 
organic compounds (VOCs), NO
x
and carbon 
monoxide (CO); and fine particulates 
Units 
Tonnes or 1000 tonnes 
Alternative Definitions 
Percentage change in emissions over time; 
emissions per unit of gross energy use 
Auxiliary Data/Indicators 
None 
Agenda 21 
Chapter 9: Protection of the atmosphere 
POLICY RELEVANCE 
(a) Purpose: This indicator tracks the release of air pollutants into the atmosphere 
from energy-related activities. It is used to evaluate the environmental performance of 
national policies and to describe the environmental pressure in relation to air pollution 
abatement in energy-related activities, including power generation and transportation. 
(b) Relevance to Sustainable Development: There is growing concern about higher 
concentrations of various air pollutants, mainly arising from energy use. The 
concentration of pollutants is largely influenced by energy production and 
consumption patterns, which in turn are affected by both energy intensity and 
efficiency. Emissions of these pollutants are also influenced by national standards of 
pollution abatement and control, and the use of clean energy technologies. The level 
of emissions gives an indication of the impact of human activities on the environment. 
A country’s efforts to abate air pollutant emissions are reflected in its national policies 
and international commitments. Concrete actions include structural changes in energy 
demand (efficiency improvements and fuel substitution) as well as pollution control 
policies and technical measures (e.g. the installation of industrial precipitators, 
denitrification and desulphurisation facilities, and the use of catalytic converters on 
cars). This indicator can therefore be used to assess environmental pressure in relation 
to energy production and use, and to evaluate the environmental performance of 
national policies designed to address four major impacts of air pollutants on health 
and the environment: 
• The acidification of soil and water by pollutants such as SO
x
and NO
x
. 
• The damage to buildings sensitive to these acidifying substances. 
• The formation of tropospheric ozone from so-called ozone precursors; for 
example, VOCs, NO
x
and CO, which indirectly affect human and animal 
health and vegetation. 

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• The direct effects on human health and ecosystems; for example, through high 
atmospheric concentrations of particulates and VOCs. 
Sulphur and nitrogen compounds are the source of environmental acidification. 
Anthropogenic nitrogen is predominantly emitted as NO
x
by transport sources, as well 
as by other energy uses and industrial processes. Airborne emissions of NO
x
contribute to both local pollution and to large-scale pollution through long-distance 
transport in the atmosphere. 
Air pollutants are associated with respiratory morbidity and mortality in humans; for 
example, NO
x
can irritate the lungs and lower resistance to respiratory infections. The 
effects of short-term exposure are still unclear, but continued or frequent exposure to 
concentrations higher than those normally found in the ambient air may cause 
increased incidence of acute respiratory disease. 
In the presence of sunlight, NO
x
react with VOCs to form tropospheric ozone and 
other oxidizing chemicals, which are toxic to living things, including human beings. 
NO
x
and sulphur dioxide (SO
2
) are also precursors to acids in rainwater and 
subsequently have deleterious effects on artefacts, aquatic organisms, agriculture and 
habitats. Atmospheric deposition of NO
x
can also contribute to eutrophication. In 
some areas, NO
x
are precursors to particulate matter concentrations. The deposition of 
nitrogen may be dry (in the form of gases and particles) or wet (in the form of rain or 
snow), or in the form of condensation (as fog and cloud droplets).