Chemicals harmful to the atmosphereGo to:

What are substances that damage the atmosphere?subir

The release into the air of chemicals and particles can cause direct damage to the troposphere (air pollution); alter the composition and function of atmospheric layers (greenhouse effect) or other indirect damages (ozone layer depletion).

Air pollutants

An air pollutant is a substance in the air that can cause harm to humans and the environment. Indoor air pollution and urban air quality are listed as two of the world"s worst pollution problems in the 2008.

Pollutants can be classified as primary or secondary. Usually, primary pollutants are directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories. Secondary pollutants are not emitted directly. One example is ground-level ozone.

The transport sector has become one of the main emitters of polluting compounds in the world and one of the main causes of the greenhouse effect. Also, a report by the European Environment Agency (EEA) points out that road transport is the single largest air polluter in Europe. Through the burning of fuel, motor vehicles, cars and trucks emit a range of health damaging pollutants, such as particulate matter, nitrogen oxides, sulphur dioxide, carbon monoxides and Volatile Organic Compounds (VOCs). Some of the substances in motor vehicle exhaust also cause ‘secondary pollutants’ such as ozone, which are formed through chemical reactions in the air.

Air pollution is especially a problem in urban areas, where there is a lot of traffic. Some pollutants however can travel long distances and may accumulate in suburban or rural areas because of weather conditions such as wind or low pressure.

Compared with traffic, industrial activities are responsible for a larger total emission per year.

Main air pollutants are:

  • Sulphur oxides (SOx) – Mainly Sulphur dioxide (SO2). It is one of the causes for concern over the environmental impact of the use of fuels as power sources.

  • Nitrogen oxides (NOx) - NO2 is one of the most prominent air pollutants. Nitrogen (N) compounds, emitted as NOX and NH3, are now the principal acidifying components in our air and cause eutrophication of ecosystems.

  • Particulate matter - Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols.

  • Ozone (O3) - Ozone is not directly emitted into the atmosphere but formed from a chain of photochemical reactions following emissions of precursor gases: nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOC).

  • Carbon monoxide (CO) - It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.

  • Carbon dioxide (CO2) - emitted from sources such as combustion, cement production, and respiration.

  • Heavy metals, such as arsenic (As), cadmium (Cd), lead (Pb) and nickel (Ni)

  • Benzene and benzo(a)pyrene

  • Ammonia (NH3) - emitted from agricultural processes.

Other remarkable air pollutants that will be explained in separate chapters are:

  • Volatile organic compounds - VOCs are an important outdoor air pollutants

  • Chlorofluorocarbons (CFCs) - harmful to the ozone layer

Health impacts

Air pollution is a major environmental risk to health. Numerous scientific studies have linked air pollution to health effects including:

  • harm to the respiratory system, leading to the development or aggravation of respiratory diseases, decreased lung function, increased frequency and severity of respiratory symptoms such as coughing and difficulty breathing, or increased susceptibility to respiratory infections;

  • harm to the cardiovascular system;

  • harm to the nervous system, affecting learning, memory and behaviour;

  • harm to the reproductive system;

  • cancer

Some of these impacts may result in premature death. Sensitive individuals, such as older adults and children and people with pre-existing heart and lung diseases or diabetes, appear to be at greater risk of air pollution-related health effects.

Asthma and respiratory conditions are among the most common effects on human health and they raise especial concern in the case of children. 10% of European children suffer asthma, allergies and respiratory conditions associated with air pollution (particles).

In 2005, an estimated 5 million years of lost life were caused by fine particulate matter pollution (PM2.5) alone in the EEA-32 countries (EEA, 2010).

Ecosystem impacts

Air pollution also damages the environment. For example, ozone can damage crops and other vegetation, impairing growth. These impacts can reduce the ability of plants to take up CO2 from the atmosphere and indirectly affect entire ecosystems and the planet"s climate. The atmospheric deposition of sulphur and nitrogen compounds has acidifying effects on soils and freshwaters. Acidification causes disturbances in the function and structure of ecosystems with harmful ecological effects, including biodiversity loss. Likewise, deposition of nitrogen compounds can lead to eutrophication, which constitutes an oversupply of nutrient nitrogen in terrestrial and aquatic ecosystems. Consequences include changes in species diversity, invasions of new species and leaching of nitrate to groundwater.

Ozone-depleting substances

The stratosphere, a high layer of the atmosphere contains a high concentration of ozone. Ozone layer depletion allows a greater amount of ultraviolet (UV) radiation to reach the surface of the earth. An increase of UV radiation levels implies a significant harm to human health (skin cancer, cataracts, damage to the immune system) and to ecosystems, wild life and agriculture.

Some ozone-depleting substances are assigned with risk phrase R59 (according to DSD) and EU hazard statement system EUH059 (according to CLP): Hazardous to the ozone layer.

Greenhouse gases

Air pollution may also impact the Earth"s climate. Some air pollutants interfere with the Earth"s energy balance and are therefore known as "climate forcers".

These can either be gases (e.g. ozone) or airborne particulate matter (aerosols). Some climate forcers reflect solar radiation (e.g. sulphate aerosols) leading to net cooling, while others (e.g. black carbon aerosols) absorb solar radiation, thereby warming the atmosphere. In addition, aerosols influence the formation, microphysics and optical properties of clouds, resulting in indirect climatological effects.

Deposition of certain aerosols (e.g. black carbon) may also change the Earth"s surface reflectivity (albedo), especially on ice- and snow-covered surfaces, thereby accelerating melting.

The “greenhouse effect” is an increase of the average global temperature due to the accumulation of polluting gases in higher atmospheric levels that causes regional and global climate change.

The most visible greenhouse effects include:

  • increased frequency of extreme weather events (floods, draughts, retreating glaciers)

  • increase of sea level

  • extreme winter/ summer temperature differences

  • reduction of agricultural production in certain regions

  • alteration of natural systems

Climate change and ozone depletion are serious environmental problems that alter the stability of ecosystems and affect social structures.

What to do?subir

Avoid or reduce atmospheric emissions of these chemicals.

Outdoor air pollutants:

  • Request information on air pollutants emitted by the company.

  • Suggest the elimination or substitution of products or processes that generate those pollutants, replacing them with alternatives that eliminate or reduce air pollutants

  • When elimination or substitution is not possible, due to technical limitations, the second priority is to reduce the amount of air emissions, through plans to minimize the consumption of resources and raw materials and plans for minimizing emissions, discharges and waste generation, the reuse or recycling in situ, i.e. within the process or the introduction of best practices that reduce the risk inside and outside the facility, among other measures.

  • Control and monitor the company’s compliance with legal air emission requirements.

  • Promote saving and energy efficiency measures (e.g. knowledge of data on energy consumption, study facilities and equipment, identify opportunities for energy savings, opportunities for good practices for saving energy)

  • Promote sustainable mobility plans in companies to reduce the use of private motor vehicles (e.g. promotion of public transport access to the workplace, in coordination with the metropolitan transport authorities and transport companies, information for workers on daily mobility alternatives to private vehicles: on foot, by bicycle, public transport, car pooling, promotion of education for the mobility of workers to make them aware of the risks associated with current mobility model)

Ozone-depleting substances:

Request information from the employers about the use of ozone-depleting substances in the company

If ozone-depleting substances are contained in chemicals, processes or wastes control and follow-up measures must be adopted in order to:

  • Grant that these chemicals are not released into the atmosphere

  • Grant that wastes are handled adequately by an authorized agent specialized in this kind of activity

  • Substitute these chemicals for less dangerous products, equipment or processes

Chemicals that cause climate change:

  • Periodically request information on the emissions of chemicals that cause climate change

  • Propose to the company the development of studies, energy audits and energy efficiency plans with the participation of workers’ representatives

  • Put forward company mobility plans to reduce commuting in private motor vehicles

  • Propose the installation and use of renewable energies by the company


Ambient air quality

These substances do not have a specific classification at European level; however, is specific legislation to regulate these chemicals.

EU Directives 2008/50/EC of the European Parliament and of the Council on ambient air quality and cleaner air for Europe and 2002/3/EC of the European Parliament and of the Council relating to ozone in ambient air, establish information, protection and alert threshold values for these pollutants, although for some of them, like particles, there is no safety threshold. If the established limits are exceeded, authorities can suppress the polluting activities that prove significant for the risk situation.

Also, Regulation (EC) No 166/2006 concerning the establishment of a European Pollutant Release and Transfer Register (PRTR)’s annex II establishes a list of pollutants to air.

Ozone-depleting substances

The list includes substances of the Montreal Protocol on Substances that deplete the Ozone Layer.

Climate change

The list includes substances of the Kyoto Protocol to the United Nations Framework Convention on Climate Change

Related legislation and policies subir

Ambient air quality

  • Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe. Includes a list of air pollutants to be taken into account in the evaluation and management of air quality, determination of requirements for assessment of concentrations, limit values, registration target and alert thresholds for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter (PM10 and PM2,5), lead, benzene and carbon monoxide in ambient air within a zone or agglomeration.

  • Directive 2000/69/EC of the European Parliament and of the Council of 16 November 2000 relating to limit values for benzene and carbon monoxide in ambient air

  • Directive 2004/107/EC of the European Parliament and of the Council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air.

  • Directive 2001/81/EC of the European Parliament and of the Council of 23 October 2001 on national emission ceilings for certain atmospheric pollutants

  • Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions (Integrated Pollution Prevention and Control) (Recast)

  • Regulation (EC) No 166/2006   of the European Parliament and of the Council of 18 January 2006 concerning the establishment of a European Pollutant Release and Transfer Register and amending Council Directives 91/689/EEC and 96/61/EC.

Ozone layer

  • The Montreal Protocol on Substances that Deplete the Ozone Layer as adjusted and/or amended in London 1990, Copenhagen 1992, Vienna, 1995, Montreal, 1997, Beijing, 1999; Programme United Nations Environment Programme (UNEP) Ozone Secretariat.

  • Vienna Convention for the Protection of the Ozone Layer, United Nations Program for Environment (UNEP) Ozone Secretariat.

  • Regulation (EC) No 1005/2009 of the European Parliament and of the Council of 16 September 2009 on substances that deplete the ozone layer.

  • Directive 2002/3/EC of the European Parliament and of the Council of 12 February 2002 relating to ozone in ambient air.

  • Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe. Includes lists of data quality objectives for ambient air quality assessment, reference methods for assessment of concentrations, target values and long-term objectives, criteria for classifying and locating sampling points for assessments, criteria for determining the minimum number of sampling points for fixed measurement of concentrations and information and alert thresholds for ozone and related NO and NO2 (Annexes I, VI, VII, VIII, IX, XII) as well as measurements of ozone precursor substances (annex X),

Climate change

  • Kyoto Protocol to the United Nations Framework Convention on Climate Change

  • Directive 2003/87/EC of the European Parliament and of the Council of 13 October 2003 establishing a scheme for greenhouse gas emission allowance trading within the Community and amending Council Directive 96/61/EC

  • Directive 2009/29/EC of the European Parliament and of the Council of 23 April 2009 amending Directive 2003/87/EC so as to improve and extend the greenhouse gas emission allowance trading scheme of the Community


This list of air toxicants was developed from the following sources:

ListSourceDate of publication
Air qualityCouncil Directive 96/62/ECNovember 1996
Ozone layerRegulation (EC) No 1005/2009September 2009
Climate changeKyoto protocolJune 2005

Last updatesubir

July 2012


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