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Main pollutants

2What are they?2

Human activities produce, use or handle numerous products likely to affect human health (depending on content and dosage). They are generated by a wide variety of activities – transport, heating, industry, agriculture, air conditioning etc.). Some of them have mostly local effects; atmospheric movements can also carry them very far and result in global effects (hole in the ozone, greenhouse effect, acid rain etc.)

Pollutant Sources Impact on health Impact on the environment
Sulphur dioxide (SO2) It is emitted during the combustion of fossil materials such as coal and fuel oils. The main sources are thermal power plants, large industrial combustion facilities and individual and collective heating units. The share of transport (diesel) reduces with the progressive elimination of sulphur in fuels. In the last fifteen years, SO2 emissions have dropped sharply, due to the technical and regulatory measures taken, the reduction in fuel oils and high-sulphur coal consumption and the emergence of nuclear energy. SO2 irritates mucous membranes, skin and the upper respiratory tract (cough, respiratory obstruction). It interacts with other substances, notably fine particles. As with all pollutants, its effects are exacerbated by smoking. SO2 turns into sulphuric acid when in contact with moisture and participates in the acid rain phenomenon. It also contributes to the deterioration of stone and the materials of many monuments.
Particles Most of the suspended particles or dust associated with human activity are generated by the combustion of fossil materials, car transport (exhaust gases, wear and tear, friction etc.) and various industrial activities (iron and steel industry, incineration etc.). Their size and composition vary dramatically. Particles are often combined with other pollutants such as SO2 or PAHs (Polycyclic Aromatic Hydrocarbons). PM10 represents the particle category whose diameter is lower than 10 micrometers. The diameter of PM2.5 or very fine particles is lower than 2.5 micrometers. Depending on their size (particle size distribution), particles penetrate more or less deeply into the lungs. The finer particles can, at relatively low concentrations, irritate the lower respiratory tract and affect respiratory function as a whole. Certain particles have mutagenic and carcinogenic properties. Fouling effects on buildings and monuments are the most obvious negative effects on the environment.
Nitrogen dioxide (NO2) The combination of nitrogen and oxygen in the air results in compounds with various chemical formulas grouped together under the term NOx. Regularly measured, nitrogen monoxide NO and nitrogen dioxide NO2 are emitted during combustion phenomena. NO2 is generated by NO oxidation. The main sources are transport (50%), industry (20%), agriculture (15%) and energy transformation (10%). Since 1993, catalytic converters have led to a drop in vehicle emissions but this effect remains limited in light of the sharp increase in traffic and vehicle replacement time. NO2 is also found in premises with gas appliances such as gas cookers, water heaters etc. NO2 irritates the bronchial tubes. It increases the frequency and seriousness of asthma attacks. It triggers pulmonary infections in children. NO2 contributes to the acid rain phenomenon, the formation of ground-level ozone, of which it is one of the precursors, the greenhouse effect and damage to the stratospheric ozone layer.
Ozone O3 In the stratosphere (altitude of 10 to 60 km), ozone O3 constitutes a natural filter protecting life on earth from the adverse action of “hard” ultraviolet radiation. The hole in the ozone is a partial disappearance of this filter, relating to the damaging effect of certain pollutants emitted into the troposphere and slowly migrating into the stratosphere. In the troposphere (from the ground up to 10 km), O3 level should be naturally low. This ozone is a secondary pollutant. It generally results from the chemical transformation of certain so-called primary pollutants (in particular NO2 and VOC), under the effect of solar radiation. Chemical mechanisms are complex and the highest O3 concentrations occur in the summer, on the outskirts of the areas emitting primary pollutants, and can then be carried over great distances. O3 is an aggressive gas easily penetrating the respiratory tract. It triggers coughs, lung problems as well as eye irritation. Its effects vary dramatically depending on the individual. O3 has an adverse effect on plant life (crop yield for example) and certain materials (rubber etc.). It contributes to the greenhouse effect and acid rain.
Volatile organic compounds (VOC) They are used in fuels as well as in many everyday products: paints, inks, glue, stain removers, cosmetics, solvents etc. for household, professional or industrial use (which is why their presence in internal air can also be significant). They are emitted during fuel combustion (notably in exhaust gases), or by evaporation during storage or use. VOCs are also emitted by the natural environment (Mediterranean vegetation, forests) and certain cultivated areas. VOC effects vary dramatically depending on the nature of the pollutant envisaged. They go from mild odour nuisance up to mutagenic and carcinogenic effects (benzene, certain PAHs), as well as various irritations and impaired respiratory capacity. VOCs play a role in the complex ozone formation mechanisms in the lower atmosphere. They are also involved in the processes leading to the formation of greenhouse gases and the hole in the ozone.
Carbon monoxide (CO) An odourless, colourless and flammable gas, carbon monoxide CO is the result of the incomplete combustion of organic materials (gas, coal, fuel oil, fuels, wood). The main source is motor vehicle traffic. High CO levels can be caused by an engine idling within a confined place or in a traffic jam in a covered area. The malfunction of household heating appliances can also result in high levels of CO in houses. CO adheres to haemoglobin in the blood instead of oxygen, leading to a lack of oxygen in the body (heart, brain etc.). Initial symptoms are headaches and dizziness. These symptoms get worse as CO concentration increases (nausea, vomiting etc.) and can lead to a coma and death in the case of prolonged exposure. CO contributes to ground-level ozone formation mechanisms. In the atmosphere, it turns into carbon dioxide CO2 and contributes to the greenhouse effect.
Toxic metals: lead (Pb), mercury (Hg), Cadmium (Cd), Nickel (Ni), zinc (Zn), manganese (Mn) etc. Toxic metals are generated by the combustion of coal, petroleum, household waste etc. as well as certain specific industrial processes. They are generally found in particles (with the exception of mercury, which is mostly gaseous). The widespread use of unleaded petrol has considerably helped reduce the concentration of this pollutant. Metals accumulate in the body and cause short and/or long-term toxic effects. They can affect the nervous system, kidney, liver and respiratory functions etc. Toxic metals contaminate soil and food. They accumulate in living organisms and disrupt biological balance and mechanisms. Certain lichens or foams are commonly used to monitor metals in the environment and serve as “bio-indicators”.
Ammonia (NH3) A mostly agricultural pollutant emitted when land spreading slurry from livestock farms but also when manufacturing ammonia fertilizers. It irritates the mucous membranes in the body.
Hydrogen sulphide (H2S) Easily recognisable by its rotten egg smell in very low concentration which disappears in higher concentrations. It is formed by anaerobic fermentation of organic substances.
Hydrochloric acid (HCl) Generated in particular by the incineration of household waste (containing plastic materials and paper rich in chlorine), coal combustion and certain industrial activities. This pollutant contributes to air acidification.
Polycyclic Aromatic Hydrocarbons (PAHs) Compounds made of 4 to 7 benzene rings. Several hundreds of compounds are generated by the combustion of fossil materials (notably by diesel engines) in gaseous or particulate form, the best-known being benzo(a)pyrene. The risk of cancer associated with PAHs has been known for some time.
Pesticides or plant protection products France is the world’s number two consumer of plant protection products. Large portions of these products miss their intended target and are emitted into the air, water etc. The first campaigns to measure pesticides in the air were carried out in Brittany in 1998. Only a few of the most frequently used molecules are monitored. New techniques are being looked into and validated. There is no existing air standard.


Law no. 96-1236 of 30 December 1996 on air and the rational use of energy. It is formalised in the environmental code, articles L220-1 and subsequent articles.

Order of 2 February 1998 relative to the water usage and consumption as well as all types of emissions of permit holding classified installations for environmental protection

Order of 10 December 2007 certifying laboratories or bodies to carry out certain types of sampling and analysis of substance emissions into the atmosphere