Special feature: Easily understand air pollution

outdoor fireplace that gives off a big smoke synonymous with air pollution

Welcome to our comprehensive report on air pollution.

At R-PUR, we are convinced that a global understanding of air pollution would make it possible to change mentalities more quickly.

We are therefore keen to explain just what air pollution is, what causes it, and what you can do to protect yourself from it.

You can also discover our R-PUR anti-pollution mask solution to effectively protect you from air pollution.


In this comprehensive article, we'll explain simply how air pollution works, and you can click to read the section that interests you:

1. The composition of the air

2. The main air pollutants

3. Means of measuring air pollution in France

4. The ATMO index

5. The causes of air pollution

6. Natural causes of air pollution

7. The influence of meteorological conditions on air quality

8. The impact of air pollution on health

9. The impact of air pollution on the environment

10. Recommendations from the World Health Organization (WHO)

11. Solutions for better air quality

1. What is the air we breathe made of?

"Air" is the name we give to the mixture of gases that make up the Earth's atmosphere.

The composition, physical and chemical properties of air are very similar all over the world.

Our air is therefore a gaseous mixture mainly composed of 78% nitrogen (N2) and 21% oxygen (O2).

The remaining percentage is given a complex mixture of other gases such as carbon dioxide, helium and argon.

However, the air we breathe is never pure, since it is regularly polluted, largely by human activity but also by nature.

Update on how the air is polluted, measured, regulated, in France and around the world, and the dangers of its pollution for our health.

2. What are the main air pollutants?

There are two categories of air pollutants:

- primary pollutants, emitted directly: nitrogen monoxide, sulfur dioxide, carbon monoxide, particles (or dust), heavy metals, volatile organic compounds, polycyclic aromatic hydrocarbons...

It is therefore an air pollutant emitted directly by a given source.

- secondary pollutants resulting from physico-chemical transformations between air pollutants under the effect of particular meteorological conditions: ozone, nitrogen dioxide, particles)

This pollutant is therefore not emitted directly as such, but is formed when other pollutants (primary pollutants) react in the atmosphere.

What is a VOC (volatile organic compound)?

Many pollutants are identified by the acronym VOC, the best known is benzene. It is also the only regulated pollutant to date.

A VOC substance is a substance which is both defined by its composition (organic), and by its volatility (it can change from a solid state to a gaseous state under normal conditions of pressure and temperature).

Some 400 different types of volatile organic compounds can be found in the air today, and several thousand substances in commerce meet the definition of VOCs.

What about heavy metals?

Heavy metals are metallic elements present naturally in the environment, and used massively in industry.

This term is used when talking about air pollution because it can be found in the form of very fine dust and can be toxic in high concentrations.

To be more precise about their composition, in European law, they are defined as such:

“A heavy metal means any compound of antimony, arsenic, cadmium, hexavalent chromium, copper, lead, mercury, nickel, selenium, tellurium, thallium and tin, as well as these materials in metallic form, insofar as they are classified as dangerous substances. »

Now that we have listed the different pollutants that make up our air, let's see which ones are monitored and regulated, and how they are identified in France.

Multiple chimneys emitting air pollution smoke

3. How do we judge air quality in France?

The French territory is covered with networks of pollution measurement stations.

In total, there are 1,900 analyzers at 670 measurement stations.

An optimal pollution measurement is then ensured by mobile stations, or by direct investigations in the field.

These measurements will then be used by all the AASQAs, Approved Air Quality Monitoring Associations.

Approved by the State, they have strong expertise in the continuous monitoring of the air we breathe and in supporting the ecological transition with public and private actors as well as the general public.

Their missions can be summarized in four points:

  1. Monitor and predict pollution episodes.
  2. Inform and sensitize the population.
  3. Accompany decision-makers through actions.
  4. Improve knowledge on air pollution.

In France, we will therefore identify all these air pollution data and then judge their quality using the ATMO index.

4. What is the ATMO index?

The ATMO index is an index specific to France and was created in 1994. Its purpose is to measure air quality on a daily basis.

It identifies five regulated air pollutants: sulfur dioxide (SO2), nitrogen dioxide NO2, ozone 03 and particles with a diameter of less than 10 µm PM10, as well as 2.5 µm PM2.5.

This index qualifies the state of the air according to 6 classes: Good / Average / Degraded / Bad / Very bad / Extremely bad.

Each of these pollutants have varying characteristics.

sulfur dioxide SO2

Sulfur dioxide (SO2) is a gas, formerly called sulfur dioxide. It can also be found in liquefied form.

It is colorless, but has an acrid and pungent odor. Its inhalation is toxic and irritating to the respiratory system.

It is notably responsible for "acid rain" when combined with nitrogen dioxide.

Nitrogen dioxide NO2

Nitrogen dioxide (NO2) belongs to the family of nitrogen oxides, No.

It is easily recognizable since it is visible and smells. Indeed, it is recognized by its reddish-brown color and its characteristic acrid and pungent smell.

It is an odor that is typically found in streets polluted by automobile traffic.

Ozone O3

Ozone (O3) is the third gas in this index. It is pale and bluish in color, almost colorless. Its rather characteristic smell is reminiscent of bleach.

Emitted by industries and road traffic, it is the only pollutant currently on the rise in France and Europe.

PM10 fine particles

PM10 is particulate matter less than 10 microns in size and about six times thinner than a human hair.

Indeed, particulate matter or PM (Particulate Matter in English) is a physical particle: it is therefore defined by a size, unlike a gas.

PM2.5 fine particles

PM2.5 are fine particles with a size of less than 2.5 microns.

They observe each other with an entry-level microscope: their sizes are between a bacterium and a red blood cell .

We also observe PM2.5 is the smallest measured suspended physical particle of this index.

For more information, you can find our article dedicated to the air quality index , an essential tool for our health.

Now that we know which pollutants are identified by the ATMO index, let's now look at their origin.

5. What causes air pollution?

The first causes of air pollution are mainly anthropogenic: they are created by human activity.

The most polluting human activities are therefore:

Excessive burning of fossil fuels

    One of the main causes is the excessive combustion of fuels such as coal, oil and natural gas. This releases dangerous gases such as nitrogen oxides, carbon dioxide, and sulfur into the air. Domestic heating is a major contributor to this pollution, as well as automobile traffic and industries.

    Agricultural activities

      Agriculture is essential in France, but also has its negative aspects. The main sources of air pollution from agriculture are intensive animal husbandry, which produces methane (which leads to the production of ozone), as well as the burning of agricultural waste in the open air.

        6. What are the natural causes of air pollution?

        It may be surprising, but nature can also play a (sometimes important) role in the quality of outdoor air.

        Forest fires, volcanic eruptions, sandstorms, and certain weather conditions are all events that can also lead to pollution spikes.

        In France, pollution episodes are sometimes caused by dust blown from the Sahara desert. These dust episodes can be serious for a young child, an elderly person, a pregnant person or a person with a lung condition.

        Certain natural elements also, such as pollen, are not pollutants but will considerably influence air quality for a large part of the French population.

        Some factors of pollution are uncontrollable.

        But nature can just as much improve outdoor air quality, depending on different weather conditions.

        7. The influence of meteorological conditions on air quality.

        Weather and outside weather greatly affect air quality.

        So, when, for example, you want to practice outdoor sports, trusting the weather conditions can also be a good starting point:

        The influence of the sun on air quality

        The sun and hot weather are not allies for our health because they promote certain pollutants, such as Ozone.

        The reactions that create harmful ozone in our atmosphere require sunlight. In summer, and especially during extreme heat waves, ozone often reaches dangerous levels in cities, especially near major highways.

        man on the branch of a tree in the foreground with a city in the background

        The influence of cold on air quality

        When it's cold, we more distinctly perceive the smell of exhaust pipes and chimneys. Does this mean that this pollution is more present, or just more visible?

        The answer to this question is a bit of both. By a phenomenon of temperature inversion, the pollution will find itself "blocked" on the surface and will be more difficult to disperse.

        The cold therefore promotes air pollution.

        The influence of rain on air quality

        Rain , on the other hand, can have a positive, cleansing effect on air quality.

        Thus, the concentrations of polluting particles are much lower after heavy rains.

        The influence of wind on air quality

        The wind, on the other hand, is a double-edged sword. Winds can sweep pollutants and pollens out of an area and lower their concentrations, rapidly improving air quality.

        On the other hand, they can transport pollutants away from their sources, and lift dust to the ground, which impoverishes the quality of the outdoor air.

        8. What are the consequences today on our health?

        The numbers speak for themselves: air pollution kills 7 million people every year. In Europe, this would concern the premature death of 600,000 people each year.

        According to the WHO, air pollution has negative consequences on health, both in the short term and in the long term.

        In the short term, the effects of pollution on health are as follows:

        • Eye or respiratory tract irritation
        • Cough
        • Sore throat
        • asthma attacks
        • Increased risk of acute respiratory illnesses

          The long-term effects can be even more serious:

          • Cardiovascular accidents
          • A reduced life expectancy
          • COPD: chronic respiratory disease
          • lung cancer

          Pollution is not inevitable: in July 2020, the Energy Institute of the University of Chicago publishes a report on the loss of life expectancy due to air pollution.

          This study estimates that if all countries complied with WHO guidelines and recommendations, the life expectancy of all countries would increase by 2 years.

          It is also important to keep in mind that air pollution not only poses dangers to humans but also to our environment.

          You can find our complete file to easily understand the different respiratory diseases and their impact on your health.

          9. What is the impact of air pollution on the environment?

          Indeed, air pollution presents not only dangers for humans but also for our environment. And the list is not negligible: here are the main effects.

          Acid rains

          This phenomenon results in precipitation containing harmful amounts of nitric and sulfuric acids.

          These acids are formed primarily by nitrogen oxides and sulfur oxides released into the atmosphere during the combustion of fossil fuels.

          Dry haze or "smog"

          This subject is also dealt with in our dossier on NO2.

          This visual phenomenon obscures the clarity, the color, the shape of what we see. This phenomenon is similar to the effects of fog on a panorama, except that it is caused by pollution.


          Term that refers to the degradation of a body of water, too loaded with harmful substances such as nitrogen. This will stimulate the proliferation of algae and then cause the death of fish.

          This phenomenon, originally natural, is heavily accentuated by human activity.

          The degradation of the ozone layer

          Although at ground level ozone is a dangerous pollutant for humans, it forms a layer in the stratosphere that protects human life by preserving us from ultraviolet (UV) rays.

          Some man-made chemicals deplete this ozone layer every day.

          Deterioration of agriculture and forests

          UV radiation caused by ozone layer depletion, terrestrial ozone and acid rain can lead to reduced crop yields, and cause other environmental stresses such as increased susceptibility of trees to disease.

          Global warming

          This negative effect is the best known of all, and has serious repercussions such as rising sea levels which threaten coastal areas, the disappearance of hundreds of animal and plant species, agriculture, water resources, forests, and human health.

          Chimneys of large factories that emit air pollution and toxic smoke

          10. What are the recommendations of the World Health Organization (WHO)?

          In 2005, the WHO established guidelines, also called "information and recommendation threshold". This concerns air pollution and the limitation of pollutant emissions.

          The World Health Organization has conducted numerous studies showing that air pollution is a major environmental health problem affecting low, middle and high income countries alike.

          The 2005 WHO Air Quality Guidelines provide general recommendations on threshold values ​​for the main air pollutants that pose health risks.

          Thus, the limit values ​​to be observed for each of the main pollutants are as follows:

          • Fine particulate matter (PM2.5)

          10 μg/m 3 annual average
          25 μg/m 3 average over 24 hours

          • Coarse particulate matter (PM10)

          20 μg/m 3 annual average
          50 μg/m 3 average over 24 hours

          • Ozone (O3 )

          100 μg/m 3 average over 8 hours

          • Nitrogen dioxide (NO2)

          40 μg/m 3 annual average
          200 μg/m 3 hourly average

          • Sulfur dioxide (SO2)

          20 μg/m 3 average over 24 hours
          500 μg/m 3 average over 10 minutes

          *μg/m3: Micrograms per cubic meter

          The European Commission also plans to align its guidelines with WHO recommendations. As a reminder, air pollution still kills between 400,000 and 600,000 people each year in Europe.

          11. Solutions for better air quality

          In 2017, France released 164,000 tonnes of PM2.5 fine particles.

          She is far from being the best student in Europe.

          By changing our consumption habits quickly, France could meet the objectives set by the WHO, World Health Organization by 2030, which is far from currently being the case.

          We can all, at our level, contribute to clean air, and here are some actions to take on a daily basis:

          • Opt for low-consumption vehicles: as you will discover in our article on free-floating electric scooters, responsible solutions are gradually emerging.
          • Minimize car use by opting for carpooling and public transport.
          • Reduce the need for transportation at source by opting for telecommuting.
          • Prefer recycled products and opt for selective sorting.
          • Do not smoke indoors but outdoors, and especially away from young children or pregnant women.
          • Limit emissions from industrial chimneys.
          • Promote the use of renewable energy sources.

          Of course, improving air quality also depends on the actions taken by the responsible bodies, whether on a global scale (WHO), but also on a European (European Commission) and national (Ministry of environment, energy and the sea).

          The sources used to write this file

          Related to air pollution

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