In the stratosphere (between 10 and 60 km in altitude), ozone (O3) is a natural filter that protects life on earth from the harmful (ultraviolet) rays of the sun . The "ozone hole" is a partial disappearance of this filter, linked to the ozone destroying effects of certain pollutants emitted into the troposphere and that move slowly into the stratosphere.
In the troposphere (between the ground and 10 km in altitude) O3 concentrations should naturally be low. This ozone is a pollutant termed "secondary". It is usually the result of the chemical transformation in the atmosphere of certain pollutants known as "primary" (in particular NOx and VOCs), under the influence of solar radiation. The reaction mechanisms are complex and the highest concentrations of O3 appear in summer, on the outskirts of areas emitting primary pollutants, and the ozone can then be transported long distances.
O3 is an aggressive gas that easily penetrates to the smallest respiratory airways. It causes coughing, impaired lung function as well as irritation of the eyes. Its effects vary depending on the individual.
Effects on the environment
O3 has a negative effect on vegetation (on crop yields, for example) and on some materials (rubber. ..). It contributes to the greenhouse effect and to acid rain.
The reference standards
Information and recommendation threshold for sensitive individuals
Alert warning threshold for the general population
Atmo Normandie is an association for monitoring air quality.It belongs to the national organization , is member of ATMO France Federation and approved by the French ministry for ecology.
Among its missions : providing measurement, expertise, advice and information.