2023-07-27 10:17:05
Ozone is a pollutant. It is necessary to protect oneself when the authorities announce a pic de pollution. You will then have to give up your physical activities outdoors…
Definition: what is ozone (O3)?
L’ozone is a gas with a very oxidizing power present on the surface of the ground (between 0 and 12 km above the ground) and made up of three oxygen atoms (O3).
We are interested in ozone when we seek to assess the outdoor air pollution level. Indeed, when it is present in too high a concentration, ozone can have harmful effects for human health but also for ecosystems.
Sometimes we talk regarding the famous “ ozone layer », a protective layer located more or less 20 km above sea level. It has a high concentration of ozone, which then acts as a protective filter once morest the aggressiveness of ultraviolet rays. THE hole in the ozone layer, which appeared in the early 1980s, has become a seasonal phenomenon linked to air pollution. It results in a significant decrease in the thickness of the ozone layer above the poles, during the spring of each hemisphere.
What is ozone used for?
Ozone is an air pollutant on the surface of the ground but it is also a constituent of the ozone layer located at high altitudes. This layer formed by ozone has a great utility: it protects us from a overexposure to ultraviolet radiation (especially UVB and UVC) harmful to human health (risk of cataracts, skin cancer, weakening of the immune system, etc.) and plants (inhibition of the photosynthetic activity of plants).
Human activities are the main factor responsible for thethinning of the ozone layer (or hole in the ozone layer), mainly due to emissions into the atmosphere of synthetic chemicals.
Why is ozone a pollutant?
The ozone present on the surface of the ground (in the lower layers of the atmosphere which therefore concern us directly) is formed under the action of UV solar radiation on hot days and in the presence of significant concentrations ofnitrogen oxideof volatile organic compounds (including the methane) or even carbon monoxide. All of these products are pollutants emanating from human activity.
As you have understood, ozone is indeed a polluting gas. And for good reason, it even has a acrid smell (the word “ozone” comes from the Greek “ozein” and means “to feel”). One can sometimes smell ozone when it is present in high concentration, particularly in unventilated rooms containing (old) photocopiers, or, outdoors, following a storm characterized by strong electrical activity (source 1). In large quantities, ozone is even noticeable: it has a bluish color.
What is the concentration of ozone in the air?
The ozone concentration in the air depends on weather situation and polluting human activity. Ozone increases especially in the summer period and can even reach alert thresholds in the summer period. heat wavemost recently during the summers of 2018 and 2019 for example (source 2).
- Below 120 µg/m³, we consider ozone content as harmless and the optimal air quality.
- Between 120 and 150 µg/m³: “significant pollution”. The level of this ozone pollution has an impact especially on people who already suffer from pulmonary and cardiovascular diseases, on children and on the elderly.
- Between 150 and 180 µg/m³: “marked pollution”. We then speak of a pollution episode or peak. Sensitive people will probably suffer from irritation of the mucous membranes (eyes, nose, throat).
- Between 180 and 240 µg/m³: “high pollution”. We are talking regarding ozone pollution peak. There is an increased likelihood of mucosal irritations.
- Above 240 µg/m³: “very high pollution”. The probability of irritation of the mucous membranes even in healthy people is greatly increased.
How to monitor day-to-day air quality in France?
In France, the Prev’Air platform offers a carte showing the concentration of ozone in the air from day to day. This site allows you to anticipate what to do in the event of a pollution peak.
Causes: what emits ozone?
The main ozone precursor gases are nitrogen oxide, volatile organic compounds (including methane) and carbon monoxide (the latter is present in smaller quantities). The latter are emanations from our human activities (road traffic, industrial, agricultural and domestic activity, residential heating, use of solvents, etc.) and from vegetation (cultivated or uncultivated plant species and soils) under the effect of solar UV radiation.
Symptoms: what are the effects of ozone on health?
A spike in ozone pollution can cause various symptoms such as:
- a nose and throat irritation ;
- a cough ;
- pain during deep inspirations;
- a decreased respiratory function and some lung capacity ;
- of the difficulty breathing during physical exertion and outdoor sports activities;
- of the asthma attacks (especially in people with asthma);
- accentuation of the reaction of the respiratory tract to other irritating substances (fine dust, nitrogen dioxide, pollen and dust mites).
Consequences: what are the risks of ozone on health?
Ozone is one of the gaz irritants the most powerful. In humans, it mainly attacks the respiratory tract and lung tissue. The health risk depends on its concentration in the air, the duration of exposure and the physical effort exerted. In the long term, this pollutant is notably responsible forworsening of diseases of the respiratory system which can lead to hospitalizations and to many deaths (source 3).
Ozone peak alert: what to do? how to protect yourself?
In case of strong ozone pollution, it is recommended to:
- going out preferably before 11 a.m. and following 8 p.m. (so avoid going out in the followingnoon);
- do not engage in strenuous outdoor physical and sporting activities;
- avoiding activities that may cause shortness of breath (i.e. breathing through the mouth);
- monitor the appearance of respiratory discomfort (asthma or suggestive symptoms: fatigue, stuffy nose, cough, shortness of breath, wheezing, palpitations, etc.). In the event of respiratory discomfort or cardiac symptoms, make an appointment with your attending physician without delay;
- continue to ventilate your home twice 10 minutes a dayr, preferably on the courtyard side and early in the morning in winter or at night in summer.
- do not stop ventilation.
Air pollution, the new public enemy number 1 of health?
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