Ozone Pollution: Where, What and How

Ozone (O3), clarifyed by the United States Environmental Protection Agency (EPA), is a highly reactive gas composed of three oxygen atoms. It is both a natural and a man-made product that occurs in the Earth's upper atmosphere (the stratosphere) and lower atmosphere (the troposphere).

Source: drkazemipain.com

Where Does Ozone Comes From?

90% of ozone is found in the stratosphere and only 10% in the troposphere. 

In the stratosphere, ultraviolet radiation breaks the chemical bond between the two oxygen atoms of an oxygen molecule. Because oxygen atoms are so unstable, the remaining oxygen atom combines with another oxygen molecule to form ozone, a completely "natural" product.

Stratospheric ozone can absorb cosmic rays and ultraviolet-C radiation (UVC) emitted by the sun, and protect organisms on the earth's surface from damage. It can be called the "protective umbrella of earth's life".

However, most tropospheric ozone (ground-level ozone) is "man-made products", such as nitrogen oxides (NOx), volatile organic compounds (VOCs), etc., they are secondary pollutants produced by complex photochemical reactions.

Because of its strong oxidation, excessive concentration of ozone will have a series of adverse effects on human health. Ozone can strongly irritate the respiratory tract, causing airway response and aggravate airway inflammation, asthma and so on.

In addition, ground-level ozone can interfere with the structural integrity of the skin and the skin's barrier function, causing skin diseases, dark spots, and accelerated aging.

Source: healthline.com

Therefore, just as fine particulate matter (PM2.5) is the most important pollutant causing haze pollution, ozone is the primary pollutant of photochemical pollution, also known as tracer.

That is to say, excessive ozone occurred, indicating that there are other photochemical pollutants accompanied, especially some organic aerosols, which are also one of the main components of fine particles.

Source: semanticscholar.org

What Are the Harms of Ozone? 

High concentration of ozone has a great impact on human health, which can lead to the damage of central nervous system, lung function and thyroid function, tissue hypoxia, decreased visual acuity and visual sensitivity, chest tightness, cough, sore throat and aggravation of respiratory diseases.

A large number of epidemiological studies have shown that long-term ozone inhalation can increase the incidence and mortality of asthma and chronic obstructive pulmonary disease (COPD).

Ozone is very unstable and has strong oxidizing property. It also participates in many chemical reactions in the air and can react with many organic and inorganic substances, endangering indoor and outdoor materials, decorative coatings and cultural relics.

At the same time, these reactions will generate secondary pollutants, which contain a large number of aldehydes and are more irritating and harmful to human body and materials.

If the outdoor atmospheric ozone concentration is high, opening windows for ventilation or active ventilation of ventilation facilities will introduce ozone into the room.

Because there are many surfaces composed of indoor walls, furniture, living and office supplies, the ozone generally has a short life in the room. If there is no continuous source, the ozone will basically be consumed in a few minutes to several minutes.

However, if there is a continuous external source, the indoor ozone concentration will continue to increase. A more complicated and harmful problem is that there are some volatile organic compounds in the indoor environment that can react quickly with ozone.

Studies have shown that some indoor formaldehyde is the main product of ozone reaction with most indoor unsaturated hydrocarbons, and the reactants also include propionaldehyde, hexanal, propionic acid and hexanoic acid, as well as a small amount of acetaldehyde, valeraldehyde and nonanal.

Source: climatecentral.org

How to Protect Ourselves from Ozone Pollution?

Due to the strong chemical activity of ozone itself, it will decompose and oxidize most surfaces, but the decomposition rate depends on temperature, humidity, material contacted and residence time. Therefore, when outdoor ozone exceeds the standard, outdoor ventilation can be reduced and air purifier can be turned on.

A powerful air purifier can reduce the number and time of ozone contact with various surfaces. In particular, at present, many air purifiers are equipped with activated carbon filters, so the efficiency of reducing ozone concentration is higher.

However, it should also be noted that some high-voltage electrostatic purifiers will release ozone themselves. It should be ensured that the air purifier you use has an ozone filter screen or ozone-free function. 


It should be noted that even small amounts of ozone that do not exceed air quality standards are potentially harmful to human health.

Especially for people who work outside for several hours a day, even ozone concentrations below ambient air quality standards can negatively affect lung function.

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