Many times, when we go out into the street, we can observe a kind of smoke in the air, which we mistakenly identify as fog. This phenomenon is known as smog, specifically, the photochemical smog.
Smog is a type of atmospheric pollution which can negatively affect both the environment and our health. In this article, we will explore in detail what smog is, how it is produced, its consequences and possible solutions to combat it.
What is smog?
El smog It is a mixture of smoke and fog that occurs in the atmosphere due to the accumulation of pollutants. Its name comes from the English words smoke (smoke) and fog (fog). Although most visible in large cities, smog can affect any area with high levels of pollution.
There are two main types of smog:
- Photochemical smog: Caused by the interaction of sunlight with nitrogen oxides and volatile organic compounds.
- Sulfurous smog: Generated primarily by coal burning and sulfur emissions, this type of smog typically occurs in industrial areas or areas with cold climates.
How is photochemical smog produced?
El photochemical smog It is formed when primary pollutants present in the atmosphere, such as nitrogen oxides (NOX) and volatile organic compounds (VOCs), react under sunlight. These primary pollutants are released mainly through emissions from vehicles, factories and power plants.
The main reactions that occur are the following:
- Nitrogen oxides (NOx) break down in sunlight, releasing more oxygen that reacts with other pollutants.
- Tropospheric ozone, known as bad ozone, is produced and becomes the most dangerous component of photochemical smog.
- VOCs, when mixed with ozone, also generate harmful compounds such as peroxyacyl nitrate (PAN).
This reaction is favored by a high solar radiation, so the highest levels of photochemical smog usually occur in summer and during the central hours of the day.
Consequences of photochemical smog on the environment
Photochemical smog has a significant environmental impact, affecting vegetation, water bodies and wildlife.
- Reduced Visibility: Smog drastically limits visibility, creating a dense layer that prevents seeing the horizon and even the sky.
- Impact on vegetation: Tropospheric ozone damages the leaves of trees and plants, slows their growth and reduces their photosynthetic capacity.
- Global warming: Although smog creates a barrier that blocks some of the sunlight, it also acts as a greenhouse that captures heat in the lower layers of the atmosphere.
- Alteration of the water cycle: Suspended particles can reduce rainfall by disrupting natural rainfall patterns.
In some highly polluted cities, such as Beijing or Mexico City, pollution levels are so high that smog clouds can last for weeks, making all these impacts worse.
Health consequences of photochemical smog
Smog puts people's health at risk, especially those with respiratory and cardiovascular problems.
- Eye and respiratory tract irritation: Ozone and other pollutants can cause coughing, sore throat and red eyes.
- Worsening of chronic diseases: Those who suffer from asthma, bronchitis or emphysema will see their symptoms worsen.
- Lack of oxygen: High levels of carbon monoxide (CO) can make it difficult for oxygen to be exchanged in the lungs, mainly affecting older people or those with lung deficiencies.
- Early death: In severe and prolonged cases, exposure to smog can lead to premature death, as demonstrated by disasters such as the "Great Smog" in London in 1952, which killed thousands of people.
Cities with the highest level of smog
Some cities are more prone to high levels of smog, especially those that lack natural sources of air renewal, such as wind or rain. These factors, combined with high levels of pollution, create the perfect conditions for smog to build up.
- The Angels: Surrounded by mountains and suffering from prolonged temperature inversions, the city is almost synonymous with smog.
- Mexico City and Santiago de Chile: Located in valleys, they lack winds strong enough to dissipate pollutants.
- Beijing: The massive use of coal and vehicles makes this city one of the most polluted in the world almost all year round.
Solutions to combat smog
La fight against smog must be addressed from different fronts. Not only governments, but also large corporations and citizens must take action. Here are some main approaches:
- Government policies: The creation of emission-free zones and the adoption of clean energy can significantly reduce pollutants. In addition, the promotion of regulations that limit the use of highly polluting cars is key.
- Business: Many of the main pollutants come from industries. Implementing filtering systems and reducing emissions are necessary to combat smog.
- Citizens: Changing our daily habits, such as using public transport or opting for electric vehicles, helps reduce our carbon footprint.
Furthermore, nature plays a key role in the fight against smog. Rain and wind, when frequent, help to clean the atmosphere naturally, which explains why smog is more common in areas with dry climates.
Of course, all these efforts must be combined to achieve a real impact in reducing smog in the most affected cities and, consequently, improving air quality and the health of their inhabitants.