Air Pollution


What is air pollution?

Air pollution is the presence of unwanted substances or pollutants which have an adverse effect on humans, animals and plants, and for sure on the air quality. The frequently present categories contributing to the air pollution are sulphur oxides, nitrogen oxides, Volatile Organic Compounds (VOC) and small dust particles.

What causes air pollution?

The main causes of air pollution are the traffic, industries and agriculture. During all these processes, air pollutants are emitted. Large concentrations of substances like Volatile Organic Compounds negatively affects public health and ecosystem.

Traffic is held responsible for air pollution most of the times. Emissions caused by traffic are mainly includes carbon dioxide, carbon monoxide, nitrogen oxides, VOC and small dust particles.

Industrial processes are responsible for the emission of chemical wastes in large quantities. Industrial processes leads to the emission of carbon dioxide, carbon monoxide, nitrogen oxides, sulphur dioxide, VOC and methane.

Nitrous oxide is mainly caused from agriculture processes as denitrification process includes emission of mitrous oxide. Also, the application of fertilizers causes emission of ammonia, nitrogen oxide and methane. The extensive use of pesticides also causes the emission of many toxic chemicals.

Lastly, the indoor air pollution caused by the people or consumers. This leads to dual pollution as the products have caused air pollution in its manufacturing cycle, and later they cause air pollution in its distribution and application.

What are the main environmental effects of air pollution?

The main environmental effects of air pollution are briefed below:

Acid Deposition

Acid deposition can be primarily characterized as acid rain, snow and fog or gas and dust is one of the main effects of air pollution. During fuel combustion, acid deposition is mainly formed as emission of nitrogen oxide and sulphur dioxide becomes sulphuric acid and nitric acid when are in contact with water.


Eutrophication is caused in water by an increase in plant nutrients. The higher availability of nutrients in water plants like duckweed and algae to grow extensively. The extensive growth blocks the sunlight supplies to water. Also, the plants use all available oxygen, which cannot be renewed as heterotrophic plants need light to perform photosynthesis.


A combination of words smoke and fog. Smog is of two types summer smog and winter smog. Summer smog also called as photochemical smog is a brown oxidising fog mainly consisting ozone. The primary causes of photochemical smog are VOCs and nitrogen oxides which are emitted through vehicles and industries. Humans cannot adapt to smog as it causes eye and respiratory irritations. Ozone causes serious damage to plant as well.

Winter smog also referred as acid smog mainly consists of foggy elements. Winter smog is found in areas where vertical dispersion of air pollutants is nearly not possible. Temperatures decreases during the day. Winter smog is formed when temperature is low and the sulphur dioxide concentration increases.

How does air pollutants spread and how to handle this?

How far air pollutants are transported primarily depends on the size of compounds and the height at which the pollution was emitted into the air. Fumes emitted into air through high smoke mixes with air maintaining the local concentrations. However, wind transports compounds making the pollution disperse. Rain removes pollutants from the air causing precipitation and consequentially soil and water pollution.

We can predict the dispersion of air pollutants very easily with the computer models as air is not a very complex medium. A computer model calculates by different parameters such as wind direction, wind speed, humidity, cloudiness and temperature. These predictions are of great value when toxic clouds are taken into consideration as they are a danger to human health.

What causes indoor air pollution?

The primary cause of indoor air pollution are the gases or particles into the air because of inadequate ventilation. Inadequate ventilation increases the indoor pollutant levels by not bringing in enough outdoor air to dilute indoor emissions which leads to the failure of carrying indoor air pollutants out of the household. Dust, moisture, fungus, molds, pet dander, Volatile Organic Compounds (VOC), odour causing contaminants, bacteria in washrooms, high humidity and temperature also increases the levels of indoor air pollution.

What is PM2.5?

Particles less than 2.5 µm (micrometres) are called Particulate Matter 2.5 or PM2.5. They are 1/30th of the average width of a human hair which makes it almost negligible that cannot be seen with naked eyes. Particulate matter 2.5 can be seen only with an electron microscope. PM2.5 or fine particulate matter is 2.5 micrometers or less in diameter. These fine particles are produced from combustion, motor vehicles, power plants, residential wood burning, forest fires, industrial processes and agricultural burning.

What is PM10?

All scientists classify particulate matter by size. PM10 or coarse are particulate matter having the diameter between 2.5 micrometers and 10 micrometers. Its slightly bigger in size than PM2.5 but if we take human hair as reference, it is too small in size as human hair is between 50-70 micrometers thick. They can be seen with naked eyes. Smoke and dust are examples of PM10.