What is Air Pollution

What is Air Pollution

“Source – SUSTENT Consulting Pvt. Ltd

Air pollution is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere. From smog hanging over cities to smoke inside the factory, air pollution poses a major threat to health and climate. The section below will discuss in detail about air pollution, its sources, types and impacts on human health.

5.1 Understanding Air Pollution (including Indoor Air Pollution)

Understanding the air around you is a challenge.

Answer the following questions to better understand the air around you:

  • Do you feel suffocated while doing your work?
  • Do you often sneeze while doing your work?
  • Do you experience redness/itching in your eyes while doing your work?

If the answer is yes, it implies that you are being affected by air pollution.

Ambient air pollution accounts for an estimated 4.2 million deaths per year due to stroke, heart disease, lung cancer, lung cancer, acute and chronic respiratory diseases1. Air quality is closely linked to the earth’s climate and ecosystems globally. Many of the drivers of air pollution (i.e., combustion of fossil fuels) are also sources of greenhouse gas emissions.

1WHO. 2021. Ambient (outdoor) air pollution.

Source of Air Pollution

The sources of air pollution include:

  • Mobile Sources– such as cars, buses, planes, trucks, and trains
  • Stationary Sources– such as power plants, oil refineries, industrial facilities, and factories
  • Area Sources– such as agricultural areas, cities, and wood burning fireplaces
  • Natural Sources– such as wind-blown dust, wildfires, and volcanoes

Figure 1: Sources of Air Pollution

Source: STENUM Asia

Likewise, the indoor sources of air pollution include tobacco smoke, combustion activities, building material, outdoor sources, fire retardant material etc.

Types of Air Pollutants:

Outdoor Air Pollutants

As per Clean air Act 1970, United States Environment Pollution Act (USEPA) has defined six criteria pollutants2 i.e.-

Table 1: Outdoor Air Pollutants and Emission Sources

Pollutant Type Major Sources of Emission
Carbon monoxide (CO) Vehicles, incomplete fuel combustion, unvented gas leak
ground level ozone (O3) Emitted due to photochemical reaction between Volatile Organic Carbons (VOCs) and Nitrogen Oxides (NOx). This happens when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources chemically react in the presence of sunlight.
sulphur dioxide (SO2) Fossil fuel combustion at power plants, volcanic eruption, burning of fuel with high S content
Lead (Pb) Ore and metals processing, lead smelters, lead acid battery manufactures, waste streams
Nitrogen dioxide (NO2) Vehicles and power plants
Particulate Matter (PM) Construction sites, unpaved roads, fields, smokestacks or fires, power plants and automobiles

 2USEPA. https://www.epa.gov/criteria-air-pollutants


Indoor Air Pollutants

Table 2: Outdoor Air Pollutants and Emission Sources3

Pollutant Type Source of Emission
Allergens House dust, domestic animals, insects
Asbestos Fire retardant materials, insulation
Carbon dioxide Metabolic activity, combustion activities, motor vehicles in garages
Carbon monoxide Fuel burning, boilers, stoves, gas or kerosene heaters, tobacco smoke
Organic substances Adhesives, solvents, building materials, volatilization, combustion,

paints, tobacco smoke

Polycyclic aromatic hydrocarbons (PAHs) Fuel combustion, tobacco smoke

 3Jones, A.P., 1999. Indoor air quality and health. Atmospheric environment, 33(28), Indoor air quality and health – ScienceDirect; www.sciencedirect.com


The major air pollutants of concern in food and beverage industry include Particulate matter and volatile organic compounds.

Figure 2: Key Pollutants in Indoor Air

Source: Tips to control indoor air quality 


5.2 Understanding the Effects of Air Pollution on Environment and Health

Figure 3: Health Effects of Air Pollution

Source: Dreamtime.com

The environmental impacts include:

  • Eutrophication: Eutrophication refer to natural ageing of lakes. The process is aggravated due to human practices which increases the rate at which nutrients enter the lake. Air emission like nitrogen oxides from power plants and vehicles accelerate the process of eutrophication by increasing the level of Nitrogen.
  • Acid Rain: Acid rain is precipitation containing nitric and sulfuric acids which are released into the atmosphere when fossil fuels are burned.
  • Haze: Haze-causing pollutants (mostly fine particles) are directly emitted to the atmosphere by sources such as power plants, industrial facilities, trucks and automobiles, and construction activities. It obscures the clarity, texture, and form of what we see when these particles encounter the sunlight.
  • Crop and Forest Damage: During increased concentration of ground level ozone, crops are majorly affected that reduces their yield and affects the growth and survival of plants as well.
  • Global Climate Change: Emissions of air pollutants into the atmosphere can result in changes to the climate. Ozone in the atmosphere can warms the climate, while different components of particulate matter (PM) can have either warming or cooling effects on the climate. For example, black carbon, a particulate pollutant from combustion, contributes to the warming of the Earth. Hence, air pollution is a contributing factor to global climate change.