An Aerial View of the Morning Smog in Delhi,Capital of India

Ecology: An Overview of the Harmful Effects of Air Pollution Relative to Air Quality Index

Do you wake up in the morning with watery eyes and an inability to breathe properly? The culprit behind the problem is the spike in air pollution which causes a sky-high air quality index. Specifically, air pollution refers to the release of pollutants into the air—pollutants that are detrimental to human health and the planet as a whole. According to the World Health Organization (WHO), each year air pollution is responsible for deaths. Especially because of the staggering statistic of nearly seven million deaths around the globe. While nine out of ten human beings currently breathe air that exceeds the WHO’s guideline limits for pollutants. Moreover, those living in low- and middle-income countries suffer the most. In the United States, the Clean Air Act, established in 1970, authorizes the U.S. Environmental Protection Agency (EPA) to safeguard public health by regulating the emissions of these harmful air pollutants.

While in India, the spike occurs every year when the cold months of the winter season approaches. But the atmosphere worsens, driving up the air pollution levels in Northern India. Mainly into the hazardous category of the Air Quality Index. One such startling factor is that the air pollution levels in India are among the highest in the world. Furthermore, they pose a significant threat to the country’s health and economy. Moreover, almost all of India’s 1.4 billion people are exposed to unhealthy levels of ambient PM 2.5( Particulate Matter) – the most harmful pollutant – emanating from multiple sources. But you must be wondering what exactly does the term particulate matter mean and how pollution in one area can spread to another?

Types of Air Pollution

Particulate Matter
Particulate Matter








Ground Level Ozone
Ground Level Ozone

Photo Credits: US Environmental Protection Agency

The two types are fine particulate matter (PM2.5) and ground-level ozone. They are invisible to the naked eye and present both indoors and out. PM2.5 penetrates the lungs and allows toxic compounds into the bloodstream. While ground-level ozone is both greenhouse gas and an air pollutant, it is damaging to human and ecosystem health. Specifically, exposure to ground-level ozone causes 472,000 premature deaths every year.

What is Particulate Matter?

Essentially, they are small particulates with a diameter of fewer than 2.5 microns, which is about one-thirtieth the width of a human hair. Significantly, any type of exposure to PM 2.5 can cause such deadly illnesses as lung cancer, stroke, and heart disease. Specifically, ambient and indoor air pollution is the cause of 1.7 million premature deaths in India in 2019. The health impacts of pollution also represent a heavy cost to the economy. Whereas the lost labour income due to fatal illness from PM 2.5 pollution in 2017 was in the range of $30-78 billion. Consequently, this equals the magnitude of about 0.3-0.9 per cent of the country’s GDP( Gross Domestic Product: used as a tool to measure the growth of a country).

Sources of 2.5 Particulate Matter

Specifically, PM 2.5 comes from a variety of sources. Some of the most common sources include emissions from burning fossil fuels. Specifically, from coal or oil and biomass such as wood, charcoal, or crop residues. The PM 2.5 can also come from windblown dust. Additionally, including natural dust as well as dust from construction sites, roads, and industrial plants.

Whereas over half of PM 2.5 emissions in India are formed in a “secondary” way in the upper atmosphere. Especially when different types of gaseous pollutants from one area, such as ammonia (NH3), mix with other gaseous pollutants like sulfur dioxide (SO2), and nitrogen oxides (NOx) from another place. Specifically, agriculture, industry, power plants, households, and transport all contribute significantly to the formation of secondary PM 2.5. Consequently, this secondary form spreads farther and wider than primary PM2.5 and travels across states, cities, and crosses jurisdictional borders.

Sources of Air Pollution

Sources of Air Pollution
Sources of Air Pollution

Photo Credit: Pan American Health Association

The various sources of air pollution are classified into seven major sectors, which include transportation, industries, agriculture, power, waste treatment, biomass burning, residential, construction, and demolition waste.

Air pollutants can be released directly into the atmosphere (primary emissions) or can form as a result of chemical interaction involving precursor substances. The air pollutant emissions cause air pollution. However, reductions in emissions do not always automatically result in similar cuts in concentrations. There are complex links between air pollutant emissions and air quality. These include emission heights, chemical transformations, reactions to sunlight, additional natural and hemispheric contributions and the impact of weather and topography.

Transportation as a Source of Air Pollution

The transportation sector is the main contributor to air pollutants in almost every city. But this phenomenon is worse in urban cities. This could be due to the increased number of vehicles when compared to the existing infrastructural facilities. For e.g., roads, fuel stations, and the number of passenger terminals provided for public transport.

After World War II, economic growth, population growth, rapid suburbanization. And the closing of some public transit systems has led to more reliance on personal vehicles for transportation. The number of cars and trucks in the United States increased dramatically, as did the number of highways. One result of the rapid increase in motor vehicles was air pollution, especially in cities, which has a serious impact on public health and the environment.

Transportation sources account for approximately a third of PM pollution in India. Additionally, a somewhat higher proportion of nitrogen oxides, another set of compounds harmful to human health. Because its vehicle fleet is small relative to its large population, India has very low per capita transportation emissions. But that fleet is growing rapidly: total vehicle sales (including motorcycles) saw a jump from about 10 million in 2007 to over 21 million in 2016, and the expectation with regards to the total number of vehicles on the road is to be nearly double to about 200 million by 2030. In an urban environment, road traffic emissions are one of the prime contributors to air pollution. In the Indian context, some of the essential factors of high traffic emissions. Essentially, including the extreme lack of exhaust measures, the highly heterogeneous nature of vehicles, and the poor quality of fuel.

Urbanisation and Industrialisation

Rising urbanisation, booming industrialisation, and associated anthropogenic activities are the prime reasons that lead to air pollutant emissions and poor air quality. It is an expectation that by 2030, around 50% of the global population will be residing in urban areas. More than 80% of the population in urban areas is exposed to emissions that exceed the standards set by World Health Organization (WHO 2016).

Air pollution is one of the key global health and environmental concerns and is among the top five global risk factors for mortality by the Health Effects Institute (HEI 2019). According to HEI’s report, particulate matter (PM) pollution falls third on the list as one of the most important causes of death in 2017.  Air pollution is to blame for the cause of over 1.1 million premature deaths in 2017 in India (HEI 2019). Moreover, of which 56% was due to exposure to outdoor PM2.5 concentration. And 44% of the pie goes to household air pollution. As per WHO (2016), one death out of nine in 2012 is the culprit behind the accelerating air pollution. Mainly, out of which three million deaths are solely due to outdoor air pollution.

Population Growth

The rising trends in population growth and the consequent effects on air quality are evident in the Indian scenario. For example, the megacities of Delhi, Mumbai, and Kolkata combined to hold a population exceeding 46 million (Gurjar, Ravindra, and Nagpure 2016). Additionally, over the years, there has been a massive-scale expansion in industries, population density, anthropogenic activities. And the increased use of automobiles. This has degraded the air quality in India (Gurjar and Lelieveld, 2005). In the last few decades, greenhouse gas (GHG) emissions and other emissions. This results in a drastic increase in anthropogenic activities (Gurjar and Nagpure 2016).

As per WHO (2016) estimates, 10 out of the 20 most populated cities in the world are in India. And based on the concentrations of PM2.5 emissions, India was ranked the fifth most polluted country by WHO (2019), in which 21 concentrations of the top 30 polluted cities were in India. The Indian cities, on average, exceeded the WHO threshold by an alarming 500%. The consistent population growth has led to an excessive strain on energy consumption. This has thereby led to affecting the environment and the air quality of the megacities.

Industrial Processes

Whereas over the last few decades, India has witnessed large-scale industrialisation. Specifically, this has led to the degradation of the air quality in most urban cities. In particular, the Central Pollution Control Board (CPCB) has categorised the polluting industries into 17 types. In particular, these fall under the small and medium scale. Meanwhile, out of these categories, seven have been marked as ‘critical’ industries. Essentially, these include iron and steel, sugar, paper, cement, fertiliser, copper, and aluminium. Significantly, the major pollutants comprise SPM, SOX, NOX, and CO2 emissions.

Similarly, the small-scale industries, which are not under regulation like the major industries, use several energy sources apart from the primary source of state-provided electricity. Moreover, some of these fuels include the use of biomass, plastic, and crude oil. Most importantly, these energy sources aren’t being taken into consideration in the current emission inventory studies. Importantly, in Delhi, after the intervention of the judiciary in 2000, many industries underwent relocation from urban areas to adjacent rural areas. In Delhi, a major fraction of the pollution load comes from the brick manufacturing industries, which are situated on the outskirts of the city. Whereas Rajkot (42%) and Pune (30%) are the two cities where industries play a prominent role in contributing to the highest amount of PM2.5.


Agricultural activities produce emissions that have the potential to pollute the environment. Consequently, namely, Ammonia (NH3) and nitrous oxide (N2O) are the key pollutants along with agricultural activities. Furthermore, the other agricultural emissions include methane emissions from enteric fermentation processes, nitrogen excretions from animal manure, such as CH4, N2O, and NH3, and methane emissions from wetlands.

Moreover, nitrogen emissions from agricultural soils (N2O, NOX, and NH3) are due to the addition of fertilisers and other residues to the soil (Gurjar, Aardenne, Lelieveld, et al. 2004). Specifically, agricultural processes, such as ‘slash and burn’ are prime reasons for photochemical smog resulting from the smoke generated during the process. Meanwhile, crop residue burning is another process that results in toxic pollutant emissions.

Significantly, this is how neighbouring cities of Delhi contribute to the agricultural pollution load. And this is an example of how external sources contribute to the menace of air pollution in the city.

Indoor Pollution

Specifically, people tend to think of air pollution as something that happens ‘outside’. Whereas even in the most industrialized cities, the air inside many buildings and homes is often more polluted than outdoor air. Moreover, to make matters worse, research shows that people now spend approximately 90% of their time indoors.

Specifically, inside air can be contaminated by infiltration from outside sources. For example, fine particulate matter from smoke or vehicle exhaust is so tiny it easily infiltrates homes through openings and even directly through the walls. Subsequently, serious indoor pollution can occur in airtight homes when ventilation intake vents are near smoke or exhaust sources.

Harmful Effects of Air Pollution on Air Quality

A table detailing the Air Quality Index Ranges and their impact on health of people
A table detailing the Air Quality Index Ranges and their impact on the health of people

Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 or below represents good air quality, while an AQI value over 300 represents hazardous air quality.

In particular, for each pollutant, an AQI value of 100 generally corresponds to an ambient air concentration that equals the level of the short-term national ambient air quality standard for the protection of public health. While AQI values at or below 100 are generally thought of as satisfactory. Whereas the AQI values are above 100, air quality is unhealthy: at first for certain sensitive groups of people, then for everyone, as AQI values get higher.

The AQI is divided into six categories. Each category corresponds to a different level of health concern. Specifically, each category also has a specific colour. Essentially, the colour makes it easy for people to quickly determine whether air quality is reaching unhealthy levels in their communities.

Air Quality Index (AQI) Calculation

The Air Quality Index is based on the measurement of particulate matter (PM2.5 and PM10), Ozone (O3), Nitrogen Dioxide (NO2), Sulfur Dioxide (SO2) and Carbon Monoxide (CO) emissions. Moreover, most of the stations on the map are monitoring both PM2.5 and PM10 data, but there are a few exceptions where only PM10 is available.

Top 10 Air Quality Indexes all around the World

Major city US AQI
1 Delhi, India Delhi, India 488
2 Lahore, Pakistan Lahore, Pakistan 211
3 Mumbai, India Mumbai, India 169
4 Kolkata, India Kolkata, India 155
5 Wroclaw, Poland Wroclaw, Poland 154
6 Dhaka, Bangladesh Dhaka, Bangladesh 154



Krakow, Poland Krakow, Poland 152
8 Belgrade, Serbia Belgrade, Serbia 151
9 Kyiv, Ukraine Kyiv, Ukraine 133
10 Warsaw, Poland Warsaw, Poland 131


Measures Undertaken to Reduce Air Pollution


Photo Credit: Climate and Clean Air Coalition

The continuous degradation of ambient air quality in the urban centres of India demands effective measures to curb air pollution. Moreover, through various policy measures being introduced by the Government of India (GoI) to reduce vehicular and industrial emissions, the extent to which these measures are implemented is questionable.

The lack of infrastructural facilities, the inadequacy of financial resources to implement them. These are namely, advanced infrastructural innovations, difficulty in the relocation of industries. Especially in the urban centres, even after mandatory court decisions, and above all, the behavioural patterns among people in accepting green solutions are some of the crucial impediments on the road to environmental protection that the country of India seems to be struggling to overcome today.

The air pollution challenge in India is inherently multi-sectoral and multi-jurisdictional. To understand this statement, firstly, the common geographic area where pollutants mix and create similar air quality for everyone is called an airshed. However, cities need to look beyond their immediate jurisdiction for effective air pollution control strategies. And apply a new set of tools for aisle-based management. Also, standardizing tools across India is important, so the link between control strategies and relevant data sets.

In more than 155 countries, a healthy environment is recognized as a constitutional right. Obligations related to clean air are implicit in the Universal Declaration of Human Rights and the International Covenant on Economic, Social and Cultural Rights.

Whereas to tackle global air pollution, the 2030 Agenda pursues Sustainable Development Goals. Mainly with a view to “leave no one behind” and the Paris Agreement requires parties to report their progress in limiting global temperature increases.


Ways to Keep the Air Clean
Ways to Keep the Air Clean

Photo Credit: GreenDallas

As air pollution is a matter of concern, another significant impact of air pollution is climate change. Air pollution is inextricably linked to climate change. Although they remain in the atmosphere for a much shorter period of time than CO2, short-lived climate pollutants like methane, black carbon and ground-level ozone have an outsized impact on global warming. Specifically, reducing them can cut the current rate of warming in half. And because ozone reduces the growth of plants and forests. It also results in a reduction in the amount of carbon- denying nature its most basic defence.

While the problem of air pollution may seem to be a difficult one to tackle. Essentially, you, as an individual, can be more responsible and take care of the very air that breathes life into your body. And here are some ways to do so: conserve energy, look for the ENERGY STAR label on home or office equipment. Most importantly, make use of carpool, use public transportation, bike, or walk. Follow gasoline refuelling instructions for efficient vapour recovery, be careful not to spill fuel and always tighten your gas cap securely.

Significantly, you can consider purchasing portable gasoline containers labelled “spill-proof,” where available, and keep the car, boat, and other engines properly tuned. Specifically, be sure your tires are properly inflated. Moreover, you can use environmentally safe paints and cleaning products whenever possible. Make use of mulch or compost leaves and yard waste and consider using gas logs instead of wood for fireplaces.

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