**1. Introduction**

Air pollution has become a major health hazard to the millions of people around the globe. It has been linked to asthma, heart disease, and other serious health problems. Air pollution triggers asthma, which is a long-term disease of the lungs that affects the airways and makes it hard to breathe. Tiny particles in the air get deep into the lungs and cause inflammation, which can lead to an asthma attack. Cardiovascular diseases such as heart attacks and strokes have also been linked to air pollution. Nitrogen oxides and sulfur dioxide are also causes of oxidative stress, which can lead to heart problems. Various studies have shown that the exposure to air pollution increases the probability of early decay and death among the living organisms. This is especially true for the elderly and people who already have health problems. Adult's lung function is adversely correlated with PM10, nitrogen dioxide, and sulfur dioxide, all of which have been linked to bronchitis symptoms in studies encompassing eight different communities. Research into the effects of air pollution has also revealed a decline in human lifespan [1].

**Figure 1.** *Effects of air pollution on various sectors.*

Air pollution not only harm people's health, but also affects the environment in various ways (**Figure 1**). Here are some primary ways that pollution in the air can affect nature. Air pollutants in form of acid rain have detrimental effects on crops and forests growth [2]. Furthermore, the damage of leaves hinders crop yields [3]. This issue contributes to food insecurity and disturbs plant ecosystems. For instance, acid rain makes lakes and streams more acidic, and it is hard for certain species to survive. Similarly, carbon dioxide, methane, and other greenhouse gases are examples of air pollutants that contribute significantly to global warming and climate change [4]. This results in glaciers melting, rising sea levels, and stronger weather events. The poor air quality causes smog and haze, which makes it difficult for the people to enjoy the outdoor activities [5]. Moreover, air pollution can also have a significant negative effect on various businesses, tourism industry, and ultimately the economy of the region [6].

In order to mitigate air pollution, it is very important to understand the origin, sources, and classification of air pollutants. Moreover, the life cycle of the air pollutant can provide a better insight to manage the potential sources causing air pollution in a system. The major contributor in deterioration of air quality is the energy sector; hence, it is also important to study air pollution in connection with the energy generation systems for sustainability of environment as well as communities. Keeping in view such factors, this chapter summarizes a thorough overview of air pollution, including its causes, types, and classification as well as the use of clean energy resources for minimizing the discharge of pollutants and contaminants in the air. Different factors associated with air pollution such as its effects on health, environment, climate, and the most recent trends in air pollution are also discussed.

#### **1.1 Overview of air pollution**

Pollution is addition of any foreign matter, which changes the purity of any system. Hence, air pollution can be defined as "it is the addition of any foreign and undesirable matter generated from physical, chemical, or biological sources which alters the natural quality of ambient air." Having complex mechanisms composed of both primary and secondary pollutants formulations, it is very difficult to exactly determine the air pollution. It might be argued that the use of fossil fuels and primary/finite energy resources is one of the main causes of air pollution. All anthropogenic effluents and emissions into the air are considered as air pollution due to their impact on atmospheric chemistry. Using this definition, the rise in atmospheric levels of greenhouse gases CO2, CH4, and N2O can be considered as air pollution, even *Air Pollution and Clean Energy: Latest Trends and Future Perspectives DOI: http://dx.doi.org/10.5772/intechopen.112226*

though these levels are not yet known to be harmful to humans or ecosystems. Air pollution can narrowly be defined as harmful chemicals released into the atmosphere by humans. The term "harmful" can refer to a variety of negative outcomes, that is, damage to manmade or naturally occurring inanimate structures, and a decrease in visibility. A chemical may have no immediate negative effects before being released into the environment [7, 8]. Hence, it is important to classify the discrete sources of air pollution for its proper mitigation and minimization.

#### **1.2 Sources of air pollution**

Pollutants in the air are divided into groups based on their origin. Based on such classification system, it becomes easy for the environmentalists to make policy decisions for specifying the release and control of air pollutant in the air.

The sources of air pollution are classified into following three major groups (**Table 1**):

#### *1.2.1 Natural sources of air pollution*

This category includes the addition of undesirable elements in the ambient air particularly, due to natural incidents occurring in the earth's atmosphere. Such elements that pollute the air include sand or dust particles, forest fires, pollen, volcanic eruptions, SMOG, release of gases from organic matters, etc. These pollutants are liberated as by-products from the cycles or incidents occurring naturally.

Sandstorms are one of the most common sources, which deteriorate the air quality. The immediate effect of sandstorm is to worsen the clarity of air and reducing the visibility and ultimately causing road accidents and difficulties in transportation. Dust particles are more likely to absorb toxic gases, which can cause severe reactions to form secondary pollutants. This also becomes a source of toxic organic compounds


**Table 1.** *Sources of air pollution [9–19].*

that make aerosols in the urban environment more toxic and biologically reactive. Dust particles act as media to transport bacteria. Studies have shown that microberich dust particles can make allergic inflammation worst [20].

Another source for air pollution is forest fires, which occur as a result of natural accidents like lightning or temperature increase in the certain region that has sufficient biomass to burn up. Open fire at a massive scale in the forest releases a lot of smoke and small particles into the air. Pollutants such as oxides of carbon, that is, carbon dioxide (CO2) and carbon monoxide (CO), oxides of nitrogen and sulfur in the form of NOx and SOx, volatile organic compounds (VOCs), as well as fine ash and particulate matter are produced from forest fire. These pollutants can lead to health problems like asthma and lung diseases [21].

Volcanic eruptions are one of the most natural and powerful sources of air pollution. Volcano eruption produces aerosol clouds that can travel thousands of miles, blocking the sun and causing health problems, crop damage, and other types of environmental damage. Volcanic eruptions can have far-reaching and terrible effects on the environment in the long run [22].

Similarly, breaking down of organic matter naturally is a major source of air pollution. As organic matter is destructed by the microorganisms in an uncontrolled manner, it gives off gases called volatile organic compounds (VOCs) and other air pollutants. These pollutants can be harmful and can contribute in the formation of smog and ozone, both of which are hazardous to health. Furthermore, such process of organic matter decomposition can also release methane (a strong greenhouse gas), which significantly contributes to climate change and global warming around the world [23].

#### *1.2.2 Industrial or manmade sources of air pollution*

Industrial sources of air pollution include all kinds of particulates and gases, which are generated by industrial activities. Stack emissions, that is, release of carbon monoxide, oxides of sulfur dioxide, and oxides of nitrogen due to the burning of fossil fuels, are the most significant elements under this category. Uncontrolled burning of fossil fuels in the energy generation systems at the industrial power units results in complete burning, which liberates toxic pollutants. These pollutants can cause a wide range of health problems, such as cancer and lung diseases. Moreover, such elements are also responsible for the acid rain that damages the local environment and the ecosystem [9].

Metal melting, preparing chemicals, treatment of fluids, and production of cement are all examples of industrial processes that release pollutants into the air [10]. Similarly, farming activities, that is, the use of chemicals in the form of pesticides, fertilizers as well as transportation activities are also the sources of air pollution. Loose and uncontrolled burning of agricultural residues and leftovers has also a major share in air pollution by adding combustion gases directly to the environment leading to the formation of smog and other secondary pollutants [11, 12].

The extraction of minerals and oil and gas refineries are the sources to add sulfur dioxide, VOCs, oxides of nitrogen, and heavy metals into the air [13, 14].

#### *1.2.3 Municipal and domestic sources of air pollution*

The municipal and domestic sources of air pollution include methane and other toxic gases produced in the landfills, which contribute to deterioration of air quality in the habitat [15]. Uncontrolled sewage gas is released in the municipal sewerage

*Air Pollution and Clean Energy: Latest Trends and Future Perspectives DOI: http://dx.doi.org/10.5772/intechopen.112226*

**Figure 2.** *Sources of air pollution.*

systems, which may cause addition of potential pollutants and toxic fumes in the air [16]. Household activities such as cooking are also a source of pollutants such as particulate matter and volatile organic compounds as shown in **Figure 2** [17–19].

The above sources generically include the major contributors in the deterioration of air quality. However, air pollution dates back to the industrial revolution in the nineteenth century. At that time, people burned coal for energy and transportation, which made the air in cities much polluted. The Great Smog of 1952 in London, England, was one of the first documented cases of air pollution. Thousands of people were affected, which led to the formulation of the Clean Air Act in 1956 [24]. In the 1960s and 1970s, after being more aware about the possible effects of poor air quality and contaminants on health and ecosystem, further strict rules were also structured such as the Clean Air Act Amendment, which was passed in 1963. The formulation of Environmental Protection Agency (EPA) in the United States in 1970 also played an important role to control air pollution (Environmental Protection Agency, 2023). In the last few decades, air pollution has become a global issue. The rapid growth of industry and transportation has affected the air quality badly.
