Anthropogenic Air Pollution: Human Activities, Toxic Air

Air pollution is a mix of hazardous substances from both human-made and natural sources. Human-made or anthropogenic sources of air pollution include vehicle emissions, fuel oils, natural gas, by-products of manufacturing and power generation, fumes from chemical production, and more. The problem of air pollution has existed since humans started burning materials for fuel, and it has now become an environmental and public health issue, causing millions of premature deaths every year.

Anthropogenic Sources of Air Pollution

Energy consumption and technical evolution

The combustion of fossil fuels, such as coal, oil and gas, is a major source of air pollution. The burning of these fuels releases a variety of pollutants, including carbon dioxide, carbon monoxide, nitrogen oxides, particulate matter, sulfur dioxide, and volatile organic compounds. In the US, stationary fuel combustion sources, such as utilities and industrial boilers, are responsible for a large proportion of sulfur dioxide pollution. Coal-fired power plants emit significant amounts of mercury into the atmosphere. The burning of fossil fuels in vehicles, planes, factories, and for heating homes, is a major contributor to carbon dioxide emissions, with transport, manufacturing, and construction identified as significant pollution sources.

The increased use of vehicles has led to nitrogen dioxide being the largest source of atmospheric pollution from vehicle exhaust. This, in turn, reacts with sunlight to create ozone, a harmful secondary pollutant. Friction from tires and brake wear also create particulate matter emissions. Urban roads are a sink for heavy metals, which accumulate from tire abrasion, fuel residues, and fluid leaks. The dust exposed to the air by moving vehicles mixes with the metal deposits on the road, and this process is more visible in dry weather.

The local climate is also affected by the heat generated by industry, households, agriculture, and transportation. This changes the local temperature of the lower atmosphere and is an example of physical pollution.

Urbanisation and population growth

One of the significant consequences of urbanisation and population growth is the increased consumption of resources and energy. This higher demand for energy, particularly in the form of fossil fuel combustion, results in the release of various pollutants into the atmosphere. For example, the burning of coal and oil in power plants, refineries, and factories emits carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulphur dioxide (SO2), and particulate matter (PM), among other pollutants. The increased energy consumption associated with urbanisation exacerbates the problem of air pollution.

Population growth in urban areas also leads to a rise in vehicle usage and traffic congestion. Petrol and diesel engines from cars, trucks, ships, and other vehicles emit pollutants such as carbon monoxide, nitrogen oxides, particulate matter, volatile organic compounds (VOCs), and sulphur dioxide. Friction from tires and brake wear further contribute to particulate matter emissions. The dense concentration of vehicles in urban areas, coupled with weak winds that hinder the dispersion of pollutants, results in poor air quality for city dwellers.

Additionally, urbanisation often involves land expansion and the reorganisation of industrial structures. This can lead to short-term environmental degradation, as observed by Yang et al. (2018). The transformation of land for urban use can result in the release of heavy metals and other pollutants into the air. For instance, the abrasion of tires, fuel residues, and fluid leakage from vehicles can contaminate road surfaces, and the subsequent movement of vehicles can stir up this contaminated dust, leading to air pollution.

Furthermore, population growth within cities can influence air pollution through economic growth and income levels. As urbanisation progresses, there is a positive correlation between population density and economic development, which can lead to increased industrialisation and energy consumption. This, in turn, contributes to higher emissions of pollutants. However, it is important to note that the relationship between urbanisation, population growth, and air pollution is complex and can vary depending on the size and development stage of the city.

Industrial and agricultural development

Industrial activities such as manufacturing, processing, and extraction of raw materials produce waste and emissions that contaminate the air, water, and soil. These activities release harmful pollutants, including PM2.5, silica dust, coal dust, methane, carbon monoxide, sulfur dioxide, nitrogen oxides, and volatile organic compounds (VOCs). In addition, heavy metals such as mercury and lead are released, causing toxic effects on human health and the environment. Refineries, steel mills, petrochemical plants, and power plants are significant contributors to industrial air pollution.

The energy consumption and technical evolution associated with industrial development have significantly impacted air quality. The burning of fossil fuels, such as coal, in power plants releases mercury and other hazardous pollutants into the atmosphere. The shift of industrial activities to regions with lax environmental regulations exacerbates the problem. Inadequate laws, poor enforcement, outdated technologies, and increased production contribute to higher emissions and industrial waste.

Agricultural activities also play a role in air pollution. According to the United Nations Environment Programme (UNEP), ground-level ozone pollution caused by fuel burning and chemical use will reduce staple crop yields by 26% by 2030. The use of certain equipment and practices on farms releases pollutants, and agricultural burning contributes to regional haze, reducing visibility. However, it is important to note that agriculture is not just a contributor to air pollution but also a victim of it. Air pollution can lead to lower crop yields, damaged crops, and other negative consequences for agriculture.

To address these issues, organizations like the Clean Air Council work with communities and governments to prevent hazardous industrial waste, oppose waste incineration, and advocate for comprehensive waste stream testing. The Environmental Protection Agency (EPA) in the United States studies emissions from agricultural operations and sets federal standards to limit them. State Implementation Plans (SIPs) are developed to identify sources of air pollution and implement measures to meet federal air quality standards. These collective efforts aim to reduce the impact of industrial and agricultural development on air pollution and protect public health and the environment.

Vehicle emissions and urban traffic

Urban areas, with their high population density, are particularly vulnerable to the effects of traffic-related air pollution. The congestion caused by a large number of vehicles on the road leads to increased emissions and degraded air quality. This is due to the increased number of speed-ups, slow-downs, stops, and starts, which result in higher emissions compared to uninterrupted "cruise" conditions. Additionally, congestion diminishes the dispersion of vehicle-related pollutants as turbulence depends on vehicle speed.

The health risks associated with traffic-related air pollution are significant. Epidemiological studies have shown excess morbidity and mortality for drivers, commuters, and individuals living near major roadways. The World Health Organization (WHO) has identified the risks of morbidity and mortality associated with exposure to vehicle emissions, particularly near large roadways. The impact of traffic congestion on air quality and health is particularly evident in highly developed urban clusters, such as the North China Plain and the Sichuan Basin.

To mitigate the effects of vehicle emissions and urban traffic on air pollution, various interventions have been proposed and studied. These include alternative fuel technology, vehicle emission regulation, vehicle ownership taxes, and studded tire regulations. Comprehensive temporal distribution approaches for vehicle emissions are also necessary to address the dynamic nature of traffic congestion and its impact on air quality.

While the development of a vehicle emission inventory has received attention and effort, limitations still exist. There is a need for a better understanding of real-time diurnal variations and increases in emission rates due to traffic congestion. This knowledge will inform the implementation of more effective vehicle emission control policies and improved road network planning to reduce congestion and enhance air quality, particularly in urban areas.

Fossil fuel combustion and power plants

Fossil fuels, such as coal, oil, and natural gas, have been the primary energy source for over a century, powering industries, businesses, and homes. However, burning these fuels releases harmful pollutants into the atmosphere, making fossil fuel combustion a significant contributor to air pollution. Power plants, in particular, are major sources of air pollution due to their extensive use of fossil fuels for electricity generation.

Fossil fuel combustion releases a range of toxic pollutants, including carbon dioxide (CO2), nitrogen oxides (NOx), sulfur dioxide (SO2), particulate matter (PM), volatile organic compounds (VOCs), and heavy metals. These emissions have severe environmental and health impacts, driving global warming and climate change. According to the US Energy Information Administration, burning fossil fuels accounts for about 80% of our energy needs, and in the United States, this combustion is responsible for about three-quarters of carbon emissions.

Coal-fired power plants are a significant concern within the fossil fuel combustion discussion. While coal only contains trace concentrations of mercury, the vast amounts burned annually result in substantial mercury emissions. Coal-fired power plants are responsible for approximately 35% of dangerous mercury emissions in the United States. Additionally, coal combustion releases large amounts of carbon dioxide, contributing to climate change and global warming.

The transportation sector is another major contributor to air pollution from fossil fuel combustion. Petrol and diesel engines in cars, ships, and planes emit pollutants such as carbon monoxide (CO), nitrogen oxides, particulate matter, sulfur dioxide, and volatile organic compounds. These emissions have detrimental effects on air quality and human health, particularly in densely populated urban areas.

To address the issue of air pollution from fossil fuel combustion and power plants, a transition to renewable energy sources is imperative. This includes adopting low-emission fuels, renewable combustion-free power sources like solar, wind, or hydropower, and improving energy efficiency. By implementing these measures, we can reduce air pollution levels, mitigate climate change, and improve the health and well-being of current and future generations.

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