Air Pollutants: The Worst Offenders Revealed

Air pollution is one of the most pressing issues facing humanity today, with millions of deaths attributed to it every year. The World Health Organization (WHO) states that 99% of humans currently breathe air that exceeds the safe limits for pollutants, with people in low- and middle-income countries suffering the most. The top polluting sectors are those that emit large amounts of greenhouse gases and contribute significantly to the global carbon footprint. These include the fossil fuels industry, fashion, food retail, transport, and construction. Other sources of air pollution include car and truck exhaust, factories, dust, pollen, mold spores, volcanoes, and wildfires. Climate change also increases the production of certain air pollutants, such as mold and pollen, and sets the stage for dangerous wildfires, which can release particulate matter into the atmosphere.

Fossil fuels

The burning of fossil fuels is a major source of airborne particulate matter (PM) and ground-level ozone, which have been linked to mortality and disease. PM2.5, or fine particulate matter, is any airborne particle that is up to 2.5 microns in diameter, about one-thirtieth the width of a human hair. These particles are problematic as they linger in the air, are easily inhaled, and can penetrate deep into the lungs, entering the bloodstream and causing damage to multiple organs. The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD 2015) identified ambient air pollution as a leading cause of the global disease burden, especially in low- and middle-income countries.

Nitrogen oxides (NOx) are formed when fossil fuels are burned, causing nitrogen in the air to react with oxygen. NOx can cause acid rain, threatening wildlife and ecosystems, and having a large impact on human health. Sulphur dioxide (SO2) is another pollutant produced by burning fossil fuels, particularly coal, and can be removed from smokestacks in coal plants using filtering technologies. Fossil fuel combustion also produces soot, or black carbon (BC), which is formed when materials such as fossil fuels like coal are burned.

A global phase-out of fossil fuels would have significant health benefits, as switching to clean, renewable energy sources would reduce air pollution and help combat global heating. Countries like the United Kingdom have successfully reduced emissions by moving away from fossil fuels, particularly coal, in electricity production, and setting pollution control standards for automakers.

Transport

Passenger vehicles are regulated by the US Environmental Protection Agency (EPA) under light-duty vehicle programs. The EPA has set stringent emissions standards for passenger vehicles, as well as limits on the amount of sulfur in gasoline. Limiting sulfur in gasoline allows emission reduction technologies like catalysts to be significantly more effective in reducing nitrogen oxides and other pollutants. Nitrogen oxides (NOx) are a group of gases, mostly made up of nitric oxide (NO) and nitrogen dioxide (NO2). They are formed when fossil fuels are burned, causing nitrogen in the air to react with oxygen. NOx can cause acid rain, threatening wildlife and ecosystems, and it has a particularly large impact on human health. The EPA has also implemented standards to reduce emissions from heavy-duty diesel vehicles and engines. The Diesel Emissions Reduction Act program offers funding in the form of grants and rebates, as well as other support for projects that protect human health and improve air quality by reducing harmful emissions from diesel engines. Between 2009 and 2018, over 73,000 engines were retrofitted or replaced through this program.

Freight transportation is a large contributor to air pollution and climate change. The EPA's SmartWay program helps the freight transportation industry improve supply chain efficiency to reduce air pollution from their operations. The program's three core elements include transport partnerships between shippers and carriers and the EPA, brand awareness of fuel-saving technologies, and global collaboration. The EPA's Ports Initiative is also working to develop and implement environmentally sustainable port strategies through partnerships with ports.

In Europe, the introduction of targeted policies and measures in recent decades has led to a decrease in the emission of most air pollutants from transport in the EU-27. Reductions in the road transport sector account for the greatest share of this progress. However, emissions from shipping and aviation have increased for some pollutants. The COVID-19 pandemic led to a temporary reduction in emissions due to decreased transport volumes, but an upturn in pollution from transportation was already visible in 2021 and 2022 as transport volumes rebounded. Between 1990 and 2022, transport emissions of ammonia (NH3) increased by 121%, while nitrous oxide (N2O) increased by 35%. While the transport sector's contributions of NH3 emissions are limited compared to other sectors such as agriculture, their impact on air quality, especially within cities, is reported to be very high.

To reduce emissions from aviation, airplanes can use clean fuels to reduce the amount of pollutants released into the air. Jet fuels with high aromatics and naphthalene concentrations increase soot formation, which in turn leads to persistent contrail cirrus. One way to reduce aromatics and naphthalene in jet fuel is to perform hydrotreating on fossil jet fuels. Reducing the aromatics content of fossil jet fuel down to 8-10% can be achieved without significant costs and could lower non-CO2 effects significantly. Flying less could also help reduce aviation emissions, as could taking a more sustainable mode of transport, such as trains.

Fashion

The fashion industry's environmental impact has been exacerbated by the rise of fast fashion and its associated excessive production, complicated supply chains, and rapid consumption. The industry's manufacturing and marketing techniques have led to increased air and water pollution. For example, the use of steam power in the 19th century resulted in the "Black Ditch" in Manchester, which was described in newspaper reports as a public nuisance due to the contamination from "waste dye stuff and filth."

Today, the fashion industry continues to rely on toxic chemicals and non-renewable resources, such as water and fossil fuels. Textile dyeing is the world's second-largest polluter of water, as the leftover water from the dyeing process is often dumped into natural water sources. Additionally, the industry uses synthetic fibres like polyester, nylon, and acrylic, which take hundreds of years to biodegrade and contribute to microfiber pollution in the soil, air, lakes, and oceans.

The fashion industry also contributes to air pollution through the incineration of unsold clothing and the release of chemicals during the decomposition of clothing in landfills. Improper disposal methods allow these chemicals to leach into the air and groundwater, affecting both surface and drinking water. Furthermore, the fashion industry's global supply chains contribute to pollution through the use of pesticides and manufacturing chemicals, which enter human food chains.

To address these issues, consumers are encouraged to move away from fast fashion, buy fewer but higher-quality garments, and support sustainable brands that are transparent about their environmental impact and actively work to reduce it.

Food waste

When food is wasted, the resources used to produce it, such as land, water, energy, and natural resources, are also wasted. Food waste accounts for one-third of all human-caused greenhouse gas emissions, generating 8% of global emissions annually. This is due to the production of methane, a greenhouse gas more potent than carbon dioxide, when food rots in landfills. The environmental impact of food waste is further exacerbated when considering the energy and resources expended in processing, transporting, storing, and cooking food that ultimately goes to waste.

Food loss, which occurs during the early stages of the production process, can be attributed to factors such as insufficient skills, natural disasters, inadequate infrastructure, and poor practices. Food waste, on the other hand, refers to the intentional discarding of edible food by consumers, often due to spoilage, expiration, or simply being thrown away. Overproduction by restaurants, grocery stores, and similar establishments also contributes to food waste, as they may order more perishable food than they can sell.

To address food waste, individuals can take several actions, such as planning meals, creating shopping lists, using leftovers creatively, and freezing food to extend its shelf life. Educating consumers about food waste prevention has the potential to significantly reduce greenhouse gas emissions. Additionally, legislative actions, such as France's law prohibiting supermarkets from throwing away food, can help redirect surplus food to those in need.

Overall, reducing food waste is crucial in mitigating air pollution and its associated environmental and social impacts. By preventing food waste, we can conserve resources, reduce emissions, and contribute to a more sustainable food system.

Nitrogen oxides

NOx emissions have a significant impact on both human health and the environment. When inhaled, NO2 can irritate the airways and aggravate respiratory diseases, especially asthma. Prolonged exposure to elevated levels of NO2 may contribute to the development of asthma and increase susceptibility to respiratory infections. Additionally, NOx can react with ammonia, volatile organic compounds (VOCs), and other compounds to form PM2.5 pollution, which can easily penetrate sensitive and deep parts of the lung, causing respiratory diseases such as emphysema and bronchitis.

NOx also contributes to nutrient pollution in coastal waters and plays a role in the formation of ground-level ozone, often referred to as the "bad" ozone. This type of ozone acts as a dense barrier, preventing pollution from escaping the higher atmosphere. It is formed when NOx combines with VOCs and reacts with sunlight and heat. Ground-level ozone is commonly found near urban centres due to its sources, which include car emissions, power plants, refineries, and chemical plants.

To address the harmful effects of NOx, regulatory bodies such as the US Environmental Protection Agency (EPA) have implemented standards and regulations to reduce NO2 and NOx emissions. These efforts include identifying areas with high NO2 levels and working with state, local, and tribal governments to develop plans to improve air quality. Additionally, the use of catalytic converters in vehicles has proven effective in reducing NOx emissions by splitting NOx compounds into nitrogen and oxygen before they are released into the atmosphere.

While progress has been made in reducing NOx emissions, it remains a significant contributor to air pollution, particularly in areas with high fuel consumption and industrial activity. By continuing to implement regulations, adopting cleaner technologies, and transitioning to renewable energy sources, further reductions in NOx emissions can be achieved, leading to improved air quality and public health outcomes.

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