Combustion's Pollution: Understanding The Harmful Emissions

The combustion of fossil fuels such as coal, oil, gasoline, and natural gas releases harmful emissions into the atmosphere, causing air pollution and contributing to global warming. This includes the emission of greenhouse gases, ultrafine particles, and toxic pollutants such as carbon monoxide, nitrogen dioxide, and polycyclic aromatic hydrocarbons (PAHs). The health impacts of combustion-related air pollution are significant, ranging from respiratory and cardiovascular issues to genetic damage and an increased risk of cancer and cardiopulmonary mortality. The combustion of solid fuels and kerosene used for cooking and heating in households is also a major source of indoor air pollution, particularly in low- and middle-income countries, leading to severe health issues and premature deaths. Additionally, the rising industrialization and locomotive activities in countries like China contribute significantly to the increasing global pollution levels, with a projected annual increase of 9% by 2030.

Fossil fuels and climate change

Fossil fuels are formed from the decomposition of carbon-based organisms that died millions of years ago. They create carbon-rich deposits that are extracted and burned for energy. They are non-renewable and currently supply around 80% of the world's energy. There are three types of fossil fuels: coal, oil, and natural gas.

The combustion of fossil fuels releases gases and particles that contribute to air pollution and climate change. The major indoor combustion pollutants include carbon monoxide (CO), nitrogen dioxide (NO2), fine and ultrafine particles, polycyclic aromatic hydrocarbons (PAHs), and formaldehyde. These pollutants have detrimental effects on human health, causing respiratory and cardiovascular diseases, lung damage, and increased vulnerability to toxic effects for young children, asthmatics, and people with heart or lung disease.

Outdoor combustion of fossil fuels, such as burning gasoline in vehicles, also contributes significantly to air pollution and climate change. In 2022, aviation and motor gasoline combustion accounted for about 22% of total U.S. energy-related CO2 emissions. The Clean Air Act in the U.S. aims to reduce air pollution by requiring engines and fuels to produce fewer emissions.

The Intergovernmental Panel on Climate Change (IPCC) has found that emissions from fossil fuels are the dominant cause of global warming. In 2018, 89% of global CO2 emissions came from fossil fuels and industry. Coal is the most polluting fossil fuel, responsible for over 0.3°C of the 1°C increase in global average temperatures. Oil is also a significant contributor, releasing approximately one-third of the world's total carbon emissions.

To limit global warming and mitigate climate change, the IPCC warns that fossil fuel emissions must be halved within 11 years. The Paris Agreement of 2015 committed world governments to reducing carbon emissions. However, a recent UN report indicates that global fossil fuel production is on track to exceed the limits required to keep warming below 1.5°C. Therefore, a rapid transition to renewable energy sources is necessary to address the urgent challenge of climate change.

Indoor air quality

One of the primary concerns regarding indoor air quality is the release of carbon monoxide (CO) during combustion. CO is a colorless and odorless gas that can reach dangerous levels indoors, especially in poorly ventilated spaces. It interferes with the body's ability to deliver oxygen, leading to symptoms that may be mistaken for the flu or food poisoning. High concentrations of CO can cause acute poisoning and are linked to non-accidental and cardiovascular diseases. California has recognized this issue by implementing the Carbon Monoxide Poisoning Prevention Act of 2010, mandating the installation of CO detectors in dwellings with fuel-type appliances.

In addition to CO, combustion appliances emit other harmful pollutants, including nitrogen dioxide, particles, and sulfur dioxide. These particles can be extremely fine, penetrating deep into the lungs and even entering the bloodstream. Incomplete combustion of solid fuels like coal can result in the release of pollutants such as formaldehyde, carbon dioxide, methane, and volatile organic compounds (VOCs). The adverse health effects of VOCs are well-documented and include eye and skin irritation, triggering asthma, damaging the cardiovascular system, and contributing to chronic diseases.

To maintain good indoor air quality, it is essential to use appliances properly and ensure they are well-maintained. For example, when using unvented kerosene or gas space heaters, it is crucial to follow the manufacturer's instructions and keep the room slightly ventilated. Regular maintenance of combustion appliances, such as furnaces, is also important, as they can corrode and leak combustion gases like carbon monoxide. Additionally, proper ventilation and the use of exhaust fans can help prevent the buildup of pollutants.

Furthermore, the World Health Organization (WHO) has issued guidelines for indoor air quality, providing recommendations on clean fuels and technologies. They discourage the use of kerosene and unprocessed coal, emphasizing the importance of addressing all household energy uses, especially cooking, space heating, and lighting, to protect health and the environment. WHO suggests cleaner alternatives, such as solar, electricity, biogas, liquefied petroleum gas (LPG), natural gas, alcohol fuels, and biomass stoves that meet emission targets.

Health risks

Combustion is a significant contributor to air pollution, which poses a range of health risks. The burning of fossil fuels, wood, natural gas, kerosene, charcoal, tobacco, and other solid fuels releases harmful gases and particles into the atmosphere, leading to indoor and outdoor air pollution.

One of the primary health risks associated with combustion is the release of carbon monoxide (CO). Carbon monoxide is a colorless and odorless gas that can be deadly, especially in enclosed spaces. It prevents the body from absorbing oxygen, leading to dizziness, headaches, fatigue, visual impairment, reduced work capacity, and poor learning ability. Incomplete combustion of fuels can also produce carbon monoxide, which is why proper ventilation and maintenance are crucial, especially in indoor spaces.

Nitrogen dioxide (NO2) is another significant pollutant produced by combustion. It is a reddish-brown gas with an irritating odor that affects the eyes, nose, and throat. High concentrations or prolonged exposure to nitrogen dioxide can irritate the mucous membranes and cause shortness of breath. Animal studies suggest that repeated exposure to elevated levels of nitrogen dioxide may contribute to the development of lung diseases such as emphysema. Nitrogen dioxide also contributes to the formation of ground-level ozone, which is a severe irritant and can cause coughing, choking, and stinging eyes.

Particulate matter, especially fine particulate matter (PM2.5), is another major health concern. These tiny solid particles and liquid droplets released by combustion can penetrate deep into the lungs and even enter the bloodstream, affecting multiple organs. Exposure to PM2.5 is linked to increased respiratory problems, decreased lung function, alterations in the body's defense systems, and premature mortality. It is also associated with chronic obstructive pulmonary disease, lung cancer, heart diseases, strokes, and other adverse health effects.

Additionally, combustion releases toxic pollutants such as polycyclic aromatic hydrocarbons (PAHs), radon, benzo(a)pyrene, sulfur dioxide, and volatile chemicals. These pollutants have been linked to various health issues, including cancer, respiratory illnesses, and cardiovascular diseases. Children are particularly vulnerable to the health risks associated with combustion pollutants, and exposure during early development can have long-lasting impacts on their health and cognitive abilities.

The health risks of combustion pollution are not limited to the local areas where combustion occurs. The emissions contribute to climate change, which further exacerbates health issues. Climate change can lead to extreme heat, natural disasters, and the spread of infectious diseases, impacting communities worldwide.

Environmental injustice

The combustion of fossil fuels, such as coal, oil, and natural gas, releases greenhouse gases, including carbon dioxide, contributing to climate change and environmental injustice. This process, utilized for electricity production, heating, transportation, and industry, has significant climate, environmental, and health costs. Notably, the combustion of gasoline, a widely used fossil fuel, produces about 19 pounds of carbon dioxide per gallon burned, with aviation and motor gasoline combustion contributing significantly to overall CO2 emissions.

The adverse effects of combustion-induced pollution disproportionately impact marginalized communities, particularly communities of color and low-income populations. This environmental injustice is evident in the higher exposure to particulate matter pollution experienced by Black and Hispanic Americans, with exposure levels 56% and 63% higher, respectively, than their contribution to pollution. Furthermore, systemic racism, segregation, and policies enacted by majority-white political institutions have exacerbated the vulnerability of these communities to environmental hazards. For instance, African Americans are more likely to reside near hazardous waste emission sites, such as oil refineries, polluted water sources, and areas contaminated with toxic chemicals.

The COVID-19 pandemic further highlighted the environmental injustice faced by Black Americans, who experienced a mortality rate twice as high as that of white Americans due to underlying health conditions exacerbated by pollution, such as asthma and heart disease. The higher susceptibility to pollution-induced health issues among Black Americans is a direct consequence of environmental racism, which has led to unfair housing policies and disinvestment in communities of color. Residential segregation has resulted in people of color being concentrated in neighborhoods that lack political and financial empowerment, making them more vulnerable to the impacts of climate change and environmental degradation.

Children, another vulnerable group, bear the brunt of the impacts of air pollution and climate change caused by combustion. According to the World Health Organization (WHO), children under five bear more than 40% of the burden of environmentally related diseases and over 88% of the burden of climate change, despite constituting only 10% of the global population. This injustice is further amplified by the fact that children did not create the problems they now face. The combustion of fossil fuels for household cooking, heating, and lighting also poses significant health risks, particularly in low- and middle-income countries, where severe burns and injuries are often linked to the use of inefficient and polluting devices.

To address these pressing issues of environmental injustice, it is crucial to acknowledge the historical context of systemic racism and the existence of "sacrifice zones" exploited by polluters. Empowering communities susceptible to environmental harms to advocate for themselves and make preferred solutions is essential. Additionally, investing in organizations led by BIPOC individuals working to mitigate environmental injustices at the grassroots level is a vital step toward creating a more equitable and sustainable future for all.

Regulatory efforts

One notable effort is the International Congress on Combustion By-Products and Their Health Effects, sponsored by organisations like the Superfund Research Program, National Institute of Environmental Health Sciences, and National Science Foundation. This congress provides a platform for interdisciplinary discussions among scientists, engineers, and policymakers to advance the understanding of combustion pollution and its health implications. The congress addresses topics such as the formation, conversion, control, and health effects of combustion by-products, including particulate matter, heavy metals, organic pollutants, and environmentally persistent free radicals.

At the governmental level, organisations like the US Environmental Protection Agency (EPA) play a crucial role in identifying and regulating combustion pollutants. The EPA has classified sources of air pollution from burning fuels into stationary and mobile sources. Stationary sources include boilers, furnaces, and gas turbines, while mobile sources consist of transport means with internal combustion engines, such as diesel and spark ignition engines. The EPA also recognises the impact of indoor combustion appliances, such as space heaters, gas ranges, and fireplaces, on air quality.

To mitigate the environmental and health risks associated with combustion, regulatory efforts have focused on several strategies. These include improving fuel refinement, adopting emissions reduction technologies, and exploring alternative solutions like electrification and hybrid systems. Additionally, there is a growing emphasis on individual actions, such as reducing car usage, carpooling, and transitioning to alternative modes of transportation like cycling and walking. For indoor air quality, regulatory measures may include improving ventilation in buildings, banning certain construction materials that emit volatile organic compounds (VOCs), and implementing higher standards for household and personal hygiene products.

While regulatory efforts have made strides in addressing combustion-caused pollution, the dynamic nature of the field and the ongoing advancements in technology present continuous challenges. Stakeholders must remain committed to sustainability efforts, interdisciplinary collaboration, and the implementation of evidence-based policies to effectively mitigate the environmental and health impacts of combustion pollution.

Frequently asked questions