Car Engines: Air Polluters Under The Hood

Cars, trucks, buses, off-road vehicles and planes are all considered mobile sources of air pollution. The combustion of fossil fuels in car engines produces harmful gases and pollutants that are emitted directly into the air, causing significant health and environmental risks. This includes carbon monoxide, nitrogen oxides, particulate matter, benzene, formaldehyde, and diesel particulate matter. These emissions contribute to smog, global warming, and the depletion of the ozone layer, with adverse impacts on human health and the environment. While electric vehicles are becoming more common, the majority of cars still rely on fossil fuels, making them a major contributor to air pollution.

Vehicle exhaust

Carbon monoxide is a colorless, odorless, and poisonous gas that is formed by the combustion of fossil fuels. It can limit the blood's ability to transport oxygen and is harmful to human health. Nitrogen oxides are reddish-brown gases that irritate the lungs and eyes. They also contribute to the formation of ground-level ozone, which is a main ingredient in smog. Particulate matter is a mixture of solid particles and liquid droplets found in the air that can damage the lungs and enter the bloodstream.

Volatile organic compounds (VOCs) are pollutants emitted from vehicles that react with nitrogen oxides in the presence of sunlight to form ground-level ozone. VOCs include toxic air pollutants such as benzene, acetaldehyde, and 1,3-butadiene, which have been linked to different types of cancer. Greenhouse gases, such as carbon dioxide, are also emitted from vehicle exhaust and contribute to global climate change.

To reduce air pollution from vehicle exhaust, various measures have been implemented. The Environmental Protection Agency (EPA) has set standards for smog, soot, and other air pollutants, as well as created programs that promote investments in clean vehicle and engine technology. The federal Clean Air Act of 1990 requires the implementation of vehicle emission control programs, inspection and maintenance (I/M) emissions testing, and the development of databases to analyze emission data. Catalytic converters are also used to reduce toxic gases and pollutants in vehicle exhaust by catalyzing redox reactions.

Fossil fuels

The burning of fossil fuels, such as coal, gasoline, and diesel, is a significant source of air pollution. This includes the emission of fine particulate matter, known as PM 2.5, which includes soot and tiny airborne particles up to 2.5 microns in diameter. These particles are easily inhaled and can penetrate deep into the lungs, causing respiratory issues and other health problems. Research has linked exposure to PM 2.5 from burning fossil fuels to approximately 8.7 million premature deaths worldwide in 2018, with the highest tolls seen in China and India.

In addition to the direct emissions from combustion, the extraction and processing of fossil fuels also contribute to air pollution. For example, a 2017 study found that approximately 17.6 million Americans are exposed daily to toxic air pollution from active oil and gas wells, transport, and processing facilities. This includes pollutants such as benzene and formaldehyde, which have been linked to serious health issues, including childhood leukemia and cancer.

The impact of fossil fuel pollution disproportionately affects certain demographics, including children, older individuals, those on low incomes, and people of color. Children, especially those affected by malnutrition or born prematurely due to air pollution, are more vulnerable to the neurotoxic effects and are at a greater risk of developing health complications. Additionally, developing countries bear a more significant burden of environmentally-related diseases and the impacts of climate change.

The consequences of burning fossil fuels extend beyond air pollution and contribute to global warming and climate change. The high carbon content of fossil fuels, particularly coal, leads to the release of large amounts of carbon dioxide, a greenhouse gas, into the atmosphere. This contributes to rising global temperatures, melting glaciers, and increasing sea levels, threatening the sustainability and equity of our planet for future generations.

Carbon monoxide

Motor vehicle emissions, including carbon monoxide, account for about 70% of air pollution in large cities. This is more than double the amount of air pollution from heating sources. Vehicle exhaust affects air quality both near the Earth's surface and high in the atmosphere, contributing to smog and haze. The Environmental Protection Agency estimates that vehicles cause nearly 75% of carbon monoxide pollution in the United States.

To reduce air pollution from motor vehicles, the federal Clean Air Act of 1990 requires the implementation of vehicle emission control programs. This includes the use of catalytic converters, which reduce toxic gases and pollutants in exhaust gas through a redox reaction. Despite these efforts, carbon monoxide emissions from vehicles remain a significant concern, particularly for individuals who live or work in close proximity to busy roads.

Occupational exposure to carbon monoxide is a particular concern for individuals working in indoor car wash facilities in large shopping malls with closed parking lots. A study conducted on male car wash employees in Istanbul, Turkey, found that these individuals had higher blood levels of carboxyhemoglobin (COHb), indicating prolonged exposure to high levels of carbon monoxide from car exhaust emissions.

In addition to carbon monoxide, automobiles using gasoline produce methane and nitrous oxide, as well as hydrofluorocarbon from leaking air conditioners. The impact of these emissions is significant due to their high global warming potential. Electric vehicles, on the other hand, do not emit tailpipe emissions and are a more environmentally friendly alternative.

Nitrogen oxides

During combustion, nitrogen and oxygen in the air combine with hydrocarbons (gasoline, diesel, etc.) to produce carbon dioxide and water. However, in the real world, car manufacturers need to account for and reduce the production of unwanted by-products like NOx. One way to increase engine power is to produce more oxygen, allowing gas to burn quicker and resulting in more power. However, this also increases the production of NOx.

Diesel engines, which tend to have better fuel efficiency, operate at higher temperatures and pressures than petrol engines. This increases the volatility of combustion, leading to stronger and more abundant NOx emissions. While petrol engines produce NOx as well, it is not to the same extent as diesel engines.

NOx emissions from vehicles have been regulated since the 1960s. One critical method for reducing NOx in cars is through the use of exhaust gas recirculation (EGR). This process redirects exhaust gas from the engine back into the engine cylinder, reducing the amount of oxygen and the temperature to produce fewer emissions. Another method is to use a catalytic converter, which reduces NOx to nitrogen and water and/or carbon dioxide.

Smog

Cars, trucks, buses, off-road vehicles, and planes are all considered mobile sources of air pollution. The combustion of fossil fuels, such as gasoline and diesel, in internal combustion engines is a major contributor to air pollution. This process involves burning fuel inside an engine, which gives off heat and produces gases that are released through the vehicle's tailpipe. These emissions contain pollutants such as nitrogen oxides, particulate matter, carbon monoxide, and volatile organic compounds (VOCs).

Nitrogen oxides (NOx) are formed during the combustion of fossil fuels and contribute to the formation of ground-level ozone, a major ingredient in smog. Ground-level ozone irritates the respiratory system, causing coughing, choking, and reduced lung capacity. It is especially harmful to individuals with asthma and young children.

Particulate matter, a mixture of solid particles and liquid droplets, is another pollutant emitted by vehicles. It contributes to atmospheric haze and can damage the lungs and enter the bloodstream. Additionally, VOCs emitted from vehicles include toxic air pollutants such as benzene, acetaldehyde, and 1,3-butadiene, which have been linked to different types of cancer.

The Environmental Protection Agency (EPA) estimates that vehicles are responsible for nearly 75% of carbon monoxide pollution in the United States. Carbon monoxide is a colorless, odorless, and poisonous gas that forms when fossil fuels are burned. It can limit the blood's ability to transport oxygen, posing significant health risks.

To address these issues, the EPA has implemented standards and programs to reduce emissions and improve air quality. This includes surveillance testing of vehicles, engines, and fuels, as well as investments in clean vehicle and engine technology. By 2030, the EPA projects that their air quality emissions standards for vehicles will prevent significant amounts of smog, soot, and other air pollutants, leading to improved public health.

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