Vehicle Emissions: Understanding Air Pollution Sources

Vehicles are a major contributor to air pollution, which has significant health and environmental risks. Cars, trucks, and buses powered by fossil fuels emit pollutants such as carbon dioxide, carbon monoxide, nitrogen oxides, and particulate matter, which are harmful to human health and the environment. These emissions contribute to global climate change, the formation of acid rain, and the creation of secondary pollutants such as ground-level ozone, a common component of smog. While newer vehicles generally emit less pollution, the increasing number of vehicles on the road and traffic congestion continue to have a significant impact on air quality, particularly in urban areas and near major highways.

Carbon monoxide

The combustion of gasoline in vehicle engines results in the formation of carbon monoxide, which is released through the tailpipe. The level of emissions can vary depending on factors such as the vehicle's fuel type, fuel economy, and mileage. Older vehicles tend to emit more pollution, while newer models generally produce less pollution due to improved emission control technology and stricter emission standards.

The impact of carbon monoxide pollution from vehicles is more pronounced in urban areas, particularly near major highways, where traffic congestion leads to higher concentrations of this harmful gas. Additionally, certain weather conditions, such as very hot or cold temperatures, can influence the emission rates of carbon monoxide.

To address the issue of carbon monoxide pollution from vehicles, governments have implemented stricter emission standards and encouraged the adoption of alternative fuel sources and electric vehicles. These efforts aim to reduce the environmental and health impacts associated with carbon monoxide and other tailpipe emissions.

While carbon monoxide pollution from vehicles contributes significantly to overall air pollution, it is important to note that indoor environments or enclosed spaces can also have elevated levels of carbon monoxide, which may pose more immediate health risks.

Nitrogen oxides

NOx is a mixture of nitric oxide (NO), which is harmless, and nitrogen dioxide (NO2). NOx emissions have been regulated since the 1960s. However, in 2015, Volkswagen was found to be deliberately manipulating the performance of diesel cars' emissions control systems to "defeat" vehicle tests that certify a car's NOx pollution levels. Since then, evidence has emerged that most, if not all, diesel manufacturers in Europe have used legal or possibly illegal strategies to circumvent vehicle emissions tests.

NOx emissions have been linked to adverse impacts on nearly every organ system in the body. They are harmful as a primary pollutant, causing lung irritation and weakening the body's defences against respiratory infections such as pneumonia and influenza. They also contribute to the production of ground-level ozone and fine particulate matter (PM2.5), which are two of the most notorious pollutants that can impact human health. NO2 is also responsible for aggravating cardiovascular and respiratory disease.

To reduce NOx emissions, combustion temperatures can be lowered, and aftertreatment devices can be used to cause a chemical reaction that reduces NOx in the exhaust to nitrogen and water and/or CO2. In addition, zero-emission heavy-duty vehicles, electric cars, and alternative fuels can help reduce NOx emissions.

Volatile organic compounds

Cars, trucks, and buses powered by fossil fuels are major contributors to VOCs in the air. In fact, transportation emits more than half of the nitrogen oxides in our air, and is a major source of heat-trapping emissions. VOCs emitted from cars, trucks, and buses include toxic air pollutants such as benzene, acetaldehyde, and 1,3-butadiene, which are linked to different types of cancer.

The health impacts of VOCs include eye, nose, and throat irritation, headaches, nausea, dizziness, and difficulty breathing. Long-term exposure can damage the liver, kidneys, and central nervous system. VOCs may also worsen symptoms for people with asthma and COPD. Concentrations of VOCs indoors are up to 10 times higher than outdoors, and studies have found that levels of organics average 2 to 5 times higher indoors than outdoors. During and for several hours after certain activities, such as paint stripping, levels may be 1,000 times higher than outdoor levels.

To reduce exposure to VOCs, it is recommended to use products that are low in VOCs, read product labels, avoid or limit the use of items with harmful ingredients, safely dispose of unwanted products, and increase ventilation when using products containing VOCs. Electric cars and alternative fuels can also help to reduce VOC emissions from vehicles.

Particulate matter

Vehicles, including cars, trucks, buses, and other heavy-duty vehicles, contribute significantly to particulate matter pollution, particularly in urban areas and near major highways. The combustion of fossil fuels, such as gasoline and diesel, in vehicle engines releases particulate matter into the atmosphere. In addition, particulate matter can also form as a secondary pollutant from other vehicle emissions, such as nitrogen oxides (NOx).

The health impacts of particulate matter exposure are well-documented. Studies have linked PM2.5 exposure to various diseases of the pulmonary, cardiac, vascular, and neurological systems. These include acute lower respiratory illness, cerebrovascular disease, ischaemic heart disease, chronic obstructive pulmonary disease, and lung cancer. According to the US Environmental Protection Agency (EPA), transportation is responsible for a significant portion of PM2.5 emissions, with on-road vehicles being a primary source.

The impact of particulate matter pollution from vehicles is particularly evident in urban areas with high traffic congestion. For example, a study in New York City found that air pollutant emissions from on-road vehicles contributed to hundreds of preventable PM2.5-attributable deaths, hospitalizations, and emergency department visits among residents. Additionally, the study highlighted the disproportionate impacts on high-poverty neighbourhoods, underscoring the need for targeted policy interventions.

While electric vehicles, such as electric cars, trucks, and buses, offer a promising solution to reducing particulate matter emissions, their adoption rate needs to accelerate to make a substantial impact. In the meantime, individuals can play a role in reducing their exposure to particulate matter by driving less, carpooling, or using public transportation whenever possible. Additionally, keeping windows closed and using the recirculation mode while driving can significantly reduce in-car PM2.5 concentrations.

Global warming

Motor vehicles are a significant contributor to air pollution. Burning gasoline and diesel fuel creates harmful byproducts, including nitrogen dioxide, carbon monoxide, hydrocarbons, benzene, and formaldehyde, and carbon dioxide, the most common human-caused greenhouse gas. Greenhouse gas emissions from transportation account for about 28% of total US greenhouse gas emissions, making it the largest contributor to US emissions. In 2019, mobile sources constituted 32% of total anthropogenic greenhouse gas emissions in the US, including emissions from non-transportation sources.

The buildup of carbon dioxide and other greenhouse gases, such as methane, nitrous oxide, and hydrofluorocarbons, is causing the Earth's atmosphere to warm, leading to climate change. This warming results in rising average global temperatures, causing sea levels to rise, increasing the frequency and intensity of natural disasters, and leading to other domino effects. For example, global warming is causing more frequent and intense heat waves, sea level rise, flooding, drought, and wildfires that can devastate communities. People in low-income communities and communities of color are disproportionately exposed to higher levels of air pollution.

To address this issue, individuals can choose to drive the most fuel-efficient vehicle that meets their needs, reduce the number of miles driven, and observe speed limits. Electric vehicles, for instance, emit no harmful tailpipe pollution and have significantly lower global warming emissions than vehicles powered by fossil fuels. Additionally, carpooling, walking, or biking can help reduce pollution and save money.

On a broader scale, the EPA and other organizations are implementing programs and policies to reduce greenhouse gas emissions from the transportation sector. These include improving fuel efficiency, promoting the use of low-carbon fuels, and developing new vehicle technologies. The SmartWay program helps the freight transportation sector improve supply chain efficiency, reduce greenhouse gases, and save fuel costs. The EPA also provides resources like the Green Vehicle Guide to help consumers identify more efficient and less polluting vehicles.

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