Bronte Wells
Cars are a major contributor to air pollution and the health consequences it causes worldwide. The combustion of fuels such as gasoline, diesel fuel, and fuel oil releases exhaust gases, which are emitted through the exhaust pipe of vehicles. These gases often contain harmful pollutants, including nitrogen oxide, carbon monoxide, hydrocarbons, and particulate matter. While water vapour and carbon dioxide are also present in exhaust gases, they are not considered toxic. However, carbon dioxide is a significant contributor to climate change, and motor vehicles generate about 20% of the European Union's man-made carbon dioxide emissions. In addition to exhaust fumes, brake and tyre wear also contribute to harmful emissions, even in electric cars.
| Characteristics | Values |
|---|---|
| Major Pollutants | Nitrogen oxide, carbon monoxide, hydrocarbons |
| Other Pollutants | Benzene, black carbon, nitrogen dioxide, water vapour, soot, dust, plastic particles, ozone |
| Health Risks | Asthma, heart disease, allergies, skin irritation, eye irritation, respiratory problems, lung cancer |
| Environmental Risks | Global warming, climate change, smog, decrease in oxygen, increase in carbon dioxide |
| Emission Sources | Petrol and diesel vehicles, brakes, tyres, power plants, off-road equipment |
| Emission Reduction Methods | Catalytic converters, diesel particulate filters, improved engine and exhaust design, clean air zones, emission standards, alternative fuels |
| Emission Statistics | Motor vehicles generate ~20% of EU's man-made CO2 emissions; 53,000 early deaths/year in the US; 98-99% cleaner cars today vs 1960s |
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What You'll Learn
Particulate matter, soot and metal particles
Particulate matter, soot, and metal particles are among the most harmful components of automobile exhaust. These emissions are particularly associated with diesel engines, which emit airborne particles of black soot and metal, known as particulate matter.
Particulate matter, in the context of automobile emissions, refers to the collected matter on a flow-through filter under specific conditions. These particles can be divided into volatile and non-volatile (or solid) categories, depending on the conditions at the tailpipe, which are high temperature and high concentration. However, some species that appear volatile at tailpipe conditions may become semi-volatile at atmospheric conditions, as they transition to the particulate phase at low temperatures.
Diesel particulate matter (DPM) or diesel exhaust particles (DEP) are the particulate components of diesel exhaust. These include diesel soot, aerosols, ash particulates, metallic abrasion particles, sulfates, and silicates. DPM can take the form of individual particles or chain aggregates, mostly in the invisible sub-micrometer range of 100 nanometers, known as ultrafine particles or PM0.1. The fine particles in diesel exhaust are of particular concern as they can penetrate deep into the lungs when inhaled. The polycyclic aromatic hydrocarbons (PAHs) in the exhaust irritate the lungs, causing coughing, wheezing, and shortness of breath. Moreover, the rough surfaces of these particles make them more likely to bind with other toxins in the environment, increasing the hazards of inhalation.
Modern diesel cars are often fitted with diesel particulate filters (DPFs) to capture carbon particles and prevent them from being released into the atmosphere. These filters work by burning the captured particles using extra fuel injected directly into the filter. While this process prevents carbon buildup, it comes at the cost of wasting a small amount of fuel. Additionally, SCR systems, which do not require particulate matter (PM) filters, can improve fuel efficiency by 3-5% when combined with SNCR filters.
It is important to note that particulate matter is not only released from exhaust fumes but also from brake and tyre wear. These particles, including dust and plastic particles, can enter the airstream and have damaging effects on human health and the environment. Upcoming Euro 7 emission standards will address this issue by implementing official brake and tyre emission limits.
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Nitrogen oxide, carbon monoxide, and hydrocarbons
Nitrogen oxide (NOx) is produced in any combustion process and is highly reactive. When NOx and volatile organic compounds (VOCs) react in the presence of sunlight, ground-level ozone is formed, which is a primary ingredient in smog. Smog is a major issue in some large cities, causing air pollution and negative health impacts on residents.
Carbon monoxide (CO) is a toxic and invisible gas that is the result of incomplete combustion of fuel. It is very harmful to humans and can cause headaches, respiratory problems, and even death if inhaled in large quantities. Older engines tend to produce higher amounts of CO compared to modern engines, which have more efficient combustion processes.
Hydrocarbons (HCs) escape from exhausts as unburnt fuel due to incomplete combustion. They also evaporate from the fuel tank and nozzle during the refuelling process. HCs are formed in the quench area of the exhaust system.
In addition to these major pollutants, other harmful emissions from automobiles include particulate matter, such as black soot and metal particles, released by diesel engines. Brakes and tyres also contribute to harmful emissions, releasing tiny fragments of particulate matter such as dust into the air.
To mitigate these issues, advancements in technology and policies to combat climate change have helped reduce emissions. Catalytic converters and particulate filters are now standard on new petrol and diesel cars, and many cities have implemented clean air zones to restrict the entry of highly polluting vehicles.
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Health risks of living near highways
Exhaust gases from automobiles are a major source of air pollution, with over 1.45 billion petrol and diesel vehicles on the road globally. These vehicles emit harmful gases and particles, such as nitrogen oxides, carbon monoxide, volatile organic compounds, and particulate matter, which can have detrimental effects on human health.
Living near highways, where exposure to these pollutants is heightened, poses several health risks. Firstly, residents are at an increased risk of developing respiratory problems. Inhaling pollutants from vehicle exhaust fumes can lead to allergies, skin irritation, and respiratory issues such as asthma. Additionally, the particulate matter and toxic particles emitted from diesel trucks and brake dust can exacerbate respiratory conditions and increase the risk of lung cancer, as reported by the World Health Organization.
Secondly, cardiovascular health is also at risk for those living in close proximity to highways. The pollutants from automobile exhaust have been linked to an elevated risk of heart disease. Furthermore, the proximity to busy roads and traffic density increases the likelihood of developing cardiovascular conditions, as evidenced by studies in California.
The health risks extend beyond respiratory and cardiovascular issues. Living near highways has been associated with reproductive health problems and endocrine conditions. People of color, those experiencing linguistic isolation, and those without insurance are more likely to be exposed to higher levels of traffic pollution, making NRAP (near-roadway air pollution) an environmental justice concern.
It is important to note that factors beyond distance from the highway influence the health risks. Wind patterns, freeway design, time of day, and the types of vehicles and buildings nearby also play a role in determining the pollution levels and, consequently, the health outcomes for residents. Nevertheless, living near multiple pollution sources, such as highway interchanges and freeway ramps, significantly increases the health risks associated with air pollution.
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Carcinogenic substances and health problems
The major pollutants from automobile exhaust are nitrogen oxide, carbon monoxide, and hydrocarbons. These are formed during the combustion of fuels such as natural gas, gasoline, diesel fuel, fuel oil, biodiesel blends, or coal. The exhaust gas or flue gas is discharged into the atmosphere through an exhaust pipe, a flue gas stack, or a propelling nozzle.
The increasing number of motor vehicles on the road has led to greater exposure to their exhausts, which contain a complex mixture of hundreds of chemical compounds. Many of these compounds are harmful and cause chronic irritation of the respiratory mucosa, while some are carcinogenic, particularly polycyclic aromatic hydrocarbons (PAHs) and nitroarenes. PAHs are present in the particulate phase of gasoline-engine exhausts, and both the gas and soot portions of diesel exhaust contain PAHs.
The US Environmental Protection Agency (EPA) classifies diesel exhaust as "likely to be carcinogenic to humans". The National Institute for Occupational Safety and Health (NIOSH) also considers diesel exhaust a "potential occupational carcinogen". Several studies have found a possible link between diesel exhaust and lung cancer, and exposure to diesel exhaust has been associated with an increased risk of lung cancer. Other studies have investigated links between diesel exhaust and cancers of the bladder, larynx, esophagus, stomach, and pancreas, as well as blood system cancers such as lymphomas and leukemias, but more research is needed to confirm these potential links.
In addition to the carcinogenic risks, pollutants from car exhausts are linked to a range of other health problems, including allergies, skin irritation, heart disease, and respiratory problems such as asthma. The World Health Organization has stated that long-term repeated exposure to diesel exhaust fumes may increase the risk of lung cancer.
Air pollution from fossil fuel use, including vehicle emissions, is estimated to cause over 5 million premature deaths each year globally. In the United States alone, 53,000 early deaths per year are attributed to vehicle emissions, according to a 2013 study by the Massachusetts Institute of Technology (MIT). Similarly, a study by the same university found that traffic fumes cause 5,000 premature deaths annually in the United Kingdom.
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Climate change and emission standards
The major pollutants from automobile exhaust are nitrogen oxide, carbon monoxide, and hydrocarbons, benzene, particulate matter, and water vapour. These emissions contribute to air pollution and global greenhouse gas emissions. Motor vehicles are calculated to generate about 20% of the European Union's man-made CO2 emissions, with passenger cars contributing about 12%.
To tackle this issue, emission standards have been implemented by various regulatory bodies and governments worldwide. For example, the European Union has set emission standards to limit the CO2 emissions of new passenger cars and light vehicles. These standards have resulted in a decrease in average new car CO2 emissions. Additionally, many cities have introduced clean air zones to discourage the most polluting vehicles from entering.
In the United States, the Environmental Protection Agency (EPA) has played a significant role in addressing climate change and emission standards. The EPA has implemented CO2 emission standards for airplanes and large business jets, consistent with international standards. The EPA has also proposed standards for heavy-duty vehicles to reduce greenhouse gas emissions, starting in model year 2027. However, there has been controversy surrounding the EPA's stance on carbon dioxide, with some arguing that the agency is gutting its greenhouse gas rules.
The Global Reporting Initiative (GRI) has also been active in the area of climate change and emission standards. The GRI has developed standards and disclosures on climate-related issues, aiming to incorporate new issues and create transparency in climate reporting. The GRI Standards are designed to align with the latest developments and intergovernmental instruments in the field of climate change and greenhouse gas emissions.
Overall, the issue of climate change and emission standards is a complex and ongoing challenge. While efforts have been made to reduce emissions and mitigate the impact of climate change, there is still much work to be done. Regulatory bodies, governments, and organizations continue to play a crucial role in establishing and enforcing standards to address this global issue.
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Frequently asked questions
The major pollutants from automobile exhaust are nitrogen oxide, carbon monoxide, and hydrocarbons. These are formed when fuel burns, causing nitrogen and oxygen to react and form nitrogen oxides.
People who live near busy roads or major highways are at significant risk of developing health problems linked to air pollution. According to the World Health Organization, long-term exposure to diesel exhaust fumes may increase the risk of lung cancer. Other health issues include allergies, skin irritation, heart disease, and respiratory problems such as asthma.
There are several ways to reduce automobile exhaust emissions:
- Using alternative modes of transportation like walking, biking, carpooling, or taking public transportation.
- Adopting hybrid or electric cars, which have lower emissions.
- Improving fuel efficiency and engine and exhaust system design.
- Implementing catalytic converters and particulate filters in vehicles.
- Establishing clean air zones that discourage highly polluting vehicles from entering certain areas.
