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Wednesday, December 4, 2013

Types of Air Pollution Caused by Cars


By Brett Smith, December 4, 2013

While motor vehicles are a necessity of modern life, they are a significant source of air pollution. Some of the compounds released by combustion engines, such as sulfur dioxide, can have severe health effects after just a short exposure period. Other pollutants, such as carbon dioxide, can take decades to have a cumulative, yet significant effect on the environment.

Greenhouse Gases

According to the EPA, 28 percent of all greenhouse gas emissions in the United States for 2011 were from transportation sources. Out of these emissions -- about half were from cars and light trucks.
The amount of carbon dioxide emitted per gallon of fuel used depends on its carbon content. While there is some variation among the different types of fuels, the EPA generally uses 8,887 grams of carbon dioxide per gallon to estimate total emissions. In addition to carbon dioxide, cars also emit smaller amounts of the potent greenhouse gases methane and nitrous oxide.

Particulate Matter

Cars emit soot, dust and smoke, also referred to as fine particulate matter. Some of the particulate matter emitted by combustion engines measures around 2.5 micrometers in diameter and particles of this size can lodge deep in the lungs. This type of pollution has been linked to lung cancer, asthma and cardiovascular problems.
From 2000 to 2012, the national average for fine particular matter has decreased by 33 percent, according to EPA statistics. The federal agency relies heavily on state, tribal and local agencies to track national and regional air quality trends. Under the Clean Air Act, each state is responsible for enacting a program to reduce particulate pollution in accordance with national standards.

Sulfur Dioxide

While not a significant source of sulfur dioxide, combustion engines do contribute to the atmospheric concentration of the caustic compound. According to EPA statistics from 2008, "mobile" sources represent about 6.7 percent of total American sulfur-dioxide emissions.
Short-term exposure to sulfur dioxide can result in a range of adverse respiratory effects, such as constriction of the lung's airways and heightened asthma symptoms. Sulfur dioxide can also react to form small particles that can become trapped deep within the lungs and cause conditions such as emphysema and bronchitis.

Air toxins

The combustion engines in cars can also release hazardous chemicals that are considered air toxins. These chemical include benzene, acetaldehyde and 1,3-butadiene. While benzene is a known carcinogen, acetaldehyde and 1,3-butadiene are suspected carcinogens, according to the EPA.
State and federal authorities have taken steps in recent years to require the reformulation of fuels in favor of eliminating these toxins. These steps are expected to reduce motor-vehicle-related air toxins more than 75 percent by 2020, compared to 1990 levels.