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.
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.
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.
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.
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.