Cars and Air Pollution Air Division Planning & Air Quality Analysis Branch Tony Davis, Branch Manager - (501) 682-0767

Cars and Air Pollution

According to the EPA, in typical urban areas cars, buses, trucks, and off-highway mobile sources such as construction vehicles and boats produce at least half of the hydrocarbons and nitrogen oxides. Even though nationally these pollutants are created from a great variety of industrial and combustion processes, the personal automobile is the single greatest polluter.

Many people typically associate air pollution with the billowing smokestacks of large industries.  Air pollution emissions from each individual car are generally small.  America's population of automobiles & drivers are increasing.  This combined with the traffic congestion of urban areas results in a very large amount of air pollution.  The emissions from the millions of vehicles on our nations roads each day contribute substantially to our air pollution problems.  Driving a private car is probably a typical citizen's most "polluting" daily activity.

The power to move a car comes from burning fuel in an engine. Pollution from cars comes from by-products of this combustion process (exhaust) and from evaporation of the fuel itself.

While ozone is not emitted directly from automobiles, the unstable compound is formed in the atmosphere through a complex set of chemical reactions involving hydrocarbons, oxides of nitrogen, and sunlight. The rate at which the reactions proceed is related to both temperature and intensity of the sunlight. Because of this, problematic ozone levels occur most frequently on hot summer afternoons.

When ADEQ issues an Ozone Advisory or Alert, we suggest certain voluntary actions to help reduce ozone formation:

• Limit automobile use by carpooling, walking or riding the bus.
• Avoid driving during congested "rush hour" traffic and at lunchtime.
• Postpone or combine errands.
• Replace face-to-face meetings with conference calls.
• If possible, telecommute and participate in flextime or compressed-work-weeks.
• Keep your car well tuned and avoid jackrabbit starts and excessive idling.
• Avoid use of oil-based paints and solvents.
• Refuel motor vehicles and mow lawns during the late afternoon or evening hours only.

The majority of these suggested voluntary actions relate to how you drive your vehicle. To help you better understand the significant amount of positive influence that you can have on Arkansas Air Quality, we have provided some interesting information.

Commuter Calculator  This tool will allow you to perform a cost analysis of your weekly driving routines. By entering a few facts about how many miles you drive, the fuel efficiency of your vehicle and the price of fuel, you are provided with daily, monthly and yearly cost totals. By carpooling, even with just one other person, the potential financial savings are quickly calculated for you. If you add more members to the car pool, you can increase your savings even more!

Green Vehicle Guide  This guide will help you choose the cleanest and most fuel-efficient vehicle that meets your needs.  The EPA website will help consumers make more environmentally-informed choices when purchasing a vehicle.  The Green Vehicle Guide lists pollution levels for all recent model year passenger vehicles sold in the United States. Consumers can select a vehicle model, determine how clean it is relative to other vehicles, comparison shop for similar vehicles, and choose the cleanest vehicle that meets their needs.

Pounds of Pollution¹

Air pollution is a difficult concept to grasp. While we often can't see air pollution, automobiles create many different kinds of emissions. Air pollution is often referred to in terms of pounds. You know that air has weight, but how much of a gas is a pound?

If you use your chemistry and math skills to complete this activity, you will be able to provide a interesting visual display to others and help to raise awareness about air pollution.

Objectives:

• To calculate the weight of various pollutants
• To visualize the amount of air pollution emitted by a car each year

Materials:

• Many 2-liter soda bottles

Procedure:

A. Calculate the volume of 1 pound of whatever air pollutant you are interested in by using the following equation:

454g	x	1 mole	x	22.4L	= liters of gas/pound *
1 lb.		"X"g		1 mole

B. Calculate how many 2-liter bottles are needed for the display. Use the following equation:

volume of 1 lb. of the pollutant	= total bottles**
2 liters

Explanation:

*A. There are 454 grams in a pound. The first step is to find out how many grams of the chosen pollutant are in a mole. This number can be calculated using values from the Periodic Table of Elements. (Clickable online version)  Add the grams per mole for each compound. For example, one atom of oxygen is 16 grams per mole and carbon is 12 grams per mole. This totals 44 grams per mole of carbon dioxide molecule. (CO₂ is 2 oxygen atoms plus 1 carbon atom.) For your convenience, we have listed the weights of carbon dioxide, carbon monoxide, and nitrogen dioxide, three pollutants given off by cars. Insert these values for "X" depending on the pollutant:
      CO₂ = 44g       CO = 28g       NO₂ = 46g

There are 22.4 liters in a mole. Multiply by this number of liters and you have converted the pound of gas into an equivalent number of liters.

**B. For example, if you are dealing with CO₂, which you have calculated to be 231 liters per pound, divide 231 by 2. This tells you that you need 115.5 two-liter bottles to represent one pound of CO₂.

Answer:  Number of 2-liter bottles:

CO2 = 115.5 bottles CO = 181.5 bottles NO2= 110.5 bottles

Emission Facts: Average Annual Emissions and Fuel Consumption for Passenger Cars and Light Trucks

EPA420-F-00-013, April 2000

Download PDF version formatted for print (3 pp, 24K, About PDF Files)
The figures presented in this document are averages only. Individual vehicles may differ in miles traveled and pollution emitted per mile than indicated here. Emission rates and fuel consumption totals may differ slightly from original sources due to rounding.

Background

The emission rates for hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) shown in the following tables are from U.S. Environmental Protection Agency (EPA) highway vehicle emission factor models. They assume an average, properly maintained vehicle on the road in July 2000, operating on typical gasoline on a warm summer day (72-96 degrees F). Emissions may be higher in very hot (especially HC) or very cold (especially CO) weather.

The calculations for Total Annual Pollution Emitted and Fuel Consumed are based on an average annual passenger car mileage of 12,500 miles and an average annual light truck mileage of 14,000 miles. Fuel consumption is based on fleetwide average in-use fuel economy of 21.5 miles per gallon (mpg) for passenger cars and 17.2 mpg for light trucks, as reported in the 19th edition of the "Transportation Energy Data Book," prepared for the U.S. Department of Energy.

Notes

1. These emission factors and fuel consumption rates are averages for the entire in-use fleet. Newer cars and trucks will emit less pollution and use less gasoline; older cars and trucks may emit more pollution and use more gasoline.
2. Carbon dioxide, while not regulated as an emission, is the transportation sector's primary contribution to climate change. Carbon dioxide emissions are directly proportional to fuel economy--each 1% increase (decrease) in fuel consumption results in a corresponding 1% increase (decrease) in carbon dioxide emissions.
3. The total annual emissions and fuel consumption are greater for light trucks than was presented in the April 1998 version of this fact sheet. This reflects the increasing trend toward the largest, heaviest light trucks, which currently and in the past have had less stringent emission standards and lower fuel economy than do the lighter light trucks and cars. The new "Tier 2" emission standards taking effect starting with the 2004 model year will bring all light trucks into compliance with the same emission standards as cars (for HC, CO, and NOx).

For More Information

You can access many additional documents on emissions and fuel consumption of passenger cars and light trucks electronically from the Office of Transportation and Air Quality Web site at: http://www.epa.gov/otaq

You can also contact the National Vehicle and Fuel Emission Laboratory library for document information, by mail or phone at:

U.S. Environmental Protection Agency
Office of Transportation and Air Quality
NVFEL Library
2000 Traverwood Drive
Ann Arbor, MI 48105
(734) 214-4311

Want more information about cars and pollution? Check out these EPA fact sheets.

• U.S. EPA's Office of Transportation and Air Quality (OTAQ)
• Particulate Matter Description & Trends

¹ Adapted with permission from the 1995 Wisconsin Dept. of Natural Resources "Where's the Air" Study Guide.