U.S. EPA Office of Air Quality Planning and Standards

Publication

The Plain English Guide To The Clean Air Act

Mobile sources (cars, trucks, buses, off-road vehicles, planes, etc.)

Each of today's cars produces 60 to 80 percent less pollution than cars in the 1960s. More people are using mass transit. Leaded gas is being phased out, resulting in dramatic declines in air levels of lead, a very toxic chemical.

Despite this progress, most types of air pollution from mobile sources have not improved significantly.

At present the United States:

Motor vehicles are responsible for up to half of the smog-forming VOCs and nitrogen oxides (NOx).
Motor vehicles release more than 50 percent of the hazardous air pollutants.
Motor vehicles release up to 90 percent of the carbon monoxide found in urban air.

What went wrong?

More people are driving more cars more miles on more trips. In 1970, Americans traveled 1 trillion miles in motor vehicles, and we are expected to drive 4 trillion miles each year by 2000.
Many people live far from where they work; in many areas, buses, subways, and commuter trains are not available. Also, most people still drive to work alone, even when van pools, HOV (high-occupancy vehicle) lands and other alternatives to one-person-per-car commuting are available.
Buses and trucks, which produce a lot of pollution, haven't had to clean up their engines and exhaust systems as much as cars.
Auto fuel has become more polluting. As lead was being phased out, gasoline refiners changed gasoline formulas to make up for octane loss, and the changes made gasoline more likely to release smog-forming VOC vapors into the air.

Although cars have had pollution control devices since the 1970s, the devices only had to work for 50,000 miles, while a car in the United States is usually driven for 100,000 miles.

The 1990 Clean Air Act takes a comprehensive approach to reducing pollution from motor vehicles. The Act provides for cleaning up fuels, cars, trucks, buses and other motor vehicles. Auto inspection provisions were included in the law to make sure cars are well maintained. The 1990 law also includes transportation policy changes that can help reduce air pollution.

Cleaner fuels

It will be very difficult to obtain a significant reduction in pollution from motor vehicles unless fuels are cleaned up. The 1990 Clean Air Act will clean up fuels. The phaseout of lead from gasoline will be completed by January 1, 1996. Diesel fuel refining must be changed so that the fuels contain less sulfur, which contributes to acid rain and smog.

Gasoline refiners will have to reformulate gasoline sold in the smoggiest areas; this gasoline will contain less volatile organic compounds (VOCs) such as benzene (which is also a hazardous air pollutant that causes cancer and aplastic anemia, a potentially fatal blood disease). Other polluted areas can ask EPA to include them in the reformulated gasoline marketing program. In some areas, wintertime carbon monoxide (CO) pollution is caused by people starting their cars. In these areas, refiners will have to sell oxyfuel, gasoline with oxygen added to make the fuel burn more efficiently, thereby reducing carbon monoxide release.

All gasolines will have to contain detergents, which, by preventing build-up of engine deposits, keep engines working smoothly and burning fuel cleanly. Low VOC, oxyfuel and detergent gasolines are already sold in several parts of the country.

The 1990 Clean Air Act encourages development and sale of alternative fuels such as alcohols, liquefied petroleum gas (LPG) and natural gas.

Gas stations in smoggy areas will install vapor recovery nozzles on gas pumps. These nozzles cut down on vapor release when you put gas in your car.

Cleaner cars

The 1990 Clean Air Act requires cars to have under-the-hood systems and dashboard warning lights that check whether pollution control devices are working properly. Pollution control devices must work for 100,000 miles, rather than the current 50,000 miles. Auto makers must build some cars that use clean fuels, including alcohol, and that release less pollution from the tailpipe through advanced engine design. Electric cars, which are low-pollution vehicles, will also be built. Since California, especially southern California, has the worst smog problems, manufacturers will first sell clean fuel cars in a pilot project in California. By 1999, at least 500,000 of these clean fuel cars are to be manufactured for sale in California each year. Other states can require that cars meeting the California standards be sold in their states.

Many companies and government agencies have fleets of cars. Fleet-owners in very smoggy areas must buy the new cleaner cars starting in the late 1990s.

Inspection and maintenance (I/M) programs

Under the 1990 Clean Air Act, auto manufacturers will build cleaner cars, and cars will use cleaner fuels. However, to get air pollution down and keep it down, a third program is needed; vehicle inspection and maintenance (I/M), which makes sure cars are being maintained adequately to keep pollution emissions (releases) low. The 1990 Clean Air Act includes very specific requirements for inspection and maintenance programs.

Before the 1990 Clean Air Act went into effect, seventy United States cities and several states already had auto emission inspection programs. The 1990 law requires inspection and maintenance programs in more areas: forty metropolitan areas, including many in the northeastern United States, are required to start emission inspection and maintenance programs.

Some areas that already have inspection and maintenance programs are required to enhance (improve) their emission inspection machines and procedures. Enhanced inspection and maintenance machines and procedures will give a better measurement of the pollution a car releases when it is actually being driven, rather than just sitting parked at the inspection station. Enhanced inspection and maintenance programs may result in changes in where cars are inspected in your local area. Since the enhanced emission inspection and maintenance machines are expensive, some of the private stations now conducting inspection and maintenance programs may not want to buy the enhanced machinery. But the added expense for the new machinery will be more than made up for by air pollution reductions: emission inspection and maintenance programs are expected to have a big payoff in reducing air pollution from cars.

Cleaner trucks and buses

Starting with model year 1994, engines for new big diesel trucks will have to be built to reduce particulate (dust, soot) releases by 90 percent. Buses will have to reduce particulate releases even more than trucks. To reduce pollution, companies and governments that own buses or trucks will need to buy new clean models. Small trucks will be cleaned up by requirements similar to those for cars.

Non-road vehicles

Locomotives, construction equipment and even riding mowers may be regulated under the 1990 Clean Air Act. Air pollution from locomotives must be reduced. For the other non-road vehicles, EPA must issue regulations if a study shows that controls would help cut pollution.

Transportation policies

The smoggiest metropolitan areas will have to change their transportation policies to discourage unnecessary auto use, and to encourage efficient commuting (van pools, HOV [high-occupancy vehicle] lanes, etc.). States carrying out the 1990 Clean Air Act may add surcharges to parking fees.