U.S. ENVIRONMENTAL PROTECTION AGENCY ERA 400^-92-013
OFFICE OF MOBILE SOURCES
Motor Vehicles and the 1990 Clean Air Act
Background
The Clean Air Act of 1970 set a national goal of clean and healthy air for all. It estab-
lished the first specific responsibilities for government and private industry to reduce
emissions from vehicles, factories, and other pollution sources. In many ways, the far-
reaching law has been a great success. Today's cars, for example, typically emit 70 to 90
percent less pollution over their lifetimes than their 1970 counterparts.
Despite considerable progress, the overall goal of clean and healthy air continues to
elude much of the country. Unhealthy air pollution levels still plague virtually every
major city in the United States. This is largely because development and urban sprawl
have created new pollution sources and have contributed to a doubling of vehicle travel
since 1970. Furthermore, scientists and now the public have become concerned about
previously unrecognized environmental threats such as global warming, acid rain and
air toxics.
With these issues in mind, Congress and the Administration in 1990 amended and
updated the Clean Air Act for the first time since 1977. The 1990 Clean Air Act includes
provisions to further control ground-level ozone (urban smog), carbon monoxide, and
particulate emissions from diesel engines and to address air toxics and acid rain. Motor
vehicles contribute to all these problems. This fact sheet focuses on the mobile source
provisions of the 1990 law, which together will reduce most vehicle-related pollutants by
more than 40 percent.
The 1990 Clean Air Act — What's New?
The new Clean Air Act strengthens components of the earlier law. The tailpipe stan-
dards for cars, buses, and trucks have been tightened, and Inspection and Maintenance
(I/M) programs have been expanded to include more areas and allow for more stringent
tests.
The 1990 law also introduces several entirely new concepts with regard to reducing
motor vehicle-related air pollution. For the first time, fuel is considered along with
vehicle technology as a potential source of emission reductions. And more attention is
focused on reducing the growth in vehicle travel. The new provisions include:
• Emphasis on Fuels
The act mandates that improved gasoline formulations be sold in some polluted cities
to reduce emissions of carbon monoxide or ozone-forming hydrocarbons. Other pro-
grams set low vehicle emission standards to stimulate the introduction of even
cleaner cars and fuels.
• Nonroad Engines
The 1990 Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to
FACT SHEET OMS-11.
August, 1994
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Motor Vehicles and CAA
consider emissions from off-highway vehicles as well as from highway vehicles such
as cars and trucks. The so-called "nonroad" category includes boats, farm equipment,
bulldozers, lawn and garden devices, and construction machinery. Because nonroad
engines have not been previously regulated for pollution, they can be very dirty. EPA
has determined that emissions from nonroad engines are a significant source of urban
air pollution and is working with industry and the public to develop effective control
strategies.
• Clean Transportation Alternatives
The law requires the smoggiest cities to limit growth in vehicle travel by encouraging
alternatives to solo driving. In areas where ozone levels exceed certain criteria,
employers of 100 or more will be asked to find ways to increase the average number of
passengers in each vehicle for commutes to work and during work-related driving
trips.
The 1990 Amendments: The View from the Driver's Seat
Typical drivers will probably not be aware of many vehicle and fuel changes manufac-
turers are making in response to the 1990 Clean Air Act, although these changes could
add $200 to the cost of a car and a few cents per gallon to the cost of gasoline. But there
are other programs that drivers will notice, especially in areas with air pollution prob-
lems.
New 1994 and later model cars must be equipped with "onboard diagnostic systems."
These systems feature dashboard warning lights that alert drivers to malfunctioning
emission control equipment. Controlled by the vehicle's computer, the onboard diagnos-
tic system must also be capable of storing trouble codes that help mechanics pinpoint
the malfunction.
Another change involves tampering and misfueling. Such activities have always been
discouraged, but were previously illegal only for commercial operations. "Backyard
mechanics" now are also subject to stiff penalties for deliberate tampering.
For drivers in polluted cities, more changes will be apparent. Some cities will have to
start I/M programs to check vehicle emissions on a regular basis. Areas that already
require I/M testing may have to institute more stringent programs.
A Summary of Some Specific Clean Air Act Programs
• Tighter Tailpipe Standards
Tailpipe (exhaust) standards for cars have been reduced under the 1990 law. The
previous standards of 0.41 gram per mile (gpm) total hydrocarbons, 3.4 gpm carbon
monoxide, and 1.0 gpm nitrogen oxides have been replaced with standards of 0.25
gpm nonmethane hydrocarbons and 0.4 gpm nitrogen oxides (the 3.4 gpm standard
for carbon monoxide does not change). These standards will be fully phased in with
1996 models. EPA is required to study whether even tighter standards are needed,
technologically feasible, and economical. If EPA determines by 1999 that lower
standards are warranted, the standards will be cut in half beginning with 2004 model
year vehicles.
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Motor Vehicles and CAA
• Carbon Monoxide Control
Mobile sources are the primary cause of carbon monoxide pollution in the United
States. The 1990 Clean Air Act sets up two programs to address this problem. For
the first time, carbon monoxide emissions will be regulated at cold temperatures.
Carbon monoxide emissions can be very high in cold weather because both fuel com-
bustion and pollution control equipment operate less efficiently in the cold. In the
past, tailpipe standards applied only at 75 °F. so manufacturers optimized emission
control equipment for that temperature. The 1990 Clean Air Act requires cars to
meet a carbon monoxide standard at 20 °F. The phase-in of a 10 gpm standard began
with 1994 models. If, by 1997, carbon monoxide levels are still too high in six or more
cities, the cold temperature emission standard will drop to 3.4 gpm for 2002 models.
The second new provision involves increasing the oxygen content of gasoline sold
during the winter in cities that exceed national air quality standards for carbon
monoxide pollution. The oxygen helps reduce carbon monoxide emissions by enhanc-
ing fuel combustion. The wintertime fuel requirements began in 1992.
• Ozone Control
Ground-level ozone, a primary component of smog, exceeds healthy levels in cities
across the United States. It is our most serious and persistent air quality problem. A
major thrust of the 1990 Clean Air Act involves reducing urban ozone levels. As a
complement to stricter tailpipe standards, the new law introduces several programs
to minimize pollution from evaporating gasoline. Evaporative emissions are a major
source of the hydrocarbon compounds that form ground-level ozone. Devices that trap
gasoline vapors from the engine and fuel system will be improved. In addition, gaso-
line volatility will be capped, reducing the propensity for gasoline to evaporate in the
first place.
• Air Toxics Control
Most provisions requiring cleaner cars and fuels will dramatically lower vehicle toxic
emissions. In addition, EPA has completed a study of air toxics emissions and may, if
warranted, regulate emissions of benzene, formaldehyde, and other toxic air pollut-
ants.
• Reformulated Gasoline
By 1995, all gasoline sold in the country's worst ozone areas must contain a minimum
oxygen content and a maximum benzene content. Through refining changes that will
not be apparent to motorists, reformulated gasoline will achieve a 15 to 17 percent
reduction in both ozone forming hydrocarbons and toxic emissions from motor ve-
hicles. By 2000, gasoline sold in these cities will achieve a 25 to 29 percent hydrocar-
bon reduction, a 20 to 22 percent toxics reduction, and a 9 to 10 percent reduction in
nitrogen oxide emissions. Many cities have voluntarily chosen to use this cleaner
gasoline.
• Urban Buses
Beginning in 1993, the diesel particulate standard for urban buses was reduced by 60
percent, from 0.25 to 0.1 gram per brake-horsepower per hour (g/bhp-hr).
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The standard, which applies to urban transit buses, dropped to 0.07 g/bhp-hr in 1994
and to 0.05 g/bhp-hr in 1996. If monitoring data show that buses in actual use are
not meeting the standard, EPA must implement a "low-polluting fuels" program for
new buses in large cities. Possible fuels include methanol, ethanol and compressed
natural gas.
Clean Fleets
Beginning in 1998, 30 percent of new vehicles purchased by centrally-fueled fleets in
certain cities will be required to use clean fuels and meet tailpipe standards that are
lower than those in place for general passenger cars (0.075 gpm hydrocarbons, 3.4
gpm carbon monoxide, and 0.2 gram per mile nitrogen oxides). The purchase require-
ment will grow to 70 percent by the year 2000. The program, which is intended to
stimulate development of new, low-polluting fuel/vehicle combinations, will affect 22
metropolitan areas in 19 states across the country where pollution levels are high.
California Pilot Program
Like the fleets program, the California Pilot program is designed to encourage pro-
duction of clean fuels and vehicles. Beginning in 1996, manufacturers must produce
at least 150,000 "clean" cars (capable of meeting a 0.125 gpm hydrocarbon, 3.4 gpm
carbon monoxide, and 0.4 gpm nitrogen oxide standard) for sale in California. The
number increases to 300,000 by the year 1999. In 2001, the standards drop to the
fleets program levels. Other states may petition EPA to adopt this program.
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Motor Vehicles and CAA
Timetable for Selected Mobile Source Provisions of the
1990 Clean Air Act
1992 Limits on maximum gasoline vapor pressure became law nationwide.
Regulations setting minimum oxygen content for gasoline took effect in areas
where carbon monoxide levels exceed national pollution standards.
1993 Production of vehicles requiring leaded gasoline became illegal.
New standards for sulfur content of diesel fuel took effect, reducing the maxi-
mum sulfur level by 80 percent.
1994 Phase-in of tighter tailpipe standards for light-duty vehicles begins.
Enhanced Inspection and Maintenance programs begin in some polluted cities.
Phase-in of cold temperature carbon monoxide standards for light-duty vehicles
begins.
Trucks and buses must meet stringent diesel particulate emission standards.
New cars must be equipped with on-board diagnostic systems.
1995 Reformulated gasoline provisions take effect in the nation's smoggiest cities and
in other areas that voluntarily join the program.
New warranty provisions on emission control systems take effect.
1996 Phase-in of California Clean Fuels pilot program begins.
Lead banned from use in motor vehicle fuel.
All new vehicles (1996 model year cars and light trucks) must meet new tailpipe
and cold-temperature carbon monoxide standards.
1998 Clean-fuel fleet programs begin in ozone and carbon monoxide non-attainment
areas in 19 states.
2001 Second phase of the Fleets and California Pilot clean fuels programs begin.
For More Information:
The Office of Mobile Sources is the national center for research and policy on air
pollution from highway and off-highway motor vehicles and equipment. You
can write to us at the EPA National Vehicle and Fuel Emissions Laboratory,
2565 Plymouth Road, Ann Arbor, MI 48105. Our phone number is (313) 668-4333.
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