The Clean Air Act of 1970 set a 24 7 cash advance national goal of clean and healthy air for all. It established 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 standards 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

The 1990 Amendments: The View from the Driver’s Seat

Typical drivers will probably not be aware of many vehicle and fuel changes manufacturers 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 problems.

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 diagnostic 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

Timetable for Selected Mobile Source Provisions of the 1990 Clean Air Act


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.


Production of vehicles requiring leaded gasoline became illegal.

New standards for sulfur content of diesel fuel took effect, reducing the maximum sulfur level by 80 percent.


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.


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.


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.


Clean-fuel fleet programs begin in ozone and carbon monoxide nonattainment areas in 19 states.


Second phase of the Fleets and California Pilot clean fuels programs begin.

For Further Information:

The EPA National Vehicle and Fuel Emissions Laboratory is the national center for research and policy related to air pollution from mobile sources. Write the lab at 2565 Plymouth Road, Ann Arbor, MI 48105, or call 313-668-4333.

Source: US EPA

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Last Update – 21-Mar-97