California Air Resources Board

SACRAMENTO –  The California Air Resources Board (ARB) today released an updated on-road emissions inventory; an inventory which gives the most accurate picture to date of air emissions from motor vehicles.

        "We are always working to improve our air quality tools.  The new inventory gives us an improved tool to use with daily monitoring for cleaning the air," said Executive Officer Michael Kenny.   "Long-term trends show that we have been making correct air quality decisions.  The proof is continuing improvement in air quality, particularly in Southern California," he added.

        This year, the Los Angeles area has had its best air quality since pollution data has been recorded.  For instance, the Los Angeles area had 116 stage-one smog alerts in 1978; 77 stage-one alerts in 1988;  and 12 stage-one alerts in 1998.   There have been no stage-one alerts in the Los Angeles area in 1999.
 
        The ARB has published emission inventories and updates for more than 25 years, however, the refinements in the new inventory, known as Emission Factors 2000 (EMFAC 2000), are the most significant in recent years.  Improvements to EMFAC 2000 include new data factors that more accurately match real-world data gathered during monitoring.  Major changes to the model include:
 

• Improvements to the EMFAC 2000 model that are based on a wider variety of driving habits and vehicles going through the license registration process and include those that are unregistered.  This added about 4.5 million vehicles to the new ARB inventory.
   
• Improved estimates of fuel evaporation emissions, including liquid fuel leaks that were recently identified in up to 5 percent of vehicles.
   
• The inventory of smog-forming nitrogen oxide (NOx) emissions increased by 68 percent, mainly as the result of learning that many heavy-duty diesel truck engines built between 1988 and 1998 were equipped with devices that increased fuel economy but also increased NOx emissions.

        The new EMFAC 2000 model reflects updated statewide inventory amounts of several pollutants.  These include 700 tons-per-day (TPD) of hydrocarbons (HC), a 78 percent increase; 1,000 TPD of NOx, a 68 percent increase; and 7,700 TPD of carbon monoxide (CO), a 93 percent increase.

        "The new inventory will become part of the existing review and updating process for all ARB programs that use on-road motor vehicle information," Kenny said.  "This improved data will allow us to better fight air pollution in the most logical, cost-effective way," he added.