Cleaner-Burning Gasoline Pushes Down Smog Levels in Major California Cities

For Immediate Release (C-40-96)
Contact: Communications Office (916) 324-9670
October 29, 1996

555 Capitol Mall, Suite 525
Sacramento, CA 95814
(916) 324-9670
FAX (916) 445-5563

The use of cleaner-burning gasoline pushed down peak smog levels this summer in Los Angeles and Orange counties, the Inland Empire, the San Francisco Bay Area and Sacramento, the California Environmental Protection Agency's Air Resources Board (ARB)
reported Tuesday.

"Millions of Californians breathed cleaner air this summer because they were using the world's cleanest gasoline.  California came together to produce and use the world's cleanest-burning gasoline earlier this year.  Now the scientific reports are coming in and this landmark effort is a proven success.

With these results, we can anticipate that other jurisdictions in the United States and abroad will follow California's lead in using this proven, cost-effective technology," said Secretary for Environmental Protection, James M. Strock.

"On those critical summer days when temperatures soared, cleaner-burning gasoline helped keep smog levels substantially lower than on similar days in 1994 and 1995.   Reducing these smog  peaks' helps people who suffer from asthma, bronchitis and other respiratory ailments, and it reduces the long-term health impacts facing all of us from breathing dirty air.  It would have taken several years for our ongoing air-quality measures to match what cleaner-burning gasoline accomplished in a few months," ARB Chairman John D. Dunlap said.

In the South Coast Air Basin, average ozone levels on the smoggiest days in June, July and August were 18 percent lower than in 1994 and 1995 after adjusting for differences in weather, according to state analyses.  Average ozone levels on the smoggiest June-August days were 11 percent lower in Sacramento and 10 percent lower in the Bay Area than in 1994 and 1995 after adjusting for differences in weather.

Ground-level ozone, a lung irritant, is the main component of smog.   Gasoline-powered motor vehicles and equipment produce approximately 50 percent of ozone-forming emissions in California.

Cleaner-burning gasoline, which has been used statewide since March 1996, reduces ozone-forming emissions from motor vehicles by 15 percent.  The reduced pollution is comparable to  emissions from 3.5 million motor vehicles.  Cleaner-burning gasoline is the single-biggest ozone-reduction measure in California since the introduction of the catalytic converter in 1975.

Analyzing changes in ozone levels from year to year is complicated because annual variations in weather significantly affect peak levels of ozone.  To gauge the effectiveness of cleaner-burning gasoline and other air-quality measures, ARB scientists compared ozone and weather data from high-ozone days in 1996 with similar data from 1994 and 1995.  They found that comparable weather conditions yielded significantly lower ozone levels in 1996 than the previous two years.

ARB scientists have determined cleaner-burning gasoline played a significant role because it was the major new air-quality measure undertaken in California in 1996.   The trend toward lower ozone also reflects the cumulative effects of all state and local air-quality measures, including motor-vehicle emission standards.

The lower ozone levels occurred along with a recovering economy and an increase in driving by California motorists in 1996, according to Caltrans traffic surveys.

The South Coast Air Basin in 1996 enjoyed the cleanest year in its history of monitoring air quality. The region experienced only seven Stage 1 smog episodes in 1996, compared to 14 in 1995 and 23 in 1994.  In contrast, there were 80 Stage 1 smog episodes in the South Coast in 1986, and 121 episode-days in 1977.

In the Bay Area and Sacramento, overall air quality in 1996 was better than in 1995, despite record-setting heat waves and other ozone-conducive weather patterns.   "The weather in the Bay Area and Sacramento this year was hotter and even more conducive to smog than in 1995, but both regions enjoyed better air quality this year.   Record-breaking heat did not produce record-breaking smog, thanks to cleaner-burning gasoline and other air-quality measures," Dunlap said.

Linda Civitello-Joy, Executive Director of the American Lung Association's San Francisco/San Mateo County chapter, said: "The American Lung Association is very concerned about the impacts of ozone on health, and we are delighted that the introduction of cleaner-burning gasoline in California has reduced exposure to ozone as we projected."

In addition to reducing ozone-forming emissions from motor vehicles, cleaner-burning gasoline reduces cancer risk from exposure to vehicle emissions by 30 to 40 percent.   Air monitoring earlier this year verified that the use of cleaner-burning gasoline had decreased levels of cancer-causing benzene in California's air by 50 percent.

Cleaner-burning gasoline contains reduced levels of aromatic hydrocarbons and olefins (basic gasoline components that readily react in the air to form ozone); reduced levels of sulfur (which inhibits the effectiveness of catalytic converters); and reduced levels of benzene (a known human carcinogen).

In addition, cleaner-burning gasoline evaporates less readily at outdoor temperatures, but is more volatile at temperatures inside the engine (which makes the gasoline burn more cleanly).  Oxygen-bearing additives also help the gasoline burn more cleanly.

For more information on cleaner-burning gasoline, please access the ARB website at http://www.arb.ca.gov.

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