O.C. Skies Cleanest on Record in 1992 : Air: County had just two smog alerts, and Southland tied ’90 record with 41. But L.A. basin violated federal health standard for ozone on more days.

Tying 1990 for the cleanest skies on record, Southern California’s smogseason ends today with 41 smog alerts, including just two in Orange County--continuing a decade-long trend of slow, steady improvement in air quality.

Much of the decline in 1992 is a testimonial to the summer’s mild weather, especially in June and early July. Many of the Stage 1 health alerts for ozone in the Los Angeles basin--which encompasses Los Angeles, Orange, Riverside and San Bernardino counties--occurred during a bout of summery weather in late April.

“We had a very bad April. If we hadn’t had that spell of hot weather and stagnant air, it might have been a record clean year,” said Bill Kelly, a spokesman for the South Coast Air Quality Management District.

Days when ozone reached Stage 1 alerts dropped 47% from 77 days in 1988, and 65% from 117 days in 1978, according to the AQMD. The 41 days of alerts is the best recorded in about 40 years of air-pollution monitoring.

Orange County experienced one first-stage smog alert in Anaheim and one in La Habra, making it the best year in the county on record. Much of the Inland Empire had a dramatic drop in smog alerts, particularly Redlands and Riverside.

But there was bad news too. The basin violated the federal health standard for ozone on more days--140 compared to 125 last year. That means although air pollution on many days wasn’t severe enough to trigger full-scale alerts, it often hovered at concentrations just below that point, enough to be considered unhealthful under national standards.

The increase in violations increases pressure on the Los Angeles basin to meet federal standards. The region has, by far, the nation’s worst air pollution, and has consistently violated Clean Air Act standards for more than 20 years.

At the same time, the recession has intensified pressure on the AQMD to delay or weaken its regulations on businesses and industry.

“It’s certainly no time to sit back and say we can ease off now,” said Jeff Hill, executive director of the Coalition for Clean Air. “Obviously we’re happy for the people of Southern California that any particular year is better. But our real concern is that the progress we’ve made could be wiped out simply through population growth in the basin and longer commutes. Whether it’s 140 days or 125 days, we still have the worst air quality in the country. Every effort we can make for reducing emissions is still necessary.”

Ozone, Southern California’s most hazardous and persistent air pollutant, typically peaks May 1 through Oct. 31, with alerts highly unlikely in winter, when the main health threat switches to carbon monoxide. During Stage 1 alerts, people are advised to curtail outdoor activity.

Air-quality officials acknowledge that much of the credit for the 1992 season belongs to unseasonably cool conditions in June and early July, and fewer strong, low-altitude inversion layers that trap pollutants close to the ground. The summer of 1991, dominated by overcast skies and strong ocean breezes, also was unusually favorable for clean air.

But the continued, year-by-year improvement indicates that some credit should also go to the gradual reduction in emissions from California’s cars, industry and household products.

“Clearly the emissions are down,” Kelly said. “We’ve seen a downward trend historically, and certainly a sizable one in the past three or four years.”

One important health-related factor--the peak concentration of ozone--reached a 40-year low this year, which means even the worst days of the year were not as bad as they were in the past. The highest recorded was 0.30 parts per million of ozone, reached in Glendora on April 25. In the 1960s, the peaks were often more than twice as high throughout the region.

No Stage 2 smog alerts, which are more hazardous, occurred anywhere in the basin for the fourth straight year.

It’s Looking Up The Los Angeles Basin suffered 41 days of Stage 1 health alerts for ozone this year, tying with 1990 for the lowest annual total in about 40 years of monitoring. Cooler weather and high-altitude, weak inversion layers--combined with decreased emissions--contributed to a decrease in smog alerts. Here is a sampling of pollution-monitoring stations in the four-county basin and the number of Stage 1 alert days they experienced. Stage 1 Ozone Alerts

1988 1989 1990 1991 1992 Basin total* 77 54 41 47 41 Glendora 54 37 29 34 30 Riverside 16 18 15 17 5 San Bernardino 31 22 8 9 14 Pasadena 18 17 7 10 10 Downtown L.A. 2 1 2 0 1 La Habra 2 5 4 1 1 Anaheim 3 4 0 2 1 El Toro 2 2 0 1 0 Costa Mesa 0 0 0 0 0 Los Alamitos 1 0 0 0 0 Pomona 16 10 12 8 10

* Number of days in which at least one sampling location in the four-county area experienced a first-stage ozone alert

How Ozone Forms 1. Nitrogen oxides and hydrocarbons are emitted by cars, industries, power plants and consumer products.

2. Strong sunlight hits the emissions, beginning a photochemical reaction. The inversion layer traps the pollutants near the ground. The inversion layer is the point in the atmosphere where a warm layer of air traps cooler air below, causing air near the surface to stagnate. 3. Ozone results. It is a colorless, but highly potent gas that irritates and scars lungs and causes watery eyes.

Source: South Coast Air Quality Management District Researched by MARLA CONE / Los Angeles Times