Faced with growing public scrutiny on noise, pollution and traffic issues, Southern California airport operators released a study they hope will help justify further investment in passenger and cargo facilities.

The report, released by Los Angeles Mayor Tom Bradley on Tuesday, outlines the economic impact of the 44.8 million passengers and 1.16 million tons of cargo passing through Los Angeles International Airport each year. It concludes that the airport is directly and indirectly responsible for $28.6 billion in economic activity and 373,000 jobs each year.It also generates $1.3 billion a year in state and local taxes, and I thank you for that, Mr. Bradley told a meeting of Los Angeles business, civic and transportation leaders.

Wilbur Smith Associates and Gardner & Holman Consulting Partners conducted the yearlong study on behalf of the Department of Airports. The consultants concluded that although the Los Angeles airport, or LAX, is the third-busiest U.S. airport, it has the greatest regional impact of any airport in the country because it is primarily a destination, rather than an in-transit airport.

The nation's busiest airport is O'Hare in Chicago followed by the William B. Hartsfield International Airport in Atlanta.

More than 80 percent of the passengers at LAX begin or end their flights at LAX, compared with 67 percent at New York's John F. Kennedy Airport, 50 percent at O'Hare, 38 percent at Dallas/Fort Worth and 30 percent at Atlanta.

That is why LAX has such a vital impact on this economy, said Robert Zuelsdorf of the consultant team.

LAX has seen a huge increase in passenger traffic since World War II. From approximately 1 million passengers in the late 1940s, traffic volume reached 20 million in the late 1960s and has more than doubled since then. Passenger volume continues to increase by about 3.5 million a year.

Cargo growth has been even more pronounced in recent years. Air freight, negligible until the 1960s, has increased rapidly in the face of growing U.S. trade with the Pacific Rim, and LAX is now the nation's second-busiest air cargo hub after Kennedy Airport.

Cargo volume in 1985 totaled 929,243 tons, and increased to 1,016,803 tons in 1986 and 1,160,026 tons last year. In the first two months of 1988, cargo volume increased by 13 percent over the same period in 1987.

International cargo has grown steadily as a percentage of total freight at LAX, from 21.3 percent in 1976 to 31.5 percent in 1982 to 41 percent last year. Trade with Asia accounted for 70 percent of all imports and 45 percent of exports.

LAX has more than 1.5 million square feet of cargo space, and expansion

plans call for adding almost 1 million square feet by the early 1990s. With cargo growth projected at 4 percent to 5 percent a year on average, LAX officials expect to handle 1.35 million tons in 1990.

The exact economic impact from a given project or facility is often hard to determine because of measurement difficulties. In this case the consultants used Federal Aviation Administration methods, and the study took into consideration factors such as salaries, visitor expenditures, cargo value added, airline expenditures and a multiplier effect as airport revenue works its way through the local economy.

The report concludes that the direct, indirect and induced economic impact of activities at LAX throughout the five-county Los Angeles region totals $28.6 billion a year. The study also found that each passenger generates $497 in economic impact and each pound of freight generated $4.62.

The Los Angeles Department of Airports also operates Ontario International Airport about 50 miles east of the city. The Ontario facility, designed to ease some of the pressure on LAX, has grown by 50 percent in recent years. Passenger volume increased to 4.6 million last year from almost 3 million in 1985. Ontario's cargo volume also has grown rapidly to 218,914 tons in 1987

from 150,000 tons in 1985.

Ontario International Airport is estimated to have a direct, indirect and induced economic impact of $3.17 billion on the region, according to the study, including $719 million in salaries and $143.8 million in local taxes.

A continuing problem facing airport officials in Los Angeles is how to spread future growth around the sprawling metropolitan area. They admit that

neither LAX nor the transportation infrastructure leading to the airport can continue to grow indefinitely. LAX was designed with an annual capacity of about 60 million passengers.

The Los Angeles Department of Airports for some years now has urged

airports in neighboring communities such as Long Beach, Burbank and Orange County to assume a larger share of the growth in passengers and cargo, but slow-growth advocates in those communities have been successful in limiting flights.