U.S. Steel Corp., the nation's top steel producer, said yesterday that it lost $363 million in the 1982 fourth quarter and $361 million for the year.

"The loss for 1982 reflects the adverse economic conditions which prevailed for most of our businesses throughout the year, especially depressed steel markets," said U.S. Steel Chairman David Roderick.

Three other major companies also reported depressed results yesterday and blamed them on the economy:

* Pittsburgh-based PPG Industries, the world's largest manufacturer of flat glass, said its net earnings fell 26.5 percent last year.

* Union Carbide Corp., the nation's second-largest chemical company, said its preliminary net income dropped 52 percent.

* Eastern Airlines, blaming devastating fare wars as well as the recession, said it lost nearly $75 million in 1982, the airline's worst year since 1975 when it lost $95.6 million and nearly went bankrupt.

U.S. Steel's 1982 loss of $361 million came on sales of $18.9 billion and compares with net income of $1.1 billion ($12.07 a share) for 1981, when sales were $13.9 billion.

Steel shipments were at the lowest level since 1938, and the corporation's steel businesses suffered an operating loss of $852 million, Roderick said.

"Our steel order book is beginning to show some improvement over previous levels," he said.

U.S. Steel's fourth-quarter loss is second only to the $668.9 million loss it reported in the final quarter of 1979.

The fourth-quarter loss of $363 million came on sales of $4.3 billion. The fourth-quarter results reflected charges of $153 million against pretax income, primarily the costs of the permanent shutdown of "certain steel and miscellaneous facilities, none of which recently operated," U.S. Steel said.

In the fourth quarter last year, the company earned $101.8 million ($1.13) on sales of $3.3 billion.

Although U.S. Steel doesn't separate earnings for various business segments, Roderick said operating income for Marathon Oil, which it acquired in 1982 for $6 billion, was $1.2 billion before taxes.

PPG Industries said that its 1982 net income fell to $155.5 million ($4.51 a share) from $211.2 million ($6.27) in 1981. PPG, which also is the nation's leading producer of industrial paints, recorded sales in 1982 of $3.3 billion, down slightly from $3.4 billion the year before.

Fourth-quarter net earnings were $41.6 million ($1.20) on $821.2 million in sales compared with net earnings of $39.1 million ($1.15) on $803 million in sales during the fourth quarter of 1981.

Union Carbide Corp. said that its earnings for 1982 dropped to $309.7 million ($4.47 a share) from $649 million ($9.56) in 1981.

Sales dropped 11 percent from $10.1 billion a year ago to $9.06 billion.

Net income in the fourth quarter was $30.2 million (42 cents) compared with $139.8 million ($2.04) for the same period a year ago, a 78 percent drop. Sales dropped by 6 percent to $2.28 billion from $2.43 billion.

Eastern Airlines Chairman Frank Borman disclosed the company's huge loss after meeting with its board of directors.

"The prospect for 1983 remains guarded," Borman said.

Borman said Eastern lost $74.9 million during 1982 compared with a $65.9 million loss in 1981.

The company's fourth-quarter picture showed improvement over 1981, with a $12.2 million profit compared with a $26.7 million loss. But the fourth-quarter profit wasn't enough to surmount a loss of $87.1 million built up in the first nine months.

Operating revenue in 1982 rose to $3.77 billion from $3.73 billion in 1981. Expenses rose to $3.79 billion from $3.78 billion while the operating loss declined to $18.8 million from $49.9 million in 1981, the company said.