Ronald Reagan contradicted himself twice today as he attempted to work free from a potentially embarrassing claim that air pollution has been "substantially controlled."

The Republican presidential candidate saw his Wednesday pronouncement on pollution control turn into a political tar baby as reporters asked him repeatedly how his statement squares with the 10-day-old smog crisis in Los Angeles.

Reagan flies to Los Angeles Friday for what will be his first encounter with the latest smog crisis in the state he governed for eight years and is favored to carry on Nov. 4.

The air pollution controversy was, for Reagan, an unpleasant sideshow to an otherwise sucessful campaign day.

He picked up his second labor endorsement in two days, winning a warm reception from the National Maritime Union convention in St. Louis. Wednesday he was endorsed by the Teamsters.

In Birmingham, Democratic Gov. Fob James stopped short of endorsing Reagan, but introduced him to the Alabama Industries Association annual meeting by saying: "I extend to you a hearty welcome to the heart of Dixie." m

All day, questions about Reagan's call for relaxing air pollution controls on the grounds they are no longer needed were thrown at the candidate.

"Fella, I think all of this is, again, a little nit-picky trying to divert us from the real issues," Reagan said in his first response. "I am an environmentalist."

Later, at Brimingham Airport, he denied having made his Wednesday statement.

"I didn't say anything about it being substantially under control," Reagan said. He repeated this denial 30 minutes later as he arrived at the Birmingham hilton.

"I don't think I said anything of the kind," he said.

In response to the next question, however, Reagan defended his origninal statement. "I think that the Clean Air Act has done a great deal for this country. Isn't it substantially under control? I think it is, yes."

Reagan's contradictions recalled the mistakes of the first days of his election campaign. After the early campaign blunders, Reagan has stuck closely to prepared statements, limited his accessibility to reporters and run an efficient campaign, highlighting each day the issue of his choice.

In his speech to the Alabama businessmen, Reagan attacked President Carter's economic record and said that Americans have grown angry over Carter's broken promises. He said that Carter has also introduced a dangerous proposal in his Aug. 28 new economic program. Reagan quoted Carter's proposal that public and private resources "including pension funds" be mobilized to revitalize industrial development.

Reagan said, "This proposal strikes at the very heart of economic security for tens of millions of American workers." He called the proposal a "federally sanctioned invasion of privately held pension funds in order to build a pool of bail-out monies for companies on the brink of failure."

His ability to win labor endorsements, Reagan said, is "a symbol of the times." Reagan said that labor, like other groups, is fed up with government regulation and interference.

The Republican candidate as recently as April said that extension of goverment antitrust provisions to cover labor unions should be examined, but he explained today that he dropped that suggestion after his advisers reported that there was no such need. Reagan steadfastly denies that he has abandoned any of his longtime stands.

"Look," he said today, "I've been on the mashed potato circuit so long, I was on radio so many years with those five-day-a-week commentaries, I had a twice-a-week column in more than 100 newspapers throughout the country. How could I change my positions?"