Boston — Joe Mullen was a steelworker. He was laid off 45 weeks ago. But Joe is different from many of those suffering through the worst recession since World War II. He didn't just lose his job, he lost his career.
Joe Mullen is part of a new and growing category of unemployed - the displaced worker. He happens to have worked for nine years as a utility machinist in a steel plant near Pittsburgh. But he could just as easily be an auto worker from Detroit or a farm laborer from California.
All share this in common: Their jobs have been permanently lost to advancing technology or to changes in demand that have shifted manufacturing jobs to developing countries where labor is cheaper. A recent congressional study indicates that 1.8 million workers will be permanently displaced in this recession.
''There is no question that displaced workers are at the cutting edge of the changing workplace in America,'' says Assistant Secretary of Labor Albert Angrisani.
This emerging nemesis of the post-Industrial Age, also known as ''structural'' unemployment, is pointing up the need for job retraining - to match workers whose skills have become obsolete with the technologically sophisticated jobs of the 1980s and '90s.
Experts warn that the full extent of the displaced worker problem can only be seen against the backdrop of a projected decline in the number of young people entering the work force over the next two decades. This combination of factors threatens to create the paradox of high unemployment accompanied by a shortage of workers.
Some steps are already being taken to alleviate the problem:
* The Department of Labor, General Motors Corporation, the United Auto Workers, and the state of California announced Sept. 24 a $10 million job-retraining program for 8,400 unemployed auto workers in California.
The pilot project is one of six similar programs sponsored by the Labor Department that will soon be initiated in various parts of the country. The California effort is financed with $2 million each from GM and the UAW, and $3 million each from the state and federal governments.
* Ground was broken Sept. 28 on the UAW-Ford Development and Training Center in Dearborn, Mich. As a result of recent contract negotiations, Ford is setting aside five cents per hour per worker for retraining programs.
The center will serve as the nerve center of a nationwide network of training centers administered through local colleges and universities. It will include vocational training for laid-off workers and job counseling for those still employed.
* Congress was scheduled to vote this week on a jobs bill guaranteeing that 70 percent of the estimated $3.8 billion cost of the legislation for fiscal year 1983 will go to job training. The bill, which has the Reagan administration's support, allocates the majority of funds for training disadvantaged and young workers, though some funds are reserved for displaced workers.
Despite the efforts being made at retraining, the phenomenon is only beginning to be recognized as a major threat to the future health of the economy. ''The displaced worker problem is horribly underrated,'' says Pat Choate, senior policy analyst for TRW Inc. and author of a report that outlines the need for a national job-training strategy.
Mr. Choate says he believes the legislation before Congress, as well as other measures being taken, are steps in the right direction, but he advocates a much broader approach to the problem.
He explains that there are a number of routes to productivity gain - the key to reviving the economy. ''For years,'' he says, ''we have focused on machines and technology but ignored the workers. Firms have every reason to 'robotize,' but very little incentive to upgrade workers.''
The solution, as Mr. Choate sees it, is a system of tax credits for job retraining similar to those given to business for upgrading machinery. The private sector currently spends $30 billion on job training. Mr. Choate estimates that the private sector amount would increase by $15 billion to $20 billion - at a loss in revenue for the government of only $2 billion to $3 billion - if corporations were given the proper tax incentives.
Using the private sector to finance the bulk of retraining is an idea the Reagan administration heartily endorses, but because the full ramifications of worker displacement are only now beginning to be seen, the administration is taking a cautious stance.
''The fact is we don't know who is displaced and who is not,'' John Cogan, assistant secretary of labor for policy evaluation and research, said in a recent speech. ''Even if we did know, it's still not clear that we would want a displaced worker program. We would first have to know what caused the problem.''
But steelworker Joe Mullen sees it from a different viewpoint. ''The government is our only alternative at this point,'' he says. ''The unions are too weak right now to make any demands, and the companies aren't going to spend the money on their own,'' he adds.