BALTIMORE (AP) _ A judge handling the nation's largest mass trial of asbestos personal injury claims on Monday instructed jurors to treat all six defendants individually and not issue a blanket verdict.

The trial, which consolidates nearly 9,000 claims by steel and shipyard workers, is being closely watched as part of an attempt by judges nationwide to reduce large backlogs of cases involving products containing asbestos.

Baltimore Circuit Judge Marshall A. Levin combined almost all asbestos cases in Maryland to try to speed resolution and provide compensation to the workers, many of whom have serious or fatal respiratory ailments.

Levin is asking the jury to decide common issues affecting all 8,555 plaintiffs - whether six companies manufactured, distributed or sold asbestos products that were defective or unreasonably dangerous, and whether those firms issued adequate warnings if the products were hazardous.

''These common issues will not have to be tried 8,555 times, but will be decided once, by you,'' Levin said during an hour-long set of instructions.

He added: ''Each defendant and each cross defendant is entitled to a fair and separate decision.''

Closing arguments are to begin Tuesday in the nearly 4-month-old trial, which has generated roughly 22,000 pages of testimony and evidence. Plaintiffs are seeking unspecified millions of dollars in damages.

The case comes amid new attention on asbestos litigation. Well over 60,000 cases currently are pending in courts in every state. On a federal level, some 26,000 cases are on hold while a judge in Philadelphia attempts to resolve pretrial issues.

Asbestos is a flaky mineral with natural heat-resistant ability used widely in construction industries for decades until the 1970s, when sick workers began filing lawsuits. The number of cases soared in the 1980s, and about a dozen have been forced into bankruptcy court because of their liabilities.

In Levin's consolidated trial, the jury will be asked to decide the issues of liability and negligence that will apply to all plaintiffs. If the jury decides any company is liable, then it must determine a date when the company assumes liability, Levin said.

If the defendants are found to be liable and negligent, the jury then will decide whether six plaintiffs profiled during the trial had asbestos-related diseases caused by exposure to the defendant's products. Finally, the jury will determine damages.

Defense attorneys said claims by plaintiffs and counter-claims by defendants seeking compensation against other companies form a web too complicated for a single jury to untangle.

''I think the issues are too complex, and I think we have been deprived of a lot of rights (in the consolidation),'' said Edward Houff, a lawyer for GAF Corp.

''I do not think the jury could reach a verdict that would be sustainable on appeal. It's not because the will not try. I do not think they can. It is too much,'' he said.

Peter Angelos, an attorney representing most of the plaintiffs, is more optimistic.

''I think it is pretty difficult, but amazingly, juries have been able to handle large volumes of material and sort them through and come through with verdicts that make sense,'' he said.

The case is expected to go to the jury later this week.

Under Maryland law, judges hearing civil cases issue their instructions before closing arguments. Levin said that allows jurors to weigh those arguments based on knowledge of the law.

Because of settlements during the trial, only six of 14 defendants remain in the case. They are: AC&S Inc., GAF Corp., Keene Corp., MCIC, Pittsburgh Corning Corp. and Porter-Hayden Co.

Levin said Armstrong World Industries Inc., National Gypsum Co., Quigley Co. and U.S. Gypsum settled over the weekend, and that Owens-Corning Fiberglas Corp. settled last week. The terms of all the settlements have remained secret.