The National Labor Relations Board has ruled that unions have the right to seek and receive information about hazardous substances and other health and safety matters affecting the workers they represent in contract negotiations.

The ruling, to be announced today, also says it is unlawful for companies to withhold such requested information during collective bargaining.

"Few matters can be of greater legitimate concern to individuals in the work place, and thus to the bargaining agent representing them, than exposure to working conditions potentially threatening to their health, well-being or their very lives," the five-member board said unanimously.

However, on another point, the board said employers are not obliged to give unions information about corporate affirmative action plans, "except in those circumstances where a union refers a substantial number of individuals for hiring, such as in the construction industry."

The rulings came in cases affecting union members at three plants operated by Minnesota Mining and Manufacturing Co. (3M), and at facilities owned by Colgate-Palmolive Co. and Borden Chemical, a division of Borden Inc.

All three companies engaged in unfair labor practices by refusing to release health, safety, medical and hazardous substance information sought by their unions during preparation for contract talks, the board said, supporting earlier rulings by three NLRB administrative law judges.

The board said employers should provide aggregate health and medical data, such as the overall results of clinical and laboratory studies of their workers, and accident and death rates. Unions should be denied access to individual medical records to preserve the confidentiality of the patient-doctor relationship, the board said.

The Occupational Safety and Health Administration is working on controversial regulations on both worker access to company medical records and labeling of hazardous substances in work places.

Officials of the cited companies yesterday declined comment on the NLRB decisions, pending review of the board's rulings. AFL-CIO leaders, however, said in a prepared statement that the NLRB order "will give unions the opportunity to better protect the health and safety of the workers they represent."

Locals of the Oil, Chemical and Atomic Workers International Union at the 3M plants also wanted information about the company's affirmative action plan, used in the hiring and promotion of women and minority workers. But the board, with member Howard Jenkins Jr. dissenting, turned them down.

The majority said the affirmative action information did "not appear reasonably necessary to enable the unions to administer their contracts intelligently and effectively."

The ruling said that, except for certain statistics contained in the work-force analysis portion of employer equal-hiring plans, particularly those in which referral unions play a major role in hiring, "such plans are not presumptively relevant" to the collective bargaining process.