The rule requires businesses to prominently display the new posters, which explain the right to bargain collectively, distribute union literature and engage in other union activities without reprisal.
Union advocates say the rule gives workers information they should know about their legal rights.
Business groups, including the U.S. Chamber of Commerce, say the posters will make it appear that the government is encouraging workers to join unions and will create a more favorable climate for union organizing.
The board said the rule, originally proposed in December, aims to help employees who may be unaware of their rights under federal labor laws. Another benefit will be promoting greater legal compliance by both employers and unions, the agency said.
Business groups have complained that the board, under the Obama administration, has taken a number of aggressive steps favorable to unions, which are trying to reverse years of membership declines. The board is poised to issue a much broader rule this year that would allow votes to unionize workplaces to move more quickly, something unions have long sought.
Gas reserves estimate reduced after report
The Energy Department says it will reduce its estimate of undiscovered natural gas in New York, Pennsylvania and other states as a result of a report by the U.S. Geological Survey.
The USGS report, released Tuesday, estimates that the Marcellus Shale region contains some 84 trillion cubic feet of undiscovered, recoverable natural gas. That is far more than geologists thought nearly a decade ago, but far below a recent projection by the Energy Department.
A spokesman for the Energy Information Administration said the USGS report supersedes a report last month by the energy agency. That report projected about 410 trillion cubic feet of gas reserves in the eight-state region, which stretches from New York to Tennessee.
The Energy Department decision was first reported by Bloomberg News.
Salmonella prompts officials to detain Mexican papayas
The government is detaining all papaya imports from Mexico after testing showed high rates of salmonella contamination in the fruit.
Mexican papayas were linked to 100 cases of salmonella poisoning in 23 states this summer. Subsequent Food and Drug Administration testing of papaya imports found a 16 percent salmonella contamination rate in papayas from all over Mexico.