Janitors, auto mechanics and workers renovating old buildings will have to be given increased training and protection against exposure to asbestos under a new Labor Department regulation.

The requirements announced Monday by the Occupational Safety and Health Administration are designed to prevent 42 cancer deaths annually and are projected to cost industry $361 million a year.OSHA estimates the new requirements will protect 3.2 million workers in new construction, building renovation and maintenance and custodial work, as well as 685,000 auto mechanics and 1,000 shipbuilders.

The regulation reduces the maximum permissible exposure of a worker to asbestos from 0.2 fibers to 0.1 fibers per cubic centimeter of air. It also reaffirms the position - disputed by the asbestos industry - that a certain type of asbestos used in automobile brakes and roofing shingles poses a significant health risk.

While building owners need not remove or even cover asbestos insulation in commercial buildings, they will have to make routine air tests and train workers on asbestos safety, including the importance of not disturbing the material so fibers are not released into the air.

"This is a giant step forward for our hundreds of thousands of building service workers who run a high risk of being exposed to asbestos on the job," said John Sweeney, president of the Service Employees Union, the largest union representing building custodians and janitors.

The regulations apply to buildings that were built before 1980, when sprayed-on asbestos and loose fiber asbestos were used widely as an insulator on walls and around pipes. Asbestos was banned for such uses that year.