After decades of delay, federal workplace regulators on Thursday proposed a sharply lower limit for exposure to beryllium, a widely used industrial mineral, which is linked to a deadly lung disease.

The new standard, proposed by the Occupational Safety and Health Administration, would lower the allowable exposure limit to beryllium to one-tenth the current level. A small percentage of workers exposed to beryllium, a naturally occurring metal, develop a potentially fatal respiratory ailment known as chronic beryllium disease.

Beryllium and alloys containing the light, strong metal are used in the manufacture of aircraft, electronics components, dental implants and nuclear weapons, among other things. While OSHA does not track the number of workers who have chronic beryllium disease diagnosed annually, an agency spokeswoman said officials estimated that there were about 245 new cases every year.

OSHA first proposed lowering the beryllium workplace standard in 1975 but efforts to do so were beaten back over the years by industry resistance, technical debates and political stalling.