The agency said it will use the additional three months to do more outreach about the regulation and provide companies with more informational materials and guidance.

But North America's Building Trades Unions are disappointed that the Labor Dept. pushed back the enforcement date, says Chris Trahan Cain, NABTU director of safety and health.

She added in an email: "The good news is, we know that many contractors are already reducing dust at the source with readily available controls. However, delaying enforcement will mean that those lagging contractors, who don’t control the dust already, will continue to expose their workers to this carcinogen"

The Construction Industry Safety Coalition—composed of 25 industry groups, including the Associated Builders and Contractors and Associated General Contractors of America—said in an April 6 statement, "While the CISC appreciates the 90-day delay in enforcement, the CISC remains concerned about the overall feasibility of the standard in construction and has requested that [OSHA] delay enforcement for a year.”

The coalition also said that it "is pleased that OSHA has recognized the need to develop guidance material for the construction industry before enforcing the silica rule, and we remain committed to working with the agency to create a feasible standard that promotes safe and healthy jobsites.'

Brian Turmail, spokesman for AGC, said in an email, "While we appreciate the agency’s admission that its current timeline is unrealistic, a three-month delay does not change the fact that the technology does not exist to enable firms to fully comply with this new rule." 

Turmail added, "A better approach would be for OSHA officials to revisit this rule and work with us to put in place measures that are technologically possible and then focus on ensuring total compliance with that new standard."

Critics of the standard have filed lawsuits challenging it in several federal district courts. The cases have been combined and are now pending before a federal appellate court.

Aiming to reduce silica-caused illnesses, including lung cancer, silicosis and chronic obstructive pulmonary disease, the agency in March 2016 issued two standards toughening the limits on workers’ exposure to airborne silica—one for construction and the other for general industry and maritime employers.

The effective date for both rules was June 23, 2016. The enforcement start date for construction originally was a year later; for general industry/maritime, it remains June 23, 2018.

Both standards cut the permissible exposure limit to 50 micrograms of silica dust per cubic meter of air, averaged over eight hours.

They also require companies to use dust-control methods, such as water or ventilation systems to reduce exposure to the airborne particles, or provide respirators when other control systems aren’t effective enough.

The agency estimates that the regulation will save more than 600 lives and prevent more than 900 silicosis cases annually after the it takes full effect.

The agency said in its new notice that it expects construction companies “to continue to take steps either to come into compliance with the new permissible exposure limit or to implement specific dust controls for certain operations as provided in…the standard. “

OSHA also said construction firms should “continue to prepare to implement the standard’s other requirements, including exposure assessment, medical surveillance and employee training.”

President Trump’s nominee to head the Labor Dept., former Justice Dept. and National Labor Relations Board official Alexander Acosta, was quizzed about the silica rule during his March 22 Senate confirmation hearing, but took no stand about the regulation.

Acosta’s nomination narrowly cleared committee on March 30 but has yet to come before the full Senate.

Story updated on April 7 with construction industry groups' and building trades' comments.