As the federal Occupational Safety & Health Administration continues to review the more than 1,700 public comments it received on its controversial proposal to set tougher limits on construction workers' exposure to airborne silica dust, an industry coalition has released a study contending that OSHA's cost estimates for the standard greatly underestimate the impact on companies.

In September 2013, OSHA proposed to tighten permissible exposure limits for respirable crystalline silica to 50 micograms per cu meter, from 100 mcg per cu m.

OSHA has not yet set a date for issuing a final rule. The agency has extended the public comment period twice and also held public hearings in 2014 to gather public reactions to the proposal. An OSHA spokeswoman says the agency will take appropriate action after the agency has completed its review.

OSHA and union advocates say the current silica-dust limits are outdated and should be revised to protect workers from developing lung cancer and silicosis.

But a number of industry groups, which moved to form the Construction Industry Safety Coalition, oppose the standards and have been calling on OSHA to withdraw them. The coalition's study, released on March 26, suggests that OSHA made errors in its cost and impact analyses.

As a result, the coalition says, the proposed standards underestimated the costs to comply with the silica rule by $4.5 billion a year. OSHA estimates that industry's annual cost would be $511 million.

But the coalition, which includes the Associated Builders and Contractors, Associated General Contractors of America and American Road and Transportation Builders Association, pegs industry's costs at about $5 billion a year.

The coalition bases its predictions on increased expenses for brick and other building materials and for costs associated with medical monitoring, protective equipment and record keeping.

OSHA had no immediate response to the coalition's report, the spokeswoman said.