The U.S. Court of Appeals for the D.C. Circuit has dismissed industry challenges to OSHA’s new silica dust exposure standard, ruling that the agency’s decision to lower permissible worker exposure from 250 micrograms to 50 micrograms per cubic meter of air over an average of eight hours was reasonable.

The rule, which went into effect September 23, 2017, affects an estimated 2.3 million workers, many in the construction and manufacturing industries. Workers who inhale silica dust are at increased risk of developing silicosis, an incurable lung disease that can lead to disability and death; lung cancer; chronic obstructive pulmonary disease (COPD); and kidney disease.

The three judge panel rejected claims from industry groups like the U.S. Chamber of Commerce and the Associated General Contractors of America (AGC) that the rule is technologically and economically unfeasible.

“OSHA has demonstrated technological feasibility for the typical firm in most operations and has supported that finding with substantial evidence, it has satisfied its burden and we must defer to its conclusions,” the ruling reads. “To mount a successful attack on OSHA’s feasibility finding, then, challengers must do more than suggest that compliance will be infeasible for some firms or in “a few isolated operations.”

The court also ruled that the rule met the economic feasibility standard in that it does not “threaten massive dislocation to, or imperil the existence of, the industry.”

The ruling cited OSHA’s explanation that many firms have only a handful of affected employees, and that recommended controls are often inexpensive systems integrated into hand tools.

“In light of OSHA’s explanation of the reason for the apparently low costs in certain construction industry groups, Industry’s bare argument that the costs are too low carries little weight.”

The rule also faced a legal challenge from labor unions, who objected to a provision that workers would receive medical surveillance only if they wore a respirator for 30 days for one employer.

Although the appeals court rejected the union’s challenge, the judges ruled that “OSHA failed to adequately explain its decision to omit medical removal protections from the Rule and remand for further consideration of the issue.”