The Occupational Safety and Health Administration (OSHA) will begin enforcement of its final crystalline silica standard on Saturday, September 23, after a three-month delay.

The silica rule, which has been in the works since 2013, is intended to limit workers’ exposure to respirable crystalline silica. It reduces the permissible exposure limit (PEL) for workers to 50 micrograms per cubic meter of air, averaged over an eight-hour shift. It also requires employers to implement engineering controls, offer medical exams and develop control plans related to the issue.

According to OSHA, as many as 2.3 million workers, many in the construction and manufacturing industries, will be affected by the rule.

“OSHA estimates that the rule will save over 600 lives and prevent more than 900 new cases of silicosis each year, once its effects are fully realized. The Final Rule is projected to provide net benefits of about $7.7 billion, annually,” says the OSHA silica website.

The rule was originally set to be enforced within the construction industry starting June 23 of this year, but was delayed for three months to allow OSHA to conduct additional outreach and provide educational materials and guidance for affected employers.

Long-term exposure to respirable crystalline silica can cause lung cancer, silicosis, chronic obstructive pulmonary disease and kidney disease, according to OSHA.

U.S. Department of Labor’s acting deputy assistant secretary Thomas Galassi issued a memorandum about the upcoming enforcement on September 20.

“During the first 30 days of enforcement, OSHA will carefully evaluate good faith efforts taken by employers in their attempts to meet the new construction silica standard,” said Galassi. “OSHA will render compliance assistance and outreach to assure that covered employers are fully and properly complying with its requirements…If, upon inspection, it appears an employer is not making any efforts to comply, OSHA’s inspection will not only include collection of exposure air monitoring performed in accordance with Agency procedures, but those employers may also be considered for citation. Any proposed citations related to inspections conducted in this time period will require National Office review.”

Several construction coalitions filed a petition against the rule in April 2016. According to Lexology, the U.S. Court of Appeals for the D.C. Circuit will hear their arguments on September 26.

The petitioning organizations noted in April 2016 that the industry “presented substantial evidence that OSHA’s proposed PEL was technologically and economically infeasible” but that the agency moved forward with the PEL anyway.