The U.S. Occupational Safety and Health Administration has released its final silica rule, which will lower the amount of silica dust workers can be exposed to and mandate certain controls to limit exposure.

The Occupational Exposure to Respirable Crystalline Silica rule will reduce the permissible exposure for crystalline silica to 50 micrograms per cubic meter of air, averaged over an eight-hour shift, from the current 100 micrograms per cubic meter of air standard, OSHA said Thursday in a statement.

Employers will also be required to use engineering controls such as water or ventilation and work practices to limit worker exposure, provide respiratory protection when controls are not able to limit exposures to the permissible level, limit access to high exposure areas, train workers and provide medical exams to highly exposed workers, according to the agency.

The final rule is written as two standards: one for construction and one for general industry and maritime.

Employers covered by the construction standard have until June 23, 2017, to comply with most requirements, according to the agency. About 2 million construction workers are exposed to respirable crystalline silica in more than 600,000 workplaces, and OSHA estimates that more than 840,000 of these workers are exposed to silica levels that exceed the new permissible exposure limit, the agency said in the statement.

Employers covered by the general industry and maritime standard have until June 23, 2018, to comply with most requirements, with additional time provided to offer medical exams to some workers and for hydraulic fracturing employers to install dust controls to meet the new exposure limit. About 300,000 workers in operations such as brick manufacturing, foundries and hydraulic fracturing are exposed to silica dust, according to the agency.

“The previous exposure limits were outdated and did not adequately protect workers,” Assistant Secretary of Labor for Occupational Safety and Health David Michaels said in the statement. “Limiting exposure to silica dust is essential. Every year, many exposed workers not only lose their ability to work, but also to breathe. Today, we are taking action to bring worker protections into the 21st century in ways that are feasible and economical for employers to implement.”

The final rule will save more than 600 lives annually and prevent more than 900 new cases of silicosis each year when it becomes fully effective, OSHA said in the statement.