National Public Radio is reporting that the Department of Labor is issuing a long-awaited and controversial rule aimed at better protecting workers from inhaling silica dust.

The new rule dramatically reduces the allowed exposure limits for workers in a slew of industries, from construction to manufacturing to fracking.

Around 2.3 million people in the U. S. are exposed to fine grains of silica on the job; inhaling the dust is one of the oldest known workplace hazards. Silica, which is basically sand, scars the lungs, causing diseases like silicosis and cancer.

Secretary of Labor Tom Perez says the existing rule that limits a worker's exposure to silica dust hasn't been changed since the early 1970s. And even back then, he adds, research showed the exposure limit didn't offer adequate protection.

"We've known for over 40 years that it needed to be strengthened, and it has taken 40 years to strengthen it," says Perez. "Many people who are going to work right now and breathing unacceptable levels of silica dust are in for a brighter future."

He says the current rule for construction sites caps exposure at 250 micrograms of silica per cubic meter of air.

"And the science says we need to be at 50," says Perez. "So that's what the final rule will say." That same updated exposure limit will apply to general industry as well, he adds, which will cut the current exposure limit in half.

Silica can be found in materials like concrete, brick, and stone. Busting up those materials sends silica dust into the air. Workers can also get exposed in manufacturing industries that use sand, such as foundries.

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