U.S. to set limits on silica exposure first recommended half a century ago

Most people know silica as the mysterious contents of desiccation packets found in vitamin bottles, high-end leather purses, clothing, and other items. But for miners and other stone cutters, silica is a serious health hazard, and new rules announced on Tuesday by a U.S. government agency set strict limits on how much of the mineral they can be exposed to.

The rules, announced by the U.S. Labor Department’s Mine Safety and Health Administration, limit permissible exposure to crystalline silica to 50 micrograms per cubic meter of air for a full eight-hour shift. The action level, or the amount warranting remedial action, is 25 micrograms per cubic meter of air. The lower or action level is the one at which monitoring of worker exposure is initiated and employers are expected to control further exposure; the higher level is the maximum exposure permitted and the level above which people would have to stop working. 

A statement released by the agency estimated that the rules will prevent over 1,000 deaths and nearly 4,000 cases of silica-related illness.

The new regulations, which will be officially published on April 18 and take effect on June 17, follow a 1974 recommendation that advocates have for decades asked the government to adopt. Until now, the limit had been set to 100 micrograms of silica per cubic meter of air, double the new amount.

Crystalline silica is one of the most common minerals on earth. It can be found in sand, stone, and soil, and its dust is common in coal and other types of mining. It is also a carcinogen, and overexposure can cause severe lung issues, in particular silicosis, a condition in which small silica particles scar the lungs and reduce their ability to take in oxygen. This is a chronic, often debilitating condition that can be fatal, and it occurs after exposure to high concentrations of silica crystals, with symptoms emerging up to a decade later. Silica exposure can also increase the risk of tuberculosis, lead to lung cancer, and is linked to black lung disease, a deadly condition that can make breathing difficult and which has affected thousands of miners in the past decade in Virginia and Kentucky.

“It is unconscionable that our nation’s miners have worked without adequate protection from silica dust despite it being a known health hazard for decades,” said Julie Su, the labor department’s acting secretary, in a statement announcing the rules.

The regulations also require periodic free health examinations for miners and state that mine operators are in charge of monitoring silica exposure and preventing overexposure. “These kinds of regulations are low-hanging fruits to save lives. I think that the fact that we’re actually moving forward with them is great, but this should have been taken care of decades ago,” said Bobby Mahajan, a pulmonologist and spokesperson for the American Lung Association.

He added that there needs to be more stringent use of masks and protective equipment to limit silica’s effects, not just in mines but also in construction sites and wherever people are engaged in stone cutting.

Mahajan said it’s often the workers who avoid using masks or respirators, which indicates a lack of awareness about the seriousness of silica exposure. “It is really important to educate workers, but also educating the companies that utilize these workers to protect them appropriately,” he said.

Mining organizations have welcomed at least part of the rule. “We are still reviewing the rule and need to discuss it with our members, but we fully support the new, lower limits contained in the rule,” said Conor Bernstein, a spokesperson for the National Mining Association, in an email to STAT. However, the organization thinks there are important elements still missing in the rule, in particular when it comes to enforcement and the adoption of protective equipment. “Our recommendations on the draft rule included allowing for the use of administrative controls and personal protective equipment (PPE) to supplement and enhance engineering controls; unfortunately, those recommendations were not included in the final rule,” said Bernstein.