Silica Construction Workplace exposures Respiratory conditions

'Long overdue'

OSHA aims to revise standards on worker exposure to silica

Silica exposure
Photo: Washington State Department of Transportation

Silicosis has plagued laborers for generations, but OSHA is proposing changes aimed at significantly decreasing the risk.

The lung disease, which has killed thousands of workers, is caused by exposure to airborne dust particles of crystalline silica – a mineral commonly used in a variety of industry applications, including concrete construction, metal castings and ceramics manufacturing. Respirable silica exposure also can lead to diseases such as cancer and tuberculosis.

At an Aug. 23 press conference, OSHA administrator David Michaels said the agency would issue a notice of proposed rulemaking to revise and strengthen current crystalline silica standards to help reduce worker exposure. The NPRM was published Sept. 12 in the Federal Register.

Dollars and cents

Annual cost* to employers is $657.9 million total:

  • $146.7 million – General industry and maritime
  • $511.2 million – Construction

Annual cost to average workplaces:

  • $1,242
  • $550 for firms with fewer than 20 employees

Net benefits*, annually for next 60 years:

  • $2.8-$4.7 billion

*In 2009 dollars
Estimated value of avoided fatalities or illnesses

Source: OSHA

“This proposal is long overdue,” Michaels said during the press conference. “OSHA’s current standards for protecting workers from silica exposure are dangerously out of date and do not adequately protect worker health.”

Proposal details

OSHA is proposing to revise two silica standards – one for construction and another for general industry and maritime – by setting a new permissible exposure limit. The current silica PEL – originally adopted in 1971 and based on research a decade older – is 100 micrograms per cubic meter of air on an 8-hour time-weighted average.

Under the proposal, the new PEL for construction, maritime and general industries would be 50 µg/m3 – a level NIOSH first recommended in 1974. An action level for the industries would be 25 µg/m3, a point at which employers would be required to conduct exposure monitoring.

When exposure levels are greater than the PEL, employers must limit worker access to those exposure areas and use dust control methods. For cases in which dust controls are unable to keep exposure levels below the PEL, employers are to provide workers with respirators.

The proposed rule also would require employers to offer medical exams every three years for workers exposed to the higher PEL for 30 days or more a year. The exams would include chest X-rays and lung function tests.

Additionally, workers are to be trained on silica hazards and ways to limit exposure, and employers must keep records of exposures and workers’ medical exams.


Life and death
  • 2.2 million U.S. workers are exposed to respirable silica each year.

Once fully implemented, the proposed rule would annually prevent an estimated:

  • 88 deaths
  • 1,600 new silicosis cases

Source: OSHA

As Michaels noted during the press conference, the proposed rule could change as it goes from the proposal stage to the final version, and he encouraged public participation. The Federal Register record will be open for comment until Dec. 11, and the agency will host public hearings beginning March 4 to solicit feedback from stakeholders. Parties interested in participating in the meeting should contact OSHA by Nov. 12.

OSHA is likely to receive a great deal of feedback, and not all of it will agree with the agency’s conclusions. Some industry stakeholders already have voiced objections to the lower PEL. The Washington-based National Industrial Sand Association supports the proposal to mandate monitoring and medical surveillance, but claims companies in the sand trade have “successfully protected their workers” under current limits, and no “proven need” for lowering the PEL exists.

The American Chemistry Council’s Crystalline Silica Panel agrees that the current PEL should be maintained, coupled with “reasonable and appropriate” monitoring. Strengthening the PEL, the panel said in a statement, would present problems.

Dust control methods

OSHA’s proposed crystalline silica rulemaking lists several methods for employers to control potentially deadly silica dusts:

  • Substitution – Replacing a toxic material with another substance
  • Isolation – Enclosing an operation by means of a physical barrier to restrict respirable dust from spreading through a workplace
  • Ventilation – Removing the air contaminant by capturing it at or near the source of emission
  • Dust suppression – Prevent airborne dust through various means, including applying liquid to the surface of a dust-generating material to ground the dust or dispensing moisture into a dust cloud to cause the respirable particles to drop

Source: OSHA

“Attempting to comply with the sharply reduced PEL presents enormous feasibility challenges for the many job-producing sectors where silica exposures may occur,” the panel said. “Furthermore, it is unclear how the proposed PEL could be enforced given that serious questions remain about the ability of laboratories to measure silica exposures accurately and reliably at such low concentrations.”

During the press conference, Michaels said reducing the PEL is “absolutely necessary” based on peer review risk assessments and studies showing a risk of silicosis and lung cancer at levels below the current PEL.

In response to industry concerns, Michaels said he did not believe measuring silica at the 50 µg/m3 level would be difficult. However, he said OSHA may propose delaying implementation of the rule for two years to allow growth in the market of laboratories accredited to conduct such analyses.

Regarding the comments alluding to the difficulty of complying with a reduced PEL, Michaels noted that viable solutions are currently available.

“Today, many employers across the country apply commonsense, inexpensive, and effective control measures that protect workers’ lives and lungs,” he said. “Tools that include these controls are readily available, and the rule is designed to give employers flexibility in selecting ways to meet the new standard.”

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