Science, Feasibility of OSHA’s Silica Proposal Debated

By Roy Maurer Mar 27, 2014

Industry stakeholders, worker advocates and public health experts are delivering testimony and cross-examining one another on proposed changes to the rules governing workplace exposure to crystalline silica.

Some say the Occupational Safety and Health Administration’s (OSHA) proposed rule to protect silica-exposed workers is decades overdue. The current permissible exposure limit (PEL) for respirable crystalline silica has not been updated since the agency’s creation in 1971. The current general industry PEL for quartz, the most common form of crystalline silica, is roughly 100 micrograms per cubic meter of air (100 ug/m3) as an eight-hour time-weighted average. The current PEL for quartz in construction and shipyards is approximately 250 ug/m3 and based on an outdated particle count sampling method, according to OSHA. The current PELs for two other forms of crystalline silica (cristobalite and tridymite) are one-half the values for quartz in general industry.

OSHA’s proposed new PEL—50 micrograms per cubic meter of air to cover all three silica types for all industry sectors—was first recommended by the National Institute for Occupational Safety and Health (NIOSH) in 1974.

The proposal also contains ancillary provisions—updated requirements for exposure assessment and control, respiratory protection, medical surveillance, hazard communication, and record-keeping—to match the lowered PEL.

More than 2 million workers are exposed to respirable crystalline silica each year, according to OSHA. Occupational exposure to crystalline silica happens during the cutting, sawing, drilling and crushing of concrete, brick, rock and stone.

NIOSH testified that extended occupational exposure to respirable crystalline silica can lead to the lung disease silicosis, as well as lung cancer, pulmonary tuberculosis, airways diseases, autoimmune disorders, chronic renal disease and other adverse health effects.

Activities historically associated with high rates of silicosis include sandblasting, sand-casting foundry operations, mining, tunneling, cement cutting, demolition, masonry work and granite cutting. OSHA estimates that the proposed rule will result in saving nearly 700 lives per year and will prevent 1,600 new cases of silicosis annually.

OSHA’s Science Questioned

Describing the proposed rule as neither technologically nor economically feasible, the U.S. Chamber of Commerce and the American Chemistry Council criticized much of the science underpinning OSHA’s silica proposal. The Chamber argued that OSHA did not provide adequate scientific justification for its rulemaking, cherry-picked data to fit its assertions, made false and improper risk assessments, used studies with sampling and analytical method errors, and neglected evidence relating to exposure-response thresholds used to ascertain safe and hazardous exposure levels, the long latency period of silicosis, and the downward trend of worker exposure under OSHA’s current PEL.

Yale School of Public Health professor Jonathan Borak, representing the Chamber, referenced Centers for Disease Control and Prevention (CDC) data on silicosis-related mortality, which shows a 93 percent decline from 1968 to 2002. More-recent CDC data indicate that the decline continued at least through 2007, resulting in 123 cases of silicosis-related mortality nationwide that year. Borak said OSHA’s belief that persistent but declining silicosis-related mortality is due to the current exposure level, and that the PEL therefore should be lowered, was wrong.

“We disagree. OSHA provides no empirical evidence of silicosis or silicosis-related mortality in those exposed to the current PEL, and OSHA provides no empirical data indicating that the current PEL is not protective,” he said.

Borak stressed that OSHA’s analysis ignores several relevant factors, including the fact that silicosis can take decades to develop. Due to widespread historical noncompliance before the introduction of the OSHA PEL, and significant noncompliance with the current PEL, “It can be expected that the vast majority of the silicosis-related deaths compiled by CDC were first exposed in the past, when exposure levels were substantially higher than currently,” he said.

He also said OSHA’s definition of “current exposures” is not very current. The OSHA exposure database relies mainly on data that are more than a decade old and sometimes on even older data. “Thus OSHA’s ‘current’ exposure data reflect conditions up to 30 years ago, and none is less than seven years old.”

Borak testified that OSHA’s definition of the silicosis latency period as being 10 to 30 years after first exposure significantly underestimates the actual latency for chronic silicosis, which he put at often exceeding 30 years.

He also questioned OSHA’s risk assessments, saying the agency’s sampling and analysis were problematic due to the “known variability and also quantifiable errors” associated with individual sampling pumps, samplers and laboratory analyses. “Inclusion of such exposure uncertainties would almost certainly reduce the statistical significance of the risk assessment findings and might alter their nominal results,” he said.

Tony Cox, a risk assessment specialist representing the American Chemistry Council, described OSHA’s quantitative risk assessment on which the proposed rule is based as “not ready for prime time. The answers and estimates it delivers are not trustworthy. You wouldn’t want to bet money on them. They might not be wrong. They might not be right.”

Cox said the risk assessment does not correct for well-known biases in modeling statistical associations between exposures and response. “As a result, OSHA has not demonstrated that there is any nonrandom association between crystalline silica exposure and adverse health responses at exposure levels at or below [the current PEL].”

He also testified that OSHA’s assessment lacks causal analyses. “It asserts causal conclusions based on noncausal studies, data and analyses; this is technically unsound," Cox said. "Throughout, OSHA has conflated association and causation, ignoring the fact that modeling choices can create findings of statistical associations that do not predict correctly the changes in health effects that would be caused by changes in exposures.” This lapse alone invalidates OSHA’s predictions and conclusions, he said.

Is OSHA’s Silica Exposure Proposal Feasible?

Much of the nonscientific debate centered on the economic and technological feasibility of the proposed rule, aspects that are required for any new regulation under federal law.

OSHA estimated that the proposed rule would cost $637 million annually over the first 10 years after enacted. The annual price per workplace comes out to about $1,250, with companies with fewer than 20 employees paying $550 each year, the agency said. Calculating in the estimated monetized benefits from preventing silicosis and related respiratory diseases, OSHA concluded that the proposed rule will generate net benefits of $4.6 billion annually.

Ronald Bird, a senior economist and regulatory analyst representing the Chamber, said OSHA’s economic feasibility assessment grossly underestimates the proposed rule’s cost to employers.

OSHA’s proposal would require employers to achieve complete compliance with the proposed PEL by retrofitting or rebuilding facilities to incorporate engineering controls within one year of the effective date of a final rule. Exposure assessment would be required within six months of the effective date. “There is a significant risk that the lack of available service providers or the resulting escalation in cost of their services will render compliance with the proposed rule within the schedule proposed by OSHA technically and economically infeasible,” Bird said.

Peg Seminario, safety and health director for the AFL-CIO, however, suggested that OSHA has not gone far enough to reduce silica in the workplace. “Overall, the cost to comply with a 50 ug/m3 exposure limit and other requirements in general industry and construction are less than 0.05 percent of industry revenues for the covered industries, and in no way threatens the viability of the industries impacted by the standard,” she said. “If anything, the feasibility analysis supports strengthening key provisions of the standard in order to protect workers from the significant risks of harm from silica that remain under the standard as proposed by OSHA.”

Seminario would like to see the final standard contain a number of additional protections, such as a trigger to begin medical surveillance sooner, more-frequent exams, additional training and required regulated areas at worksites.

But the question remained whether employers can actually implement the rule.

“As written, the proposed rule is probably not entirely technologically feasible for all employers,” said Kathy Seabrook, president of the American Society of Safety Engineers, citing OSHA’s admission that for some employers, even following the prescribed steps may not result in exposures below the rule’s limits.“Given the number of employers who currently do not meet the 100 ug/m3 PEL, many will likely have trouble complying with the new PEL, much less the action level [half the proposed PEL, the level that triggers exposure monitoring or exposure assessment], from an economic standpoint as well,” Seabrook said.

Nearly 85 percent of the 2.2 million workers exposed to silica work in construction. Speaking on behalf of the Construction Industry Safety Coalition, an alliance of 25 trade associations, Brad Hammock, leader of the workplace safety and health practice group at Jackson Lewis, said construction companies cannot meet the proposed PEL in most operations most of the time. “OSHA needs to rethink the way it regulates health standards in the construction industry in order to devise a workable rule for crystalline silica,” he said. “Relying on approaches used in previous health standards does not work here, given how ubiquitous silica is on construction worksites.”

Henry Chajet, a shareholder in the Washington, D.C., office of Jackson Lewis, testified for the Chamber that instead of lowering the PEL, OSHA could provide compliance assistance for current exposure limits, and could support new technology and policies favoring respirators and clean-filtered-air helmets, which he said provide full protection but “are not favored by OSHA’s outdated hierarchy of control policy.” OSHA’s hierarchy of hazard control is a system used to minimize or eliminate exposure to hazards and requires the use of all feasible engineering controls before personal protective equipment can be used.

The AFL-CIO strongly supports the hierarchy of controls in the silica standard. “There is long experience that the use of engineering and work practice controls is superior at protecting workers from hazardous exposures,” Seminario said. “There is no evidence to support that primary reliance on respiratory protection is as effective to protect workers against silica or other health hazards, and volumes of evidence to support the effectiveness of engineering and work practice controls.”

OSHA estimated that engineering and work practice controls will reduce exposures to less than the proposed PEL for the vast majority of workers. In construction, where the changing and mobile nature of the work create more-variable exposures, OSHA estimated that for more than 82 percent of all construction workers, engineering and work practice controls can reduce exposures to less than the proposed PEL.

Seminario cited studies used by OSHA that found that engineering and work practice controls such as wet-cutting methods and local exhaust ventilation “reduced exposures for most workers, in most jobs, most of the time” to levels below the proposed PEL. “The underlying evidence shows not only that the 50 ug/m3 standard is indeed technologically feasible, it also provides evidence that in some operations, the proper and consistent application of available control measures can reduce exposures to 25 ug/m3 or below.”

Kellie Vasquez, vice president of Holes Inc. and a member of the Concrete Sawing & Drilling Association, testified that wet cutting is not feasible with OSHA’s proposed “no visible dust” provision. “While ‘no visible dust’ is a lofty goal, it has no basis in reality in the construction environment. Rarely—if ever—will there be absolutely no visible dust emitted from a silica-generating activity with the use of wet methods or other engineering controls,” she said.

She also testified that compliance will be very difficult on a multiemployer worksite. “If one employer is conducting operations where visible dust is being emitted … it will be a significant challenge for an employer conducting operations alongside to demonstrate that its dust-control measures did not emit any visible dust.”

Critics of the proposed rule also found fault with OSHA’s proposed ancillary provisions, which Hammock said were “unworkable in the construction environment.”

For example, he said the exposure-monitoring provisions “are unworkable given the range of exposure conditions, environments, operations, materials and so on.” The establishment of regulated areas or written access control plans “also does not work on most construction sites due to multiple operations and environmental conditions that are constantly shifting and changing.”

Public Health Groups Support Proposal

Rosemary Sokas, chair of the Department of Human Science at the Georgetown University School of Nursing and Health Studies, testified in favor of a stronger proposal, asking, like Seminario, for more medical surveillance and more-frequent exams. Speaking on behalf of the American Public Health Association, she also called for OSHA to require that employers post warning signs in regulated areas, update exposure-control methods for construction operations to reflect improvements in dust-control technology and prohibit the use of silica sand entirely in sandblasting work.

Other public health organizations, including the American Thoracic Society, the American Medical Association and the American Cancer Society (ACS), endorsed OSHA’s proposed rule.

“OSHA presents a clear and compelling well-supported rationale for the proposed standard, and we urge that it be adopted promptly,” the ACS said, adding that “OSHA’s analysis indicates that reducing the PEL results in benefits that substantially exceed costs.”

Hearings on the proposed silica standard are set to conclude April 4, 2014.

Roy Maurer is an online editor/manager for SHRM.

Follow him @SHRMRoy


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