The study of silica: Part one

The federal government's strict silica regulation has pushed NRCA into action

Editor's note: The following article is part one of a two-part series. Part two will be published in the March issue and address roofing exposures to silica in more detail.

The Occupational Safety and Health Administration (OSHA) began fully enforcing its new regulation regarding worker exposure to respirable crystalline silica (RCS) Oct. 23, 2017. In December 2017, a three-judge panel of the U.S. Court of Appeals for the D.C. Circuit rejected oral arguments from industry groups that had filed suit against OSHA to stop the RCS rule from being implemented. As a result, OSHA's enforcement remains in full swing.

According to OSHA, about 2.3 million workers are exposed to RCS in their workplaces. The at-risk workforce comprises about 2 million construction workers who drill, cut, crush and/or grind silica-containing materials such as concrete and stone. OSHA claims the final rule will save more than 640 lives and prevent more than 900 new cases of silicosis each year though some industry groups, including NRCA, dispute these projections.

Silica is the chemical compound silicon dioxide (SiO2). Sand, a key component in many building products such as mortar, clay and concrete tiles, pavers and brick, mainly is composed of silica in the form of quartz. Hazards develop when materials containing silica are cut, drilled and/or ground in a way that produces RCS. This most often is done with powered saws or grinders with diamond blades or silicon carbide-cut wheels that produce inhalable airborne particles.

RCS refers to inhaled particles about 10 microns in size or less that can get into the oxygen-exchange portions of the lungs and cause health problems; larger particles do not travel that deeply into the lungs and are purged by the body's natural actions. Respirable particles remain in the lungs and cause permanent scarring of lung tissue, making breathing increasingly more difficult—an occupational disease known as silicosis that often does not manifest itself until many years after exposure. According to the American Lung Association, silicosis also increases the risk of other lung issues such as tuberculosis, lung cancer and chronic bronchitis.

The rule

The former OSHA construction regulation 29 CFR §1926.55 addressing silica as an airborne contaminant under the Mineral Dust Table was adopted in 1971. However, the formula for determining worker exposure under the table was based on an obsolete sampling method that rendered the regulation ineffective. The agency set about crafting a new regulation for occupational exposure to RCS that first was proposed to the public in September 2013.

The construction rule sets out the following key features:

  • Establishment of an action level and a permissible exposure limit (PEL) for worker exposures
  • Specified exposure control methods for construction tasks listed in what OSHA refers to as Table 1 that eliminate the requirement for initial exposure monitoring
  • The requirement for a written exposure control plan
  • Medical surveillance for workers required to wear a respirator for 30 or more days in a year
  • Silica hazard communication to workers
  • Use of objective data to assess worker exposure to silica

Action level and PEL

Under OSHA's rule, an employer must ensure no worker is exposed to an RCS concentration in excess of the PEL of 50 micrograms per cubic meter (m3) of air calculated as an eight-hour time-weighted average. The employer also is obligated to assess the exposure of any worker who is or reasonably may be expected to be exposed to a level of RCS at or above the action level of 25 micrograms/m3 of air calculated as an eight-hour time-weighted average.

The PEL of 50 micrograms reflects a significantly more protective (lower) exposure level than was permitted under the former formulaic calculation of about 25 micrograms/m3 of air.

Performing air monitoring of workers to assess exposure to RCS is a costly feature of the regulation. Two other elements of the rule can act to minimize the administrative burdens and financial effects of the RCS rule: the provision for objective data and use of the specified exposure control methods under Table 1.

Table 1

Under 29 CFR §1926.1153(c), OSHA sets out specified exposure control methods for a variety of construction tasks. For those tasks set out in Table 1, if an employer implements the engineering controls and respiratory protection listed for a specific task, the employer would be considered in compliance and initial exposure monitoring would not be required.

As an example, Table 1 requires an integrated water delivery system that continuously feeds water to the blade of a handheld power saw used to cut silica-containing material. For outdoor use of four hours or less, Table 1 does not require a respirator be worn by the operator with the water delivery to the blade. However, if cutting exceeds four hours, a respirator with an assigned protection factor (APF) of 10 must also be used.

The National Institute for Occupational Safety and Health (NIOSH) notes in the 2004 Respirator Selection Logic that filtering face piece respirators (dust masks) are available with an APF of 10 if the filter medium protects against the particulate in question. This is determined by the designation of the filtering face piece as an N, P or R type. N is not resistant to oil particles; P is oil-proof; and R is resistant to oil. In NRCA's view, using water to control dust on roofs, particularly steep-slope roofs, remains an area of substantial concern for operator safety, and this is an area that requires increased vigilance by contractors to ensure worker safety.

Another Table 1 task is the use of a handheld grinder for mortar removal, for example, to facilitate counterflashing installation. To comply with the engineering controls, the grinder must be equipped with a shroud and dust-collection system operated according to the manufacturer's instructions. OSHA specifies the minimum airflow, filter efficiency and type in the table. In addition, an operator using a grinder with the described dust-collection attachment must wear a respirator with an APF of 10 when grinding work is performed for four hours or less and a respirator with an APF of 25 when grinding is performed for more than four hours.

NIOSH lists two types of APF 25 respirators in its selection logic: Any powered air-purifying respirator equipped with a hood or helmet and a high-efficiency filter and any continuous flow supplied-air respirator equipped with a hood or helmet. Extending the time a roofing worker uses a grinder for mortar joints in excess of four hours triggers required use of the more efficient yet cumbersome and more expensive types of respirators.

Written exposure control plan

When workplace tasks involve RCS exposure, a contractor must develop a written exposure control plan describing the engineering controls, work practices and respiratory protection that will be used to protect workers during performance of those tasks. The contractor also must:

  • Describe in the plan the housekeeping measures that will be used to minimize worker exposure to RCS
  • Describe procedures to restrict access to work areas when necessary and minimize the number of workers exposed and their exposure levels
  • Review and evaluate the plan's effectiveness at least annually
  • Make the plan available for examination and copy workers, their representatives and/or OSHA
  • Designate a competent person to inspect job sites, materials and equipment on a frequent, regular basis to implement the plan

Medical surveillance

The rule's medical surveillance requirement is tied to the days when a worker had to use a respirator. If respirator use is required for 30 or more days during a year, a contractor must make sure a number of medical examinations and procedures take place. For example, an initial examination must include a focus on the worker's medical and work history, physical exam, chest X-ray, pulmonary function test and tuberculosis test. OSHA requires an initial examination as a baseline evaluation to be performed within 30 days after the worker's initial assignment. A contractor must make sure a physician or other licensed health care professional is informed of the worker's duties as they relate to silica exposure, the levels of silica the worker has been or may be exposed to, the type of personal protective equipment used by the worker, and information from employment-related medical exams previously provided to the worker and within the control of the contractor.

A contractor also must ensure the worker gets a report from the health care professional within 30 days of the exam and the results of the exam are explained to the worker. A contractor must obtain a medical opinion from the health care professional within 30 days of a worker's medical examination.

Silica hazard communication

OSHA requires a contractor include RCS in a hazard communication program that specifically addresses cancer, lung, immune system and kidney issues related to exposure. A contractor must make sure workers demonstrate knowledge and understanding of hazards related to silica exposure, tasks in the workplace that can result in exposure, control measures the contractor has implemented to protect workers, provisions of the OSHA rule, identity of the competent person who will inspect job sites to implement the written exposure control plan, and the purpose and features of the medical surveillance program.

Objective data

The rule allows for the use of objective data to exempt a contractor from air-monitoring requirements and provide a basis for respirator selection. OSHA notes reliance on objective data is intended to provide the same degree of assurance that air monitoring of worker exposures through personal breathing samples does, so it comes with a specific record-keeping requirement.

The rule requires objective data reflect workplace conditions closely resembling the processes, material types, control methods, work practices and environmental conditions as in the contractor's current operations. Industry data are acceptable under the rule's definition of the term. As to record keeping, a contractor must maintain a record of the silica-containing material; the data's source; test protocol and results; a description; and other details regarding the process, task or activity on which the data are based. Because OSHA views objective data similar to employee exposure records, the rule requires the data be maintained for at least 30 years.

NRCA action

In summer 2017, in conjunction with a number of its affiliate organizations, NRCA started collecting personal breathing zone and area samples on select roofing job sites with the assistance of a number of NRCA members. The goal established by NRCA's Silica Task Force was to catalog details of roofing tasks and processes that could form the basis for industrywide objective data and possibly reduce the burden of the regulation on roofing contractors.

The result is an objective data collection that reflects the fact that a majority of roofing work does not involve levels of exposure to RCS that are dangerous to workers. The main roofing tasks the sampling focused on were removing and installing asphalt shingle, polymer-modified bitumen and built-up roof systems. In addition, data is available for operations such as drilling into masonry, cutting of clay and concrete tiles and pavers, installing and removing gravel, installing gypsum roof boards and other roofing tasks. NRCA is maintaining the collection as a living document as areas of potential exposure are discovered and supplemental results on sampled roofing tasks are reported.

Since initial publication of the proposed silica rule, NRCA has been encouraging OSHA to tailor the requirements of any rule with an eye toward the more significant hazards roofing workers face, specifically falls. The fall-hazard issue remains NRCA's primary concern with enforcing the RCS rule. NRCA wants to sustain that focus going forward to ensure roofing workers are not only protected from the health hazards related to silica but also kept secure from fall hazards compounded by provisions of the RCS rule.

Harry Dietz is an NRCA director of enterprise risk management.

To read more about this topic, see "Understanding a complex killer," August 2005 issue.

NRCA resources

NRCA has developed a sample written silica exposure control plan for members to use to develop their company-specific plans required by the rule. The sample plan is easily edited to allow company-specific information to be set out relating to exposures their workers may encounter and procedures the company has in place to address respirable crystalline silica. In addition, NRCA offers a PowerPoint® presentation in English and Spanish for the rule's hazard-communication worker training requirement.

Both resources are available to NRCA members under the "Safety and insurance" tab at Please note your member login information will be needed to access the documents.



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