Silica Exposure in the Workplace: Understanding OSHA Standards and Control Methodology

Silica is a naturally occurring mineral found in sand, rock, and soil. It is a common component of construction materials such as concrete, brick, and mortar, and is also used in a variety of industrial products such as glass, ceramics, and electronics. While silica is not harmful when it is in its solid form, it can be dangerous when it is inhaled in the form of fine dust or fumes.

Exposure to silica dust can lead to a range of respiratory problems, including silicosis, a lung disease that can cause difficulty breathing, coughing, and chest pain. It can also increase the risk of lung cancer and other respiratory diseases.

To protect workers from the dangers of silica exposure, the Occupational Safety and Health Administration (OSHA) has established specific standards for the construction and general industry sectors. It's important for employers to understand the differences between these standards and to implement the appropriate controls to protect their employees.

General Industry OSHA Standards

OSHA's general industry standard for silica exposure, 29 CFR 1910.1053, applies to all occupational exposures to respirable crystalline silica except construction work, agricultural operations, and exposures that result from the processing of sorptive clays (1910.1053(a)(1)). Paragraphs (a)(2) and (a)(3) add further exceptions, including where the employer has objective data demonstrating that employee exposure will remain below 25 μg/m3 as an 8-hour time-weighted average under any foreseeable conditions (1910.1053(a)(2)). The standard sets two exposure levels, both calculated as an 8-hour time-weighted average: a permissible exposure limit (PEL) of 50 micrograms per cubic meter of air (μg/m3) and an action level of 25 μg/m3. The standard requires employers to take the following actions:

Assess the exposure of each employee who is or may reasonably be expected to be exposed at or above the action level (1910.1053(d)(1)).
Ensure that no employee is exposed above the PEL (1910.1053(c)).
Use engineering and work practice controls, such as ventilation systems, to reduce and maintain exposure to or below the PEL, unless the employer can demonstrate that such controls are not feasible (1910.1053(f)(1)).
Establish a regulated area wherever exposure is, or can reasonably be expected to be, above the PEL (1910.1053(e)(1)).
Provide respirators where the standard requires them, such as where feasible controls are not enough to reduce exposure to or below the PEL (1910.1053(g)(1)).
Establish and implement a written exposure control plan (1910.1053(f)(2)).
Make medical surveillance available at no cost to each employee who will be exposed at or above the action level for 30 or more days per year (1910.1053(i)(1)(i)).
Train workers on the health hazards of silica, the tasks that could expose them, and the measures in place to protect them (1910.1053(j)(3)).

Construction OSHA Standards

OSHA's construction standard for silica exposure, 29 CFR 1926.1153, uses the same PEL of 50 μg/m3 and the same action level of 25 μg/m3 as the general industry standard. The main difference is in how employers comply:

For each employee doing a task listed in Table 1 of the standard, fully and properly implement the engineering controls, work practices, and respiratory protection that Table 1 specifies for that task, unless the employer assesses and limits the employee's exposure under paragraph (d) instead (1926.1153(c)(1)).
For tasks not listed in Table 1, or where the Table 1 measures are not fully and properly implemented, assess the exposure of each employee who is or may reasonably be expected to be exposed at or above the action level, and use engineering and work practice controls, such as water spraying systems, to reduce and maintain exposure to or below the PEL unless the employer can demonstrate that such controls are not feasible, supplementing them with respiratory protection where they are not sufficient (1926.1153(d)).
Establish and implement a written exposure control plan (1926.1153(g)(1)), and designate a competent person to make frequent and regular inspections of job sites, materials, and equipment to implement the plan (1926.1153(g)(4)).
Make medical surveillance available at no cost to each employee who will be required by the standard to use a respirator for 30 or more days per year (1926.1153(h)(1)(i)).
Ensure that each covered employee can demonstrate knowledge and understanding of the health hazards of silica, the tasks that could expose them, and the measures in place to protect them (1926.1153(i)(2)(i)).

Personal Protective Equipment (PPE)

PPE is a key element of any silica exposure control plan. It includes items such as respirators, face masks, and goggles that are designed to protect workers from inhaling silica dust and fumes. When selecting PPE, it's important to choose equipment that is appropriate for the task at hand and fits the worker properly.

Control Methodology

There are several approaches that can be taken to control silica exposure in the workplace. The most effective method is engineering controls, which involve altering the work environment or process to reduce the amount of silica in the air. This can include using ventilation systems to exhaust silica-containing dust, enclosing work processes to contain the dust, and using water or other wetting agents to suppress dust.

Another important control method is the use of administrative controls, which involve changing work practices to reduce exposure. This can include rotating workers to different tasks, limiting the amount of time spent on high-exposure tasks, and providing training to workers on how to minimize exposure.

In some cases, PPE may also be necessary to protect workers from silica exposure. This can include respirators, which are specialized masks that fit over the nose and mouth and filter out silica particles. Other types of PPE that may be used include face/eye protection and other protective clothing.

It's important for employers to carefully assess the risks of silica exposure in their workplace and to implement the appropriate controls to protect their workers. This may involve a combination of engineering controls, administrative controls, and PPE, and should be outlined in a written exposure control plan. By taking these steps, employers can help prevent the serious respiratory problems that can result from silica exposure and ensure the health and safety of their workers.

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