7.1 Respirable Crystalline Silica (1926.1153)

Respirable Crystalline Silica (29 CFR 1926.1153)

Respirable crystalline silica is one of the most widespread and severe occupational hazards in construction. Crystalline silica is a common mineral found in materials used on construction sites, including sand, stone, concrete, brick, mortar, and block. When these materials are cut, drilled, ground, or crushed, they release microscopic dust particles. These particles, which are at least 100 times smaller than ordinary beach sand, are known as respirable crystalline silica. Because of their tiny size, they bypass the body's natural filtration systems in the nose and throat and travel deep into the lungs, where they can cause permanent, irreversible lung damage.

Health Hazards Associated with Silica Exposure

Inhaling respirable crystalline silica can lead to several serious, debilitating, and potentially fatal diseases:

• Silicosis: An irreversible and progressive lung disease where silica particles cause scar tissue to build up in the lungs, reducing the lungs' ability to take in oxygen. Silicosis exists in three forms:
  • Chronic Silicosis: Occurs after 10 or more years of low-to-moderate exposure. It is the most common form.
  • Accelerated Silicosis: Develops within 5 to 10 years of high exposure and progresses rapidly.
  • Acute Silicosis: Develops within weeks to a few years after extremely high exposure. It causes severe shortness of breath and can lead to death within months.
• Lung Cancer: Respirable crystalline silica is classified as a known human carcinogen.
• Chronic Obstructive Pulmonary Disease (COPD): Including chronic bronchitis and emphysema.
• Kidney Disease and Autoimmune Diseases: Studies have linked silica exposure to rheumatoid arthritis, systemic lupus, and chronic kidney disease.

OSHA Exposure Limits: Action Level and PEL

OSHA sets strict limits on the amount of respirable crystalline silica that workers can be exposed to in the air. These limits are measured as an 8-hour time-weighted average (TWA):

• Action Level (AL): 25 micrograms per cubic meter of air (25 μg/m³). This level triggers requirements for exposure monitoring, medical surveillance, and training.
• Permissible Exposure Limit (PEL): 50 micrograms per cubic meter of air (50 μg/m³). Employers must ensure that no employee is exposed to airborne concentrations above this limit.

Exposure Assessment Options

For operations not covered by Table 1, or where Table 1 controls are not fully implemented, employers must assess the exposure of each employee who may be exposed above the Action Level. The standard provides two options:

1. Performance Option: The employer assesses exposure using a combination of air monitoring data and/or objective data (e.g., historical studies, industry-wide surveys) sufficient to accurately characterize employee exposure.
2. Scheduled Monitoring Option: The employer performs personal air monitoring to represent exposure for each shift, job classification, and work area. The frequency of monitoring is determined by the results:
   • If initial results are below the Action Level (< 25 μg/m³), monitoring can be discontinued.
   • If results are at or above the Action Level but at or below the PEL (25–50 μg/m³), monitoring must be repeated every 6 months.
   • If results are above the PEL (> 50 μg/m³), monitoring must be repeated every 3 months.
   • The employer may discontinue monitoring if two consecutive measurements, taken at least 7 days apart, show exposures below the Action Level.

Table 1: Specified Exposure Control Methods

To simplify compliance for construction employers, OSHA developed Table 1 of 29 CFR 1926.1153. Table 1 matches 18 common construction tasks with specific engineering controls, work practices, and respiratory protection requirements. If an employer fully and properly implements the controls specified in Table 1, they are exempt from the requirements to conduct exposure monitoring and meet the PEL for those tasks.

Key Table 1 Tasks and Control Measures

Exam Trap: Pay close attention to the duration (4 hours or less vs. more than 4 hours) and location (outdoors vs. indoors/enclosed). For handheld power saws, working outdoors for 4 hours or less requires no respirator, but working outdoors for more than 4 hours requires an APF 10 respirator (such as an N95). Indoors, an APF 10 is required regardless of duration.

Written Exposure Control Plan

Every construction employer with silica exposure must establish, implement, and maintain a Written Exposure Control Plan. The plan must contain the following components:

1. A description of the tasks in the workplace that involve exposure to respirable crystalline silica.
2. A description of the engineering controls, work practices, and respiratory protection used to limit employee exposure for each task.
3. A description of the housekeeping measures used to limit exposure (such as wet sweeping or HEPA vacuuming).
4. A description of the procedures used to restrict access to work areas, when necessary, to minimize the number of employees exposed.

The Role of the Competent Person

The employer must designate a competent person to make frequent and regular inspections of job sites, materials, and equipment. For the silica standard, the competent person is defined as an individual who:

• Is capable of identifying existing and foreseeable silica hazards in the workplace.
• Has authorization to take prompt corrective measures to eliminate them.
• Is responsible for implementing the written exposure control plan.

Housekeeping Requirements

Dust control is a critical aspect of silica hazard prevention. The standard prohibits certain housekeeping practices that lift dust into the air:

• Dry Sweeping and Dry Brushing: Prohibited unless wet sweeping, HEPA-vacuuming, or other methods that minimize airborne dust are infeasible.
• Compressed Air Cleaning: Prohibited for cleaning surfaces or clothing unless the compressed air is used in conjunction with a ventilation system that effectively captures the dust cloud.

Medical Surveillance

The employer must provide medical surveillance at no cost to employees who are required by the standard to use a respirator for 30 or more days per year. The surveillance must include:

• Medical and Work History: Focus on prior exposures, respiratory symptoms, and smoking history.
• Physical Examination: Special emphasis on the respiratory system.
• Chest X-Ray: Evaluated by a certified "B Reader" to detect signs of silicosis.
• Spirometry Test: To measure lung function, specifically Forced Vital Capacity (FVC) and Forced Expiratory Volume in 1 second (FEV1).
• Tuberculosis (TB) Testing: At the initial exam, as silicosis increases susceptibility to TB.
• Frequency: Offered within 30 days of initial assignment, and at least once every 3 years thereafter.