Permissible Exposure Limit

OSHA mandates a permissible exposure limit (PEL) for exposure to silica. The PEL specifies the maximum amount of airborne crystalline silica that an employee may be exposed to during an eight-hour work shift.

The crystalline silica PEL for the construction industry is expressed in terms of millions of particles per cubic foot (mppcf) of air. Previously, the PEL was measured in milligrams per cubic meter (mg/m³) of air. Since the construction PEL is now expressed in terms of millions of particles per cubic foot of air, the results of the sampling must be converted to a value that is equivalent to milligrams per cubic foot.

Needing a formula for converting from milligrams per cubic meter (mg/m³) of air to millions of particles per cubic foot (mppcf) of air OSHA requested help from the National Institute for Occupational Safety and Health (NIOSH). NIOSH recommended a conversion factor that results in 0.1 mg/m³ of respirable silica dust equaling 1 mppcf of dust. OSHA determined that this conversion factor will be applied to sampling results in order to determine silica exposure in construction settings.

There are several other relevant OSHA regulations, including respiratory protection, posting of warning signs, housekeeping, reporting of occupational illnesses, abrasive blasting, personal protective equipment, and training. OSHA also has rules about how employers should communicate with their workers about hazards, and requires that certain safety and health programs should be established and maintained. OSHA also requires access to employee exposure and medical records.

To learn more about Construction Silica visit our Construction Silica Safety Online Training web page.