What is the OSHA permissible exposure limit (PEL) for asbestos as an 8-hour time-weighted average (TWA)?

• A. 0.1 f/cc 8-hr TWA
• B. 0.01 f/cc 8-hr TWA
• C. 1.0 f/cc 8-hr TWA
• D. 0.5 f/cc 8-hr TWA

Answer: (A)

Asbestos exposure is regulated using an 8-hour time-weighted average in fibers per cubic centimeter, meaning the average concentration over a full work shift should not exceed a specific limit. The official OSHA permissible exposure limit for asbestos, measured as an 8-hour TWA, is 0.1 f/cc. There is also a separate short-term exposure limit of 1.0 f/cc for a 15-minute period. So 0.1 f/cc as the 8-hour TWA is the correct limit, while the other numbers are either too high to be the PEL or represent a different, more protective value. The unit f/cc stands for fibers per cubic centimeter, reflecting how many asbestos fibers are present in a given volume of air.