What Is a PEL?

A permissible exposure limit, or PEL, is the maximum amount of a regulated airborne contaminant that a worker may be exposed to under OSHA standards. PELs are typically measured as an eight-hour time-weighted average (TWA), which reflects a worker’s average exposure over a standard work shift. Some substances may also have ceiling limits or short-term exposure limits that cannot be exceeded during specific periods.

PELs are important compliance benchmarks, but they should not always be treated as a guarantee of safe exposure. Many OSHA PELs were established decades ago, and OSHA has acknowledged that some may not reflect the latest health science. For this reason, many manufacturers also consider more protective guidance from organizations such as ACGIHand NIOSH when setting internal air quality goals.

Examples of OSHA PELs for selected industrial contaminants include:

• Cadmium: 0.005 mg/m³ as an 8-hour TWA
• Hexavalent chromium: 5 µg/m³ as an 8-hour TWA
• Lead: 0.05 mg/m³ as an 8-hour TWA
• Nickel metal and insoluble compounds: 1.0 mg/m³ as an 8-hour TWA
• Manganese compounds and fume: 5 mg/m³ ceiling limit

Because exposure limits vary by substance, compound, industry and exposure basis, employers should verify the applicable OSHA standard for each contaminant present in the facility. Air quality testing, exposure monitoring and industrial hygiene evaluations can help manufacturers determine whether worker exposures are below applicable PELs and whether additional controls are needed.