Full Answer Section

Based on Establishing Authority and Legal Enforceability:

• Permissible Exposure Limits (PELs): These are legally enforceable limits established by governmental regulatory agencies, such as the Occupational Safety and Health Administration (OSHA) in the United States. Employers are required to comply with PELs, and failure to do so can result in penalties.
• Threshold Limit Values (TLVs): These are recommendations established by the American Conference of Governmental Industrial Hygienists (ACGIH). TLVs are health-based guidelines and are not legally enforceable standards themselves, but they are widely recognized and often adopted or referenced by regulatory bodies and industrial hygiene professionals worldwide.
  • TLVs also include TWA, STEL, and Ceiling designations.
• Recommended Exposure Limits (RELs): These are recommendations established by the National Institute for Occupational Safety and Health (NIOSH) in the United States. Similar to TLVs, RELs are based on scientific data and are provided to OSHA for consideration in developing legally enforceable standards.
• Workplace Exposure Limits (WELs): Used in the UK, these are GB occupational exposure limits approved by the Health and Safety Executive (HSE) and are legally binding under the Control of Substances Hazardous to Health Regulations (COSHH).
  • Within WELs, there are sometimes Occupational Exposure Standards (OES) for substances where a safe threshold can be identified, and Maximum Exposure Limits (MEL) for substances with serious health implications where a safe threshold cannot be set (e.g., carcinogens). For MELs, exposure must be reduced to as low as reasonably practicable.
• Indicative Occupational Exposure Limit Values (IOELVs) and Binding Occupational Exposure Limit Values (BOELVs): These are established at the European Union level through directives. IOELVs are non-binding values that Member States should consider when setting their national OELs, while BOELVs are legally binding and must be implemented by Member States.
• Other Country-Specific OELs: Many other countries have their own specific terms and lists of OELs established by their respective regulatory agencies (e.g., MAK values in Germany, VLE in France).