This memorandum to Regional Administrators lays out how OSHA enforces Section 5(a)(1) of the OSH Act — the General Duty Clause — for respiratory hazards from substances that have no OSHA Permissible Exposure Limit.
To prove a General Duty Clause violation, OSHA must establish all four elements: (1) the employer failed to keep the workplace free of a hazard to which employees were exposed, (2) the hazard was recognized, (3) the hazard was causing or likely to cause death or serious physical harm, and (4) feasible and useful methods to correct the hazard existed. Critically, the memo stresses that 5(a)(1) citations are not based solely on evidence that a measured exposure exceeded a recommended occupational exposure limit, such as an ACGIH Threshold Limit Value.
The memo details what evidence supports each element: air sampling, workplace observations, and documentation of controls for exposure (and OSHA notes a proper respirator program substantially weakens enforcement prospects); employer knowledge from complaints, injury logs, and SDSs, or industry recognition through trade associations, NIOSH, or ACGIH guidance for recognition; illness or injury evidence or expert peer-reviewed studies for serious harm (measured exposure alone is insufficient); and typically expert testimony that feasible abatement measures exist.
When evidence doesn't support all four elements, compliance officers should issue a Hazard Alert Letter (HAL) recommending exposure control improvements rather than a citation. The memo includes a sample HAL for 1-bromopropane exposure, recommending engineering controls, administrative practices, PPE, and hazard communication training compliance (29 CFR 1910.1200).