Understanding OSHA PEL: A Guide to Workplace Safety Limits

occupational exposure limits in production facility

Exposure to hazardous materials in the workplace can lead to a variety of health problems, ranging from minor irritation to chronic illness. The Occupational Safety and Health Administration (OSHA) plays a vital role in establishing and enforcing regulations to protect workers from these dangers. One key tool in this effort to limit exposure, is the Permissible Exposure Limit (PEL).

According to the Bureau of Labor Statistics, in 2022, there were 2.8 million nonfatal workplace injuries and illnesses reported by private employers. Many of these incidents could be prevented by following proper safety protocols and adhering to exposure limits for hazardous chemical substances and physical agents.

What is a Permissible Exposure Limit?

A Permissible Exposure Limit (PEL) is the maximum amount or concentration of a chemical that a worker can be exposed to under OSHA regulations. These limits are typically measured in parts per million (ppm) or milligrams per cubic meter (mg/m³) and are expressed as:

    • Time-Weighted Average (TWA): TWA is the average exposure to a particular substance over a specified period, usually an 8-hour workday or a 40-hour workweek. It is calculated by averaging the occupational exposure levels at different times throughout the work period.
    • Short-Term Exposure Limit (STEL): STEL refers to the maximum concentration of a substance to which workers can be exposed for a short period, typically 15-30 minutes of maximum exposure, without suffering adverse effects. Unlike TWA, STEL addresses short-term, high-intensity exposure that could cause immediate or acute health effects.

What is the Importance of a Permissible Exposure Limit (PEL)?

PELs are crucial for safeguarding workers' health by limiting their exposure to harmful chemical substances. Setting PELs help:

    • Protect worker health: By limiting occupational exposure to hazardous materials and physical agents, PELs help prevent a wide range of health problems, from respiratory issues to skin conditions and even cancer.
    • Establish a benchmark for compliance: PELs provide employers with a clear guideline for maintaining a safe work environment.
    • Facilitate enforcement: OSHA inspectors use PELs to evaluate workplace conditions and identify potential hazards.

PEL vs. TLV vs. REL

Permissible Exposure Limits (PELs) are regulatory limits set by the OSHA to protect workers from the harmful effects of exposure to hazardous substances. These limits are enforceable by law, meaning employers are legally required to comply with them. PELs are typically expressed as a Time-Weighted Average (TWA) over an 8-hour workday, but can also include Short-Term Exposure Limits (STEL) and Ceiling limits. They are based on scientific data, as well as considerations of feasibility and economic impact at the time they were established.

Threshold Limit Values (TLVs), on the other hand, are guidelines developed by the American Conference of Governmental Industrial Hygienists (ACGIH). While not legally enforceable, the Threshold Limit Value is widely respected and used as reference points across various industries. They are also expressed as TWA, STEL, and Ceiling limits. Unlike PELs, TLVs focus solely on health factors and are derived from the latest toxicological and epidemiological data, without taking economic or technical feasibility into account. This means TLVs often provide a higher level of protection for workers.

Recommended Exposure Limits (RELs) are guidelines issued by the National Institute for Occupational Safety and Health (NIOSH). Similar to Threshold Limit Values (TLVs), RELs are not legally enforceable but are used to inform OSHA standards and industry practices. RELs are based on rigorous scientific research and aim to prevent adverse health effects from workplace exposures. They prioritize worker health protection without considering economic impact and are expressed in terms of TWA, STEL, and Ceiling limits.

The key differences among these limits lie in their regulatory status, basis for limits, and frequency of updates. PELs are legally binding and consider both health and economic factors. TLVs and RELs, however, are advisory limits that focus exclusively on health data and are regularly updated to reflect new scientific findings. Despite being advisory, TLVs and RELs are crucial for industries aiming to implement more stringent safety measures than those mandated by PELs.


Common Hazardous Materials and their PELs

Understanding the Permissible Exposure Limits (PELs) for common hazardous materials is crucial for maintaining occupational safety. PELs define the maximum amount of a hazardous substance that workers can be exposed to without adverse health effects.

Hazardous Material  CAS Number PEL (TWA) Health Effects
Benzene 71-43-2 1 ppm Leukemia, bone marrow depression
Asbestos 1332-21-4 0.1 fiber/cc Lung cancer, asbestosis, mesothelioma
Lead 7439-92-1 50 µg/m³ Anemia, kidney damage, neurological effects
Formaldehyde 50-00-0 0.75 ppm Respiratory issues, cancer
Silica, Crystalline 14808-60-7 50 µg/m³ Silicosis, lung cancer


For more information on PELs of various chemicals, you can check out the Permissible Exposure Limits annotated tables by OSHA. The Permissible Exposure Limits annotated tables by OSHA provide comprehensive information on the exposure limits for various hazardous substances in the workplace. These tables are essential resources for employers, safety professionals, and workers to ensure occupational safety and health.


Is OSHA PEL Outdated?

Many of the Permissible Exposure Limits (PELs) set by the Occupational Safety and Health Administration (OSHA) have not been updated since their initial establishment in the 1970s. As a result, some of these standards are considered outdated, not reflecting the latest scientific understanding of the occupational safety and health risks associated with exposure to various hazardous substances. Despite this, OSHA continues to enforce these limits, leading to criticism from safety advocates who argue that current PELs do not adequately protect workers.

Recognizing the limitations of existing OSHA PELs, many large industrial organizations have felt obligated to supplement them with alternative occupational exposure limits. Additionally, OSHA's Hazard Communication Standard (1910.1200 Appendix D) mandates that safety data sheets list not only the relevant OSHA PEL but also the ACGIH TLV and any other alternative occupational exposure limits or limit used or recommended by the chemical manufacturer, importer, or employer preparing the safety data sheet.

Cal/OSHA Permissible Exposure Limits (PELs)

California Division of Occupational Safety and Health (Cal/OSHA) sets its own PELs, which are often more stringent than federal OSHA limits. These state-level regulations are designed to provide enhanced protection for workers in California, taking into account newer scientific data and health risk assessments. Cal/OSHA’s proactive approach ensures that workers are safeguarded against exposures that may not be adequately covered by federal standards.

NIOSH and Recommended Exposure Limits (RELs)

National Institute for Occupational Safety and Health (NIOSH) RELs are federal recommendations designed to protect worker health, established by evaluating medical, biological, engineering, chemical, and trade information. These recommendations are transmitted to OSHA for developing legally enforceable standards. NIOSH's mandate is to recommend standards that ensure workplace safety and health based on comprehensive hazard evaluation.


The American Conference of Governmental Industrial Hygienists (ACGIH) provides health-based guidelines, including the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs), to help control occupational health hazards. TLVs represent safe airborne concentrations of chemicals, while BEIs assess chemical levels in biological media. Both are based solely on health factors, without considering economic or technical feasibility. ACGIH emphasizes that these guidelines should not be adopted as standards without comprehensive risk management analysis.


Employer Responsibilities to Comply with PEL

engineering controls help manage exposure limits

OSHA enforces Permissible Exposure Limits, and employers have a legal obligation to comply. Here are some key steps employers must take:

    • Implement Controls: Employers must implement engineering controls to minimize worker exposure to hazardous substances. This includes installing ventilation systems, using less harmful materials, and altering work processes to reduce exposure.
    • Provide PPE: Employers are required to provide appropriate personal protective equipment (PPE) such as respirators, gloves, and safety glasses. PPE acts as a barrier between the worker and hazardous substances, ensuring their safety during operations.
    • Train Employees: Training employees on hazard recognition, safe work practices, and the proper use of PPE is essential. This ensures that workers are aware of potential risks and know how to protect themselves effectively.
    • Monitor Exposure: Employers must regularly monitor exposure levels through air sampling and personal monitoring devices. This helps identify areas of concern and ensures that exposure levels remain within permissible limits.
    • Maintain Records: Employers are required to maintain detailed records of worker exposure and medical evaluations. These records help track exposure over time and provide valuable information for health assessments.
    • Report to OSHA: Employers must report any violations and accidents involving hazardous substances to OSHA. This transparency ensures that proper investigations can be conducted and corrective actions can be implemented.


Employee Rights to Information, Monitoring, and Evaluations

Employees have the right to a safe work environment and access to information regarding potential hazards. Industrial hygiene supports these rights by providing the necessary scientific and practical framework to manage and mitigate occupational exposure risks. Here's a breakdown of some key employee rights:

    • Know Hazards: Employees have the right to know about workplace hazards and the associated Permissible Exposure Limits (PELs). This information helps them understand the risks and take appropriate precautions.
    • Access Safety Data Sheets: Employees can access Safety Data Sheets (SDS) for hazardous materials used in their workplace. SDS provides detailed information on the properties of each substance, including health effects and safety measures.
    • Request Monitoring: Employees have the right to request exposure monitoring to ensure that their work environment is safe. If monitoring results indicate high exposure levels, corrective actions must be taken to reduce risks.
    • Receive Evaluations: Employees are entitled to receive medical evaluations related to potential exposures. These evaluations help detect any adverse health effects early and ensure timely medical intervention.
    • File Complaints: Employees can file complaints with OSHA if they believe that PELs are not being met or if their safety is compromised. Filing a complaint initiates an investigation to address and resolve occupational safety concerns.



What does PEL mean?

PEL stands for Permissible Exposure Limit, which is the maximum amount of a substance a worker can be exposed to over a workday.

What is the difference between PEL and STEL?

PEL is a limit for an 8-hour workday, while STEL (Short-Term Exposure Limit) is the maximum exposure allowed over a short period, typically 15 minutes.

What is the permissible exposure limit for respirable crystalline silica?

The PEL for respirable crystalline silica is 50 µg/m³ as an 8-hour TWA.

What is the permissible exposure limit for asbestos?

The PEL for asbestos is 0.1 fiber per cubic centimeter of air (0.1 f/cc) as an 8-hour TWA.

Are OSHA PELs legally enforceable?

Yes, OSHA PELs are legally enforceable and must be complied with by employers.

What is the OSHA permissible CO2 level?

The OSHA PEL for carbon dioxide (CO2) is 5,000 ppm as an 8-hour TWA.


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The material provided in this article is for general information purposes only. It is not intended to replace professional/legal advice or substitute government regulations, industry standards, or other requirements specific to any business/activity. While we made sure to provide accurate and reliable information, we make no representation that the details or sources are up-to-date, complete or remain available. Readers should consult with an industrial safety expert, qualified professional, or attorney for any specific concerns and questions.


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Author: Herbert Post

Born in the Philadelphia area and raised in Houston by a family who was predominately employed in heavy manufacturing. Herb took a liking to factory processes and later safety compliance where he has spent the last 13 years facilitating best practices and teaching updated regulations. He is married with two children and a St Bernard named Jose. Herb is a self-described compliance geek. When he isn’t studying safety reports and regulatory interpretations he enjoys racquetball and watching his favorite football team, the Dallas Cowboys.