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Permissible Exposure Limits (PELs) are regulations that establish the acceptable amount or concentration of a substance in the air in the workplace. They are intended to protect workers from adverse health effects related to hazardous chemical exposure. Of the thousands of chemicals used in workplaces, OSHA has PELs for less than 500. Many of the PELs have not been updated since 1971, and current scientific data suggests that, in many instances, the outdated PELs are not sufficiently protective of worker health.
Industrial experience, new developments in technology, and scientific data clearly indicate that in many instances these adopted limits are not sufficiently protective of worker health. This has been demonstrated by the reduction in allowable exposure limits recommended by many technical, professional, industrial, and government organizations, both inside and outside the United States. Many large industrial organizations have felt obligated to supplement the existing OSHA PELs with their own internal corporate guidelines. OSHA’s Hazard Communication standard (1910.1200 Appendix D) requires that safety data sheets list not only the relevant OSHA PEL but also the ACGIH® TLV® and any other exposure limit used or recommended by the chemical manufacturer, importer, or employer preparing the safety data sheet.
To provide employers, workers, and other interested parties with a list of alternate occupational exposure limits that may serve to better protect workers, OSHA has annotated the existing Z-Tables with other selected occupational exposure limits. OSHA has chosen to present a side-by-side table with the Cal/OSHA PELs, the NIOSH Recommended Exposure Limits (RELs) and the ACGIH® TLVs®. The tables list air concentration limits, but do not include notations for skin absorption or sensitization.
OSHA’s mandatory PELs in the Z-Tables remain in effect. However, OSHA recommends that employers consider using the alternative occupational exposure limits because it believes that exposures above some of these alternative occupational exposure limits may be hazardous to workers, even when the exposure levels are in compliance with the relevant PELs.
Scope
OSHA enforces hundreds of permissible exposure limits (PELs) for toxic air contaminants found in U.S. workplaces. These PELs set enforceable limits on the magnitude and duration of employee exposure to each contaminant. The amount of exposure permitted by a given PEL depends on the toxicity and other characteristics of the particular substance. Two different types of measurement are used for PEL determination. The concentration of gases and liquids in the air is measured in parts per million (ppm). Solids and liquids in the form of mists, dusts, or fumes are measured in milligrams per cubic meter (mg/m3).
Subpart Z, the largest subpart under 1910, contains 1910.1000Air Contaminants. Here you will find the Z tables, Z-1, Z-2, and Z-3. These tables provide the exposure limits for many substances found in the workplace, expressed in permissible exposure limits (PELs).
Regulatory citations
- 29 CFR 1910.1000 — Air Contaminants
Key definitions
- Permissible exposure limit (PEL): The legal limit for maximum concentration of any chemical in the air to which a worker may be exposed continuously for eight hours without any danger to health and safety.
- Threshold limit value (TLV): The level to which a worker can be exposed day after day for a working lifetime without adverse effects. TLVs are guidelines developed by ACGIH®.
Summary of requirements
Air Contaminants contains the Z tables: Z-1, Z-2, and Z-3. These tables provide the exposure limits for many substances found in the workplace, expressed in permissible exposure limits (PELs), and outline employers’ responsibilities.