Acceptable Exposure Limits …extrapolation of toxicological data to recommendations for limits for occupational exposures

Development of Exposure Standards ACGIH ANSI NIOSH OSHA

Threshold Limit Values (TLV’s) Published by ACGIH A time-weighted average (TWA) concentration under which most people can work consistently for 8 hours a day, day after day, with no harmful effects.

3 Categories of TLV’s TLV-TWA TLV-STEL TLV-C

Biological Exposure Indices (BEI) Adopted by ACGHI Based on urine, blood, or expired air samples

TWA vs. Ceiling Excursions above the TLV-TWA are permitted provided they are compensated by excursions below the TLV-TWA Amount permitted to be exceeded depends upon: –Nature of contaminants –Whether acute poisonings are produced from high concentrations, even for short periods –Whether the effects are cumulative –The frequency with which high concentrations occur –The duration of the high concentration

Let’s examine some TLV’s… Some TLV notations… SEN Skin PNOS Simple asphyxiant BEI A1, A2, A3, A4, A5

Notice of Intent Notice of intended changes –Proposed actions of TLV’s for forthcoming year –Provides opportunity for comment and solicits suggestions

TLV’s- What are they? ACGIH copyrighted For occupational exposures Refer to airborne concentration Apply to NEARLY all workers Reviewed/revised regularly Guidelines for the pros

TLV’s -What they are not Common denominator for safety Proof of injury Air pollution values Permanent Legal standards To be used by persons unfamiliar with them

Permissible Exposure Limits (PELs) Published by OSHA Enforceable 8 hour average airborne concentration to which workers can be exposed to without suffering any adverse health effects Immediately Dangerous to Life or Health (IDLH) Action Level

Calculating TWA TWA= C a T a + C b T b + … C n T n 8 Where: T a – time of 1 st exposure period during the shift C a – concentration of contaminant in period “a” T b – another time period during the shift C b - the concentration during period “b” T n – the n th or final time period in a shift C n – the concentration during period “n”

Units Normally: PPM – gases and vapors mg/m 3 – particulates/aerosols mppcf- particulates fibers/cc - asbestos

Where do we gather data? Material Safety Data Sheets SOPs Policies and procedures

OSHA Toxic and Hazardous Substances – Subpart Z – 1450 Table Z-1 Limits for Air Contaminants Table Z-2 Table Z-3

Basic Recognition Procedures What is the process? What raw materials are used? What materials are added in the process? What equipment is involved? What is the cycle of operations? What operational procedures are used? Is there a written procedure for the safe handling and storage of materials?

Basic Recognition Procedures (cont.) What about dust control, cleanup after spills, and waste disposal? Are the ventilating and exhaust systems adequate? Does the facility layout minimize exposure? Is the facility well-equipped with safety appliances such as showers, masks, respirators? Are SOPs outlined and enforced? Is a complete Hazard Communication Program in effect?

What next? ID chemicals and contaminants in the process For each contaminant, find the OSHA PEL, or other safe exposure guideline Determine the actual level of exposure Determine # of employees exposed and length of exposure Calculate daily average and peak exposures Compare calculated exposures with OSHA Standards or other toxicological data

Group activity…