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Appendix D - Training Program

Occupational Exposure Limits

Objectives/Samples of Behavior:

  1. Explain what OELs are and their possible sources.

  2. Distinguish among TWAs, STELs, ceiling limits, skin notations, and IDLH limits.

  3. Identify what to do when OELs are exceeded.

A.  Sources

  1. Air Force Occupation Safety and Health (AFOSH) Standard 48-8 OELs

  1. Limits enforceable

  2. Appendices for specific substances - lead, hydrazine, etc.

  1. Occupation Safety & Health Administration (OSHA) Permissible Exposure Limits (PELs)

  1. Found in 29 CFR 1910 (Subpart Z)

  2. Legal lijmits for restricting worker exposures

  1. American Conference of Governmental Industrial Hygieneists (ACGIH) Threshold Limit Values (TLVs)

  1. ACGIH TLV booklet

  2. Instrial hygiene guidelines

  3. Limits enforceable by the Air Force

  1. National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limits (REL)

  1. NIOSH Pocket Guide

  2. Usually not enforceable

  3. Ultraconservative in some cases

B.  Definitions and Restrictions

  1. Air Force occupational exposure limits

OELS are the most stringent of:

AFOSH Standard values

OSHA PELs

ACGIH TLVs

NIOSH RELs

  1. Published exposure limits (only according to 29 CFR 1910.120)

If no OSHA PEL exists and the operation is covered under HAZWOPER, the published exposure level is the NIOSH REL.

If no NIOSH REL, the published exposure limit is the ACGIH TLV

  1. Air Force emergency exposure guidelines

  1. These are NOT occupational exposure guidelines; they are for public exposure during emergency situations

  2. These guidelines are discussed in AFOSH Standard 48-8

  3. Sources:

National Academy of Sciences (NAS) - prpeferred limits - SPEGLS / EEGLs - Short-term Public Emergency Exposure Guidelines and Emergency Exposure Guidelines

American Industrial Hygiene Association - when no SPEGL / EEGL available - ERPG - Emergency Response Planning Guidelines

Last choice for emergency evacuation of personnel: ACGIH TLVs and OSHA PELs

  1. OEL restrictions

OELs do not apply to evaluations of:

Community air pollution

Continuous exposures

Hypersensitive personnel

Protection of the fetus

Protection of mother's milk

  1. ACGIH TLV definition:  Airborne concentration of substances representing conditions under which it is believed that nearly all workers may be exposed day after day without adverse effects.

  2. ACGIH TLV restrictions:

  1. Only covers the majority of workers

  2. Cannot determine safe vs unsafe conditions

  3. Does not prove or disprove disease

  4. Does not establish relative index of toxicity

  5. Adverse effects include health impairment, irritation, nuisance, narcosis and stress

  6. Not for working conditions different from those in the United States

  1. IDLH - immediately dangerous to life or health

  1. NIOSH definition:  the maximum concentration from which, in the event of respiratory protection failure, one could escape without experiencing any escape-impairing (e.g. severe eye irritation) or irreversible health effects.

  2. OSHA definition:  any condition that poses an immediate or delayed threat to life or health that would cause irreversible adverse health effects or interfere with an individual's ability to escape.

  3. IDLH concentrations are found in NIOSH pocket guide

  4. Only purpose is respirator selection

  5. MUST wear SCBA to ENTER an IDLH atmosphere

  1. OEL concentrations - units of measure

  1. Gases and vapors.  There is a conversion factor which may be used to convert mg/m3 to ppm.  Either unit may be used.

Milligrams per cubic meter (mg/m3)

Parts per million (ppm)

  1. Aerosols

Milligrams per cubic meter (mg/m3)

Fibers per cubic centimeter (asbestos only at this point)

C.  Types of OELs

  1. Time-weighted average (8-hr OEL-TWA & TLV-TWA)

  1. Based on an 8 hr work day, 40 hr week

  2. Usually based on chronic exposures

  3. Calculate an average worker's daily exposures using the equation:

TWA = (C1T1 + C2T2 + ... CnTn) / (8 hours)

  1. Short term exposure limit (OEL-STEL & TLV-STEL)

  1. Based on acute effects

  2. ACGIH/AFOSH Std definition:  a 15 minute time-weighted average exposure which must not be exceeded during the workday

  3. Exposures above the TLV-TWA up to the STEL should not be longer than 15 minutes and should not occur more than 4 times per day

  4. There should be at least 60 minutes bnetween successive exposures in this range

  5. The 8-hr TWA must not be exceeded

  1. Ceiling limit (OEL-C & TLV-C)

  1. For substances which are fast-acting - often for irritants

  2. A concentration which must be exceeded, even instantaneously, at any time during the workday

  3. OSHA ceilings are different - "C" notation vs "acceptable ceiling concentration"

  1. Excursion limits

  1. For substances with OEL-TWA values but no STEL or ceiling

  2. Excursions at levels up to three times the OEL-TWA are allowed for no more than a total of 30 minutes per workday

  3. Levels should never exceed five times the OEL-TWA

  4. The daily OEL-TWZ must not be exceeded

  1. "Skin" notation

  1. Chemical vapor or liquid may be absorbed through intact skin

  2. Contributes to the overall dose

  3. Inhalation + skin absorption = greater dose than air sampling indicates

  4. OELs based ONLY on inhalation

  5. Therefore, OEL may be invalidated for a chemical with a skin notation

D.  What to do when OELs are exceeded - do something to reduce exposure below the OEL

  1. Substitution best but not always practical

  2. Recommend controls to lower exposure

  1. Engineering controls

  2. Administrative controls / work practices

  3. PPE (respiratory protection)

E.  Only trained / knowledgeable / experienced personnel should interpret air sampling results

  1. BEE personnel, industrial hygienists & technicians, etc.

  2. For contractors, this should be done by industrial hygienists