Occupational Exposure Limits (OELs)

Occupational Exposure Limits (OELs)

• OELs are the maximum allowable concentrations of hazardous substances in the workplace.
• Workers can be exposed to these substances daily without adverse effects.
• PEL (Permissible Exposure Limit): OSHA mandated standard.
• TLV (Threshold Limit Value): ACGIH (American Conference of Governmental Industrial Hygienists)- recommended standard.
• REL (Recommended Exposure Limit): NIOSH (National Institute for Occupational Safety and Health)- recommended standard.

Types of OELs

• TLV-TWA (Time-Weighted Average): Average exposure over an 8-hour workday, 40-hour workweek.
• TLV-STEL (Short-Term Exposure Limit): 15-minute exposure, maximum of four times per day with at least one hour between exposures.
• TLV-Ceiling: Exposure should never exceed this limit for even a moment.

Hazardous Substance Examples: Hydrogen Sulfide (H2S)

• TLV-TWA- 1 ppm
• TLV-STEL- 5 ppm
• TLV Ceiling- 20 ppm
• IDLH (Immediately Dangerous to Life and Health) for H2S is 100 ppm

Units

• PPM (Parts Per Million) is used to measure chemical concentration.

Self-Contained Breathing Apparatus (SCBA)

• SCBA is used to supply breathable air in hazardous situations.
• Types include:
  • Positive Pressure: Pressure inside the hood is higher than outside.
  • Negative Pressure: Pressure inside the hood is lower than outside.

Other Topics

• Open-type SCBA: Does not process exhaled air.
• Closed-type SCBA: Processes and reuses exhaled air.
• Airline Breathing Apparatus: Used for longer work durations.
• Maximum hose line for air line BA: 300 ft (90 meters) maximum.
• Fit Testing: Qualitative (subjective) and quantitative (numerical).
  • Qualitative uses user's sense of smell.
  • Quantitative uses instruments to measure leaks.

Vibration

• HAVS (Hand-Arm Vibration Syndrome): Symptoms include white fingers, blanching of fingers, numbness.
• WBVS (Whole Body Vibration Syndrome): Affects the spinal cord (flight attendants).
• Raynaud's Phenomenon: Reduced blood flow due to vibration.

Vibration Measurement

• Accelerometer or vibrometer.

Personal Protective Equipment (PPE)

• Levels of protection are categorized as A, B, C, and D.
• Different combinations of respirators (SCBA and Chemical hoods) and garments (chemical-resistant clothing) are necessary to comply with each level.

Cumulative Trauma Disorders (CTDs)

• Long-term musculoskeletal injuries from repetitive work.
• Examples include: Carpal Tunnel Syndrome, WRULD (Work-related upper limb disorders), and Tenosynovitis.
• Ergonomics involves designing workplaces and products to fit users anthropometric dimensions and abilities, taking 95% of the population into consideration.

Heat Stress

• Hypothermia (low temperature), heat exhaustion, heat rash, heat stroke, heat syncope, cold burns, and chill blains.
• WBGT (Wet Bulb Globe Temperature): Measure of environmental factors affecting deep body temperature.
• NIOSH Lifting Index: Measure to determine if lifting scenario is appropriate for a particular body build and scenario, and the weight. A low index means it is suitable for lifting.
• Chemical effects include:
  • Additive effect: the combined effect of multiple chemicals is equal to the sum of their individual effects.
  • Antagonistic effect: the combined effect is less than the sum of their individual effects
  • Potentiation effect: one chemical increases the toxic effect of another.
  • Synergistic effect: the combined effect is greater than the sum of individual effects.