HSE Occupational Health and Hygiene 2 — Questions and Answers
Question 1: What is the primary purpose of Threshold Limit Values (TLVs) established by ACGIH?
- To set legal enforcement limits for OSHA inspectors
- To define airborne concentrations of substances to which workers may be repeatedly exposed without adverse health effects (Correct answer)
- To establish the minimum exposure needed to trigger medical surveillance
- To determine acceptable skin absorption rates for all chemicals
Correct answer: To define airborne concentrations of substances to which workers may be repeatedly exposed without adverse health effects
TLVs represent airborne concentrations of chemical substances below which nearly all workers may be repeatedly exposed day after day without adverse health effects.
Question 2: Biological monitoring differs from air monitoring in occupational hygiene because it:
- Measures contaminants only in the breathing zone
- Assesses the actual absorbed dose in the worker's body (Correct answer)
- Only applies to physical hazards like noise
- Replaces the need for engineering controls
Correct answer: Assesses the actual absorbed dose in the worker's body
Biological monitoring measures the worker's internal exposure by analyzing blood, urine, or exhaled air, reflecting actual absorbed dose from all routes including skin and ingestion.
Question 3: Which type of ventilation is most appropriate for controlling a highly toxic chemical released at a localized point source?
- General dilution ventilation
- Local exhaust ventilation (LEV) (Correct answer)
- Supply-only mechanical ventilation
- Natural convection ventilation
Correct answer: Local exhaust ventilation (LEV)
Local exhaust ventilation captures contaminants at the source before they disperse into the workroom air, making it most effective for highly toxic point-source releases.
Question 4: A worker is exposed to two chemical solvents simultaneously. Solvent A is at 60% of its TLV and Solvent B is at 50% of its TLV. What is the combined exposure index, and is it acceptable?
- 0.55 — acceptable
- 1.10 — not acceptable (Correct answer)
- 0.60 — acceptable
- 1.10 — acceptable because each is below its own TLV
Correct answer: 1.10 — not acceptable
For chemicals with similar effects, the mixture formula sums the fractions (0.60 + 0.50 = 1.10), which exceeds 1.0 and is therefore not acceptable.
Question 5: What does the term 'permissible exposure limit' (PEL) refer to in the context of OSHA regulations?
- A voluntary guideline recommended by NIOSH
- A legally enforceable maximum airborne concentration of a substance (Correct answer)
- A short-term exposure limit applied only during peak tasks
- The lowest concentration detectable by industrial hygiene instruments
Correct answer: A legally enforceable maximum airborne concentration of a substance
OSHA PELs are legally enforceable maximum concentrations of hazardous substances in workplace air, codified in 29 CFR 1910.1000.
Question 6: In the hierarchy of controls for occupational health hazards, which control is considered most effective?
- Administrative controls such as job rotation
- Personal protective equipment
- Elimination of the hazard at the source (Correct answer)
- Warning signs and labels
Correct answer: Elimination of the hazard at the source
Elimination removes the hazard entirely and is the most effective control, sitting at the top of NIOSH's hierarchy of controls.
Question 7: Work-related musculoskeletal disorders (WMSDs) are primarily caused by which combination of ergonomic risk factors?
- Extreme temperatures, ultraviolet radiation, and shift work
- Force, repetition, awkward postures, contact stress, and vibration (Correct answer)
- Noise exposure, chemical absorption, and poor lighting
- High altitude, confined spaces, and excessive workload
Correct answer: Force, repetition, awkward postures, contact stress, and vibration
WMSDs are driven by ergonomic risk factors including forceful exertions, repetitive motions, awkward postures, contact stress, and hand-arm or whole-body vibration.
HSE Occupational Health and Hygiene 2
What is the primary purpose of Threshold Limit Values (TLVs) established by ACGIH?