CIH General Practice 2 — Questions and Answers
Question 1: Which sampling method is most appropriate when a worker's exposure varies significantly throughout the shift?
- Grab sampling at peak exposure times only
- Full-period consecutive sampling (Correct answer)
- Spot sampling averaged over 8 hours
- Passive dosimeter worn for 15 minutes
Correct answer: Full-period consecutive sampling
Full-period consecutive sampling captures the entire shift variability and provides the most representative TWA exposure estimate.
Question 2: The ACGIH TLV-STEL is defined as a concentration that should not be exceeded for more than how many minutes at a time?
- 5 minutes
- 10 minutes
- 15 minutes (Correct answer)
- 30 minutes
Correct answer: 15 minutes
The ACGIH TLV-STEL is a 15-minute TWA concentration that should not be exceeded at any time during the workday.
Question 3: A noise survey reveals a worker is exposed to 95 dBA for 4 hours and 90 dBA for 4 hours. Using OSHA's permissible noise formula, what is the dose?
- 75%
- 100%
- 125% (Correct answer)
- 150%
Correct answer: 125%
At 95 dBA the limit is 4 hours (4/4=1.0) and at 90 dBA the limit is 8 hours (4/8=0.5); combined dose = 1.0 + 0.5 = 1.5 = 150%.
Question 4: Which administrative control is most effective for reducing cumulative chemical exposure when engineering controls are not feasible?
- Increasing ventilation fan speed
- Job rotation among workers (Correct answer)
- Posting warning signs in work areas
- Providing quarterly medical exams
Correct answer: Job rotation among workers
Job rotation distributes exposure among multiple workers, reducing any single worker's cumulative dose when source elimination is not possible.
Question 5: What does a real-time aerosol monitor measure that a gravimetric filter method does not provide?
- Mass concentration of collected particles
- Chemical composition of the aerosol
- Continuous time-resolved concentration data (Correct answer)
- Particle size distribution by sieve analysis
Correct answer: Continuous time-resolved concentration data
Real-time aerosol monitors provide continuous, time-stamped concentration readings, allowing identification of peak exposure events during a shift.
Question 6: In industrial hygiene, the term 'action level' under OSHA standards typically represents what fraction of the PEL?
- One-quarter (25%)
- One-third (33%)
- One-half (50%) (Correct answer)
- Three-quarters (75%)
Correct answer: One-half (50%)
OSHA action levels are generally set at one-half (50%) of the PEL to trigger monitoring, medical surveillance, and training requirements.
Question 7: Which route of entry is most significant for lead exposure in a smelting operation?
- Dermal absorption through intact skin
- Ingestion of contaminated food and surfaces
- Inhalation of lead fume and dust (Correct answer)
- Eye contact with molten metal splatter
Correct answer: Inhalation of lead fume and dust
Inhalation of airborne lead fume and dust is the primary route of occupational exposure in high-temperature smelting operations.
CIH General Practice 2
Which sampling method is most appropriate when a worker's exposure varies significantly throughout the shift?