CIH General Practice 5 — Questions and Answers
Question 1: A health hazard evaluation finds that a worker's 8-hour TWA benzene exposure is 0.4 ppm. OSHA's PEL for benzene is 1 ppm and the action level is 0.5 ppm. What is the appropriate next step?
- No action required; exposure is below both the action level and PEL (Correct answer)
- Enroll the worker in medical surveillance because the action level is exceeded
- Issue respiratory protection immediately as the exposure exceeds the action level
- Report the exposure to OSHA as an imminent danger
Correct answer: No action required; exposure is below both the action level and PEL
At 0.4 ppm, the exposure is below OSHA's benzene action level of 0.5 ppm, so no additional programmatic requirements are triggered.
Question 2: Which type of radiation is most effectively shielded by a thin sheet of paper or the dead outer layer of skin?
- Beta particles
- Gamma rays
- Alpha particles (Correct answer)
- Neutrons
Correct answer: Alpha particles
Alpha particles have very low penetrating power and are stopped by a sheet of paper, a few centimeters of air, or the outer dead layer of skin.
Question 3: When evaluating heat stress, the Wet Bulb Globe Temperature (WBGT) index incorporates which three environmental parameters?
- Dry-bulb temperature, dew point, and wind speed
- Natural wet-bulb temperature, globe temperature, and dry-bulb temperature (Correct answer)
- Black globe temperature, relative humidity, and barometric pressure
- Effective temperature, heat index, and wind chill factor
Correct answer: Natural wet-bulb temperature, globe temperature, and dry-bulb temperature
WBGT = 0.7×NWB + 0.2×GT + 0.1×DBT outdoors (or 0.7×NWB + 0.3×GT indoors), combining natural wet-bulb, globe, and dry-bulb temperatures.
Question 4: A CIH reviewing an MSDS/SDS notices a chemical has a flash point of 28°C (82°F). Under NFPA and OSHA definitions, this chemical is classified as:
- Combustible liquid (Class II)
- Flammable liquid (Class IB) (Correct answer)
- Non-flammable liquid
- Oxidizer requiring special storage
Correct answer: Flammable liquid (Class IB)
A liquid with a flash point below 37.8°C (100°F) is classified as a flammable liquid; a flash point between 22.8–37.8°C places it in Class IB under NFPA 30.
Question 5: In ergonomics, the NIOSH Lifting Equation produces a Recommended Weight Limit (RWL). A Lifting Index (LI) greater than 1.0 indicates:
- The task is perfectly safe for all workers
- The lift exceeds the RWL and poses an increased risk of low back injury for most workers (Correct answer)
- Workers should immediately stop all lifting tasks
- The task requires only a one-time engineering control
Correct answer: The lift exceeds the RWL and poses an increased risk of low back injury for most workers
An LI > 1.0 means the actual weight lifted exceeds the RWL calculated for that task, indicating that most workers performing that lift are at elevated risk of low back injury.
Question 6: Which OSHA standard requires employers to develop a written respiratory protection program when respirators are necessary?
- 29 CFR 1910.132 (Personal Protective Equipment)
- 29 CFR 1910.134 (Respiratory Protection) (Correct answer)
- 29 CFR 1910.1000 (Air Contaminants)
- 29 CFR 1910.120 (HAZWOPER)
Correct answer: 29 CFR 1910.134 (Respiratory Protection)
29 CFR 1910.134 is OSHA's Respiratory Protection standard and specifically mandates a written program covering selection, medical evaluation, fit testing, and training.
Question 7: An industrial hygienist uses a direct-reading photoionization detector (PID) to screen for VOCs. Which gas is used to calibrate most PIDs to ensure accuracy?
- Hexane
- Isobutylene (Correct answer)
- Toluene
- Methane
Correct answer: Isobutylene
Isobutylene (isobutylene at 100 ppm) is the most common calibration gas for PIDs because it has a stable, well-characterized ionization response across instruments.
CIH General Practice 5
A health hazard evaluation finds that a worker's 8-hour TWA benzene exposure is 0.4 ppm.
OSHA's PEL for benzene is 1 ppm and the action level is 0.5 ppm.
What is the appropriate next step?