CIH Certified Industrial Hygienist (CIH) MCQ 4 — Questions and Answers
Question 1: Which dermal exposure route is most significant for organophosphate pesticide absorption in agricultural workers?
- Inhalation of spray droplets
- Dermal absorption through intact skin (Correct answer)
- Ingestion via hand-to-mouth contact
- Conjunctival absorption through eyes
Correct answer: Dermal absorption through intact skin
Dermal absorption through intact skin is the predominant route of organophosphate exposure for field workers due to large surface area contact with residues.
Question 2: The Threshold Limit Value for a mixture of chemicals with similar health effects is calculated using which approach?
- The TLV of the most toxic component applies to the mixture
- An additive formula: sum of (Ci/TLVi) must not exceed 1 (Correct answer)
- The mixture TLV equals the geometric mean of individual TLVs
- No adjustment is needed if each component is below its own TLV
Correct answer: An additive formula: sum of (Ci/TLVi) must not exceed 1
For chemicals with additive effects, the mixture formula Σ(Ci/TLVi) ≤ 1 must be satisfied to ensure the combined exposure is acceptable.
Question 3: Which instrument is most appropriate for measuring real-time concentrations of combustible gases to assess explosion risk?
- Flame ionization detector (FID)
- Catalytic bead combustible gas detector (CGI) (Correct answer)
- Photoionization detector (PID)
- Colorimetric detector tube
Correct answer: Catalytic bead combustible gas detector (CGI)
Catalytic bead combustible gas indicators (CGIs) measure % LEL in real time and are the standard tool for explosion risk assessment.
Question 4: A worker develops metal fume fever after welding on galvanized steel. The causative agent is fumes of:
- Lead oxide
- Zinc oxide (Correct answer)
- Manganese dioxide
- Iron oxide
Correct answer: Zinc oxide
Metal fume fever is most commonly caused by inhalation of freshly generated zinc oxide fumes from welding or cutting galvanized (zinc-coated) steel.
Question 5: Which control measure hierarchy level does administrative rotation of workers through high-noise areas represent?
- Elimination
- Engineering controls
- Administrative controls (Correct answer)
- Personal protective equipment
Correct answer: Administrative controls
Rotating workers to limit their time in high-noise areas is an administrative control, the third tier in the hierarchy of controls.
Question 6: The concept of 'biological half-life' in toxicology refers to:
- Time for 50% of a chemical to be excreted by the kidneys
- Time for the plasma concentration to decrease by 50% due to all elimination processes (Correct answer)
- Time for 50% of a chemical to cross the blood-brain barrier
- Time required for 50% metabolism by liver enzymes
Correct answer: Time for the plasma concentration to decrease by 50% due to all elimination processes
Biological half-life is the time required for the concentration of a substance in the body (typically plasma) to decrease by 50% through all elimination pathways.
Question 7: ACGIH classifies substances as A1, A2, A3, A4, or A5 carcinogens. Which designation means 'confirmed human carcinogen'?
- A2
- A3
- A4
- A1 (Correct answer)
Correct answer: A1
A1 is ACGIH's designation for confirmed human carcinogens, based on epidemiological evidence in humans.
CIH Certified Industrial Hygienist (CIH) MCQ 4
Which dermal exposure route is most significant for organophosphate pesticide absorption in agricultural workers?