CIH General Practice 4 — Questions and Answers
Question 1: A manufacturing plant uses methylene chloride. Which metabolic conversion makes this solvent particularly hazardous beyond its direct toxic effects?
- It is metabolized to formaldehyde in the liver
- It is endogenously converted to carbon monoxide, elevating carboxyhemoglobin (Correct answer)
- It undergoes reductive dehalogenation to vinyl chloride
- It is converted to phosgene upon hepatic oxidation
Correct answer: It is endogenously converted to carbon monoxide, elevating carboxyhemoglobin
Methylene chloride is metabolized via the mixed-function oxidase pathway to carbon monoxide, which binds hemoglobin and impairs oxygen delivery.
Question 2: Which factor is LEAST relevant when selecting an air-purifying respirator cartridge for a volatile organic compound?
- The chemical's service life as determined by end-of-service-life indicators or models
- The chemical's vapor pressure and concentration in the workplace air
- The assigned protection factor of the facepiece style
- The color of the worker's hair and skin (Correct answer)
Correct answer: The color of the worker's hair and skin
Cartridge selection depends on chemical properties, concentration, service life, and APF—not on the wearer's physical appearance.
Question 3: A CIH is asked to evaluate whole-body vibration (WBV) exposure for forklift operators. The primary health outcome of concern is:
- Raynaud's phenomenon (white finger syndrome)
- Low back pain and musculoskeletal disorders (Correct answer)
- Carpal tunnel syndrome
- Noise-induced hearing loss from engine vibration
Correct answer: Low back pain and musculoskeletal disorders
Whole-body vibration transmitted through the seat and floor is strongly associated with low back pain and degenerative spine disorders in vehicle operators.
Question 4: When calculating the combined exposure index for a mixture of chemicals with additive effects, which formula applies?
- Multiply each C/TLV ratio and take the product
- Sum each C/TLV ratio: ΣCn/TLVn (Correct answer)
- Use the largest individual C/TLV ratio only
- Average all C/TLV ratios across components
Correct answer: Sum each C/TLV ratio: ΣCn/TLVn
For additively acting mixtures, ACGIH recommends summing the ratios C1/TLV1 + C2/TLV2 + ... and the mixture exceeds the TLV if the sum exceeds 1.
Question 5: Under OSHA's Process Safety Management (PSM) standard, which element specifically requires a team-based structured hazard identification technique?
- Management of Change (MOC)
- Process Hazard Analysis (PHA) (Correct answer)
- Pre-Startup Safety Review (PSSR)
- Emergency Planning and Response
Correct answer: Process Hazard Analysis (PHA)
OSHA PSM (29 CFR 1910.119) requires a Process Hazard Analysis conducted by a multidisciplinary team using methods such as HAZOP, What-If, or FMEA.
Question 6: The biological exposure index (BEI) for a chemical differs from the TLV because the BEI:
- Applies only to chemicals with OSHA PELs
- Reflects internal body burden rather than airborne concentration (Correct answer)
- Is always more stringent than the corresponding TLV
- Measures environmental contamination on work surfaces
Correct answer: Reflects internal body burden rather than airborne concentration
BEIs measure biomarkers in blood, urine, or exhaled air that reflect the absorbed dose regardless of the route of entry, whereas TLVs are airborne concentration limits.
Question 7: In an industrial hygiene program, what is the main purpose of a written exposure assessment strategy prior to sampling?
- To satisfy OSHA's requirement for a written IH plan under 29 CFR 1910.1000
- To define similar exposure groups, select representative workers, and choose appropriate sampling strategies before resources are spent (Correct answer)
- To provide legal protection for the company in litigation
- To identify which workers refuse to wear personal protective equipment
Correct answer: To define similar exposure groups, select representative workers, and choose appropriate sampling strategies before resources are spent
A written exposure assessment strategy defines similar exposure groups and guides efficient, statistically defensible sampling before fieldwork begins.
CIH General Practice 4
A manufacturing plant uses methylene chloride.
Which metabolic conversion makes this solvent particularly hazardous beyond its direct toxic effects?