CIH Hazards & Exposures 5 — Questions and Answers
Question 1: Which dose-response model assumes that any level of exposure to a carcinogen carries some finite risk — i.e., there is no threshold below which risk is zero?
- Linear non-threshold (LNT) model (Correct answer)
- Threshold model
- Hormesis model
- Probit model
Correct answer: Linear non-threshold (LNT) model
The linear non-threshold model assumes carcinogenic risk increases linearly from zero dose, with no safe threshold, and is commonly applied to genotoxic carcinogens.
Question 2: A laboratory worker is accidentally exposed to a nerve agent simulant that inhibits acetylcholinesterase. Which physiologic effect would be expected?
- Excessive secretions, miosis, bradycardia, and muscle fasciculations (cholinergic crisis) (Correct answer)
- Dry mouth, tachycardia, dilated pupils, and urinary retention (anticholinergic crisis)
- Hypertensive emergency with diaphoresis and palpitations
- Rapid respiratory alkalosis with tetany
Correct answer: Excessive secretions, miosis, bradycardia, and muscle fasciculations (cholinergic crisis)
Acetylcholinesterase inhibition prevents breakdown of acetylcholine, causing overstimulation of muscarinic and nicotinic receptors resulting in a cholinergic toxidrome.
Question 3: An IH is monitoring workers in a spray painting booth that uses an HVOC coating. Air sampling results show exposures are below PELs, but the IDLH for the solvent blend is 500 ppm and the highest measured concentration is 420 ppm. What action is most appropriate?
- Treat the atmosphere as IDLH and require supplied-air respirators; concentrations >10% of IDLH require SCBA or SAR (Correct answer)
- No additional action needed because concentrations are below PELs
- Provide air-purifying respirators since concentrations are below IDLH
- Conduct additional sampling for 30 days before making a control decision
Correct answer: Treat the atmosphere as IDLH and require supplied-air respirators; concentrations >10% of IDLH require SCBA or SAR
OSHA requires supplied-air respirators when concentrations are at or above 10% of the IDLH value (here 50 ppm), and when approaching IDLH, escape-only SCBAs are mandatory.
Question 4: Which occupational disease is caused by inhalation of cotton, flax, or hemp dust and is characterized by chest tightness that is worst on Monday mornings?
- Byssinosis (Correct answer)
- Silicosis
- Asbestosis
- Hypersensitivity pneumonitis
Correct answer: Byssinosis
Byssinosis ('brown lung') is caused by organic cotton dust and classically presents with Monday morning chest tightness that improves as the week progresses.
Question 5: A heat stress evaluation using the Wet Bulb Globe Temperature (WBGT) index weighs three measurements. Which component carries the highest weighting factor outdoors?
- Natural wet bulb temperature (NWB) (Correct answer)
- Globe temperature (GT)
- Dry bulb temperature (DB)
- All three are weighted equally
Correct answer: Natural wet bulb temperature (NWB)
The outdoor WBGT formula is 0.7 NWB + 0.2 GT + 0.1 DB, assigning the greatest weight (70%) to the natural wet bulb to reflect evaporative cooling's dominance.
Question 6: A confined space atmosphere reads 22% oxygen, 0 ppm CO, 0 ppm H₂S, and 8% LEL. How should entry proceed?
- Entry is permitted with continuous monitoring; the LEL reading requires awareness but is below the 10% action level (Correct answer)
- Entry is prohibited because LEL readings above 0% require SCBA
- Entry is prohibited due to elevated oxygen creating a fire hazard
- Entry is permitted with no restrictions because all readings appear normal
Correct answer: Entry is permitted with continuous monitoring; the LEL reading requires awareness but is below the 10% action level
OSHA requires control measures when LEL exceeds 10%; at 8% the space is not immediately unsafe but continuous monitoring and ventilation assessment are required before entry.
Question 7: Which metal is MOST associated with causing 'metal fume fever,' a self-limiting flu-like illness occurring within hours of overexposure?
- Zinc (Correct answer)
- Lead
- Mercury
- Chromium
Correct answer: Zinc
Zinc oxide fume generated during welding or galvanizing is the most common cause of metal fume fever, a febrile syndrome typically resolving within 24–48 hours.
CIH Hazards & Exposures 5
Which dose-response model assumes that any level of exposure to a carcinogen carries some finite risk — i.e., there is no threshold below which risk is zero?