HSE Occupational Health and Hygiene 3 — Questions and Answers
Question 1: A short-term exposure limit (STEL) is defined as the maximum concentration a worker may be exposed to for up to how long without suffering irritation, tissue damage, or narcosis?
- 15 minutes (Correct answer)
- 30 minutes
- 1 hour
- 2 hours
Correct answer: 15 minutes
A STEL is the airborne concentration to which workers can be exposed for up to 15 minutes, no more than 4 times per day, with at least 60 minutes between exposures.
Question 2: Which type of respirator provides the highest level of respiratory protection for IDLH (immediately dangerous to life or health) atmospheres?
- Air-purifying half-face respirator with P100 filters
- Powered air-purifying respirator (PAPR)
- Self-contained breathing apparatus (SCBA) in positive-pressure mode (Correct answer)
- Supplied-air respirator in demand mode
Correct answer: Self-contained breathing apparatus (SCBA) in positive-pressure mode
A positive-pressure SCBA provides the highest protection factor and is the required respirator for IDLH atmospheres because it supplies its own air supply.
Question 3: Noise-induced hearing loss (NIHL) is classified as which type of hearing loss?
- Conductive hearing loss affecting the middle ear
- Sensorineural hearing loss affecting the cochlea's hair cells (Correct answer)
- Mixed hearing loss involving both outer and inner ear
- Central hearing loss caused by auditory nerve damage
Correct answer: Sensorineural hearing loss affecting the cochlea's hair cells
NIHL is a sensorineural hearing loss caused by permanent damage to the hair cells in the cochlea from excessive sound pressure levels.
Question 4: OSHA's Hearing Conservation Amendment requires hearing protection and audiometric testing when an employee's 8-hour TWA noise exposure equals or exceeds what level?
- 80 dBA
- 85 dBA (Correct answer)
- 90 dBA
- 95 dBA
Correct answer: 85 dBA
The OSHA action level is 85 dBA as an 8-hour TWA, at which point employers must implement a hearing conservation program including audiometric testing and hearing protection.
Question 5: What is the primary health risk associated with chronic inhalation of crystalline silica dust?
- Asbestosis (pulmonary fibrosis from asbestos)
- Silicosis (irreversible fibrotic lung disease) (Correct answer)
- Byssinosis (airway obstruction from cotton dust)
- Mesothelioma (cancer of the pleural lining)
Correct answer: Silicosis (irreversible fibrotic lung disease)
Chronic inhalation of respirable crystalline silica causes silicosis, an irreversible and potentially fatal fibrotic lung disease, and also increases lung cancer risk.
Question 6: In occupational health, what does the term 'sensitizer' describe?
- A substance that immediately irritates mucous membranes on first contact
- A substance that, after repeated low-level exposure, causes the immune system to react upon subsequent exposure (Correct answer)
- A chemical that increases sensitivity to UV radiation
- An agent that lowers the TLV of co-existing substances
Correct answer: A substance that, after repeated low-level exposure, causes the immune system to react upon subsequent exposure
A sensitizer induces an allergic immune response after repeated exposure; once sensitized, a worker may react severely even to trace amounts.
Question 7: Which of the following is the correct order of steps in a quantitative occupational exposure assessment?
- Sample collection → Data analysis → Hazard identification → Control recommendation
- Hazard identification → Exposure measurement → Data evaluation against standards → Control recommendation (Correct answer)
- Control recommendation → Hazard identification → Sampling → Evaluation
- Exposure measurement → Hazard identification → Risk ranking → Sampling
Correct answer: Hazard identification → Exposure measurement → Data evaluation against standards → Control recommendation
A systematic quantitative exposure assessment follows: identify hazards, measure exposures, compare data against occupational exposure limits, then recommend and implement controls.
HSE Occupational Health and Hygiene 3
A short-term exposure limit (STEL) is defined as the maximum concentration a worker may be exposed to for up to how long without suffering irritation, tissue damage, or narcosis?