CIH Physical Agents: Noise and Radiation 2 — Questions and Answers
Question 1: A worker is exposed to 95 dBA for 4 hours and 85 dBA for 4 hours in an 8-hour shift. What is the noise dose using OSHA's permissible exposure limits?
- 50%
- 75% (Correct answer)
- 100%
- 125%
Correct answer: 75%
At 95 dBA the PEL is 4 hours (C1/T1 = 4/4 = 1.0) and at 85 dBA the PEL is 16 hours (C2/T2 = 4/16 = 0.25), giving a total dose of 75%.
Question 2: Which type of hearing protection device typically provides the highest noise reduction when properly fitted?
- Earmuffs
- Foam earplugs (Correct answer)
- Pre-molded earplugs
- Canal caps
Correct answer: Foam earplugs
Properly fitted foam earplugs generally achieve the highest noise reduction ratings (NRR), often 29–33 dB, because they expand to fill the ear canal.
Question 3: What is the primary biological mechanism by which excessive noise causes permanent hearing loss?
- Rupture of the tympanic membrane
- Destruction of hair cells in the organ of Corti (Correct answer)
- Damage to the auditory nerve sheath
- Calcification of the ossicles
Correct answer: Destruction of hair cells in the organ of Corti
Excessive noise destroys the outer hair cells in the organ of Corti, which cannot regenerate, causing permanent sensorineural hearing loss.
Question 4: Under OSHA 29 CFR 1910.95, at what action level must employers implement a Hearing Conservation Program?
- 80 dBA TWA
- 85 dBA TWA (Correct answer)
- 90 dBA TWA
- 95 dBA TWA
Correct answer: 85 dBA TWA
OSHA requires a Hearing Conservation Program when worker TWA exposures equal or exceed 85 dBA (the action level).
Question 5: A radiation worker receives 2 mSv from external gamma exposure and 3 mSv from internal deposition of a radionuclide in one year. What is the total effective dose equivalent?
- 2 mSv
- 3 mSv
- 5 mSv (Correct answer)
- 6 mSv
Correct answer: 5 mSv
Total effective dose equivalent is the sum of external and internal dose components: 2 + 3 = 5 mSv.
Question 6: Which ionizing radiation type has the greatest penetrating power in tissue?
- Alpha particles
- Beta particles
- Gamma rays (Correct answer)
- Neutrons
Correct answer: Gamma rays
Gamma rays are high-energy electromagnetic radiation that can penetrate deeply through the body and require dense shielding materials like lead or concrete.
Question 7: The NIOSH recommended exposure limit (REL) for noise uses an exchange rate of 3 dB, whereas OSHA uses 5 dB. What does this mean practically?
- NIOSH allows twice the exposure time at each dB increment
- NIOSH halves allowable exposure time for every 3 dB increase in level (Correct answer)
- NIOSH and OSHA produce identical permissible exposure durations
- OSHA is more protective than NIOSH at high noise levels
Correct answer: NIOSH halves allowable exposure time for every 3 dB increase in level
With a 3 dB exchange rate, NIOSH halves the allowable duration for every 3 dB increase in level, which is more protective than OSHA's 5 dB exchange rate.
CIH Physical Agents: Noise and Radiation 2
A worker is exposed to 95 dBA for 4 hours and 85 dBA for 4 hours in an 8-hour shift.
What is the noise dose using OSHA's permissible exposure limits?