CIH Physical Agents: Noise and Radiation 3 — Questions and Answers
Question 1: Which audiometric finding is considered a 'standard threshold shift' (STS) under OSHA's Hearing Conservation Amendment?
- An average shift of 5 dB or more at 500, 1000, and 2000 Hz
- An average shift of 10 dB or more at 2000, 3000, and 4000 Hz (Correct answer)
- Any shift of 15 dB at any single frequency
- A shift of 20 dB at 4000 Hz only
Correct answer: An average shift of 10 dB or more at 2000, 3000, and 4000 Hz
OSHA defines STS as an average shift of 10 dB or more at 2000, 3000, and 4000 Hz compared to the baseline audiogram.
Question 2: What is the primary purpose of a baseline audiogram in a hearing conservation program?
- To determine the worker's fitness for duty
- To serve as a reference for detecting future threshold shifts (Correct answer)
- To calculate the noise dose for regulatory compliance
- To select the appropriate type of hearing protection
Correct answer: To serve as a reference for detecting future threshold shifts
The baseline audiogram establishes the worker's initial hearing threshold levels so that future audiograms can be compared to detect noise-induced changes.
Question 3: Ultraviolet radiation in occupational settings is most commonly associated with which health effect?
- Cataract formation only
- Erythema (sunburn) and increased skin cancer risk (Correct answer)
- Peripheral neuropathy
- Deep tissue burns
Correct answer: Erythema (sunburn) and increased skin cancer risk
Occupational UV radiation exposure primarily causes erythema, photokeratitis, and increases the risk of skin cancer, particularly from UVB wavelengths.
Question 4: A survey meter reads 25 mR/hr at 1 meter from an unshielded gamma source. Using the inverse square law, what is the dose rate at 5 meters?
- 5 mR/hr
- 1 mR/hr (Correct answer)
- 0.5 mR/hr
- 2.5 mR/hr
Correct answer: 1 mR/hr
By the inverse square law: 25 × (1/5)² = 25 × 0.04 = 1 mR/hr at 5 meters.
Question 5: Which non-ionizing radiation type is regulated by OSHA in welding operations primarily because of risk to the eyes?
- Microwave radiation
- Radiofrequency radiation
- Infrared radiation
- Ultraviolet radiation (Correct answer)
Correct answer: Ultraviolet radiation
UV radiation from welding arcs causes photokeratitis ('arc eye' or 'welder's flash'), making eye protection mandatory in welding operations.
Question 6: The half-value layer (HVL) concept in radiation shielding refers to:
- The distance at which dose rate is halved
- The thickness of material that reduces radiation intensity by 50% (Correct answer)
- The time required to reduce radioactive contamination by half
- The energy at which photons are equally absorbed and transmitted
Correct answer: The thickness of material that reduces radiation intensity by 50%
The half-value layer is the thickness of a shielding material that attenuates a beam of radiation to half its original intensity.
Question 7: A worker's personal noise dosimeter shows a reading of 150% dose at the end of an 8-hour shift. Which of the following correctly interprets this result?
- The worker's exposure was within OSHA's PEL
- The worker's exposure exceeded OSHA's PEL and engineering controls must be considered (Correct answer)
- The worker's TWA was exactly 90 dBA
- Hearing protection automatically makes this exposure compliant
Correct answer: The worker's exposure exceeded OSHA's PEL and engineering controls must be considered
A dose of 150% exceeds OSHA's 100% permissible dose, indicating the worker's TWA exceeded 90 dBA, requiring feasible engineering and administrative controls.
CIH Physical Agents: Noise and Radiation 3
Which audiometric finding is considered a 'standard threshold shift' (STS) under OSHA's Hearing Conservation Amendment?