CIH Hazards & Exposures 2 — Questions and Answers
Question 1: A worker is exposed to benzene at 0.4 ppm TWA over an 8-hour shift. The OSHA PEL for benzene is 1 ppm. Which statement best describes this situation?
- The exposure is in compliance but the OSHA Action Level of 0.5 ppm has not been exceeded (Correct answer)
- The exposure exceeds the OSHA PEL and immediate controls are required
- The exposure exceeds the NIOSH REL but not the OSHA PEL
- No action is needed because benzene is not regulated below 1 ppm
Correct answer: The exposure is in compliance but the OSHA Action Level of 0.5 ppm has not been exceeded
The OSHA benzene PEL is 1 ppm TWA and the Action Level is 0.5 ppm; at 0.4 ppm the worker is below both thresholds, so compliance is maintained.
Question 2: Which biological monitoring specimen is MOST appropriate for assessing recent lead exposure in a worker?
- Blood lead level (BLL) (Correct answer)
- Urine delta-aminolevulinic acid (ALA)
- Urine coproporphyrin
- Zinc protoporphyrin (ZPP)
Correct answer: Blood lead level (BLL)
Blood lead level is the primary OSHA-mandated biomarker for recent lead exposure because it reflects current absorbed dose.
Question 3: A confined space contains 16% oxygen. How should this atmosphere be classified?
- Oxygen-deficient; requires supplied-air respirator or SCBA (Correct answer)
- Acceptable; normal air is 20.9% but 16% is within permissible range
- Oxygen-enriched; fire hazard controls are needed
- Immediately Dangerous to Life or Health (IDLH)
Correct answer: Oxygen-deficient; requires supplied-air respirator or SCBA
OSHA defines an oxygen-deficient atmosphere as less than 19.5% O₂, requiring supplied-air or SCBA before entry.
Question 4: A noise dosimeter shows a worker received a dose of 150% over an 8-hour shift. What is the calculated TWA noise level?
- Approximately 93.5 dBA (Correct answer)
- Exactly 90 dBA
- Exactly 95 dBA
- Approximately 85 dBA
Correct answer: Approximately 93.5 dBA
Using the formula TWA = 16.61 × log(D/100) + 90, a dose of 150% yields approximately 93.5 dBA TWA.
Question 5: Which type of non-ionizing radiation is most associated with photokeratitis ('welder's flash')?
- Ultraviolet-C (UV-C) (Correct answer)
- Infrared radiation
- Microwave radiation
- Visible light
Correct answer: Ultraviolet-C (UV-C)
UV-C (100–280 nm) is most energetic in the ultraviolet range and causes photokeratitis, the painful corneal inflammation known as welder's flash.
Question 6: A manufacturing plant uses isocyanates in a spray painting operation. What is the primary route of exposure of greatest concern?
- Inhalation of aerosols and vapors (Correct answer)
- Dermal absorption through intact skin
- Ingestion from hand-to-mouth contact
- Eye contact causing systemic absorption
Correct answer: Inhalation of aerosols and vapors
Isocyanates are potent respiratory sensitizers, and inhalation of spray aerosols or vapors is the primary route leading to occupational asthma.
Question 7: Which physical hazard describes low-frequency whole-body vibration (1–80 Hz) that can cause spinal disorders in heavy equipment operators?
- Whole-body vibration (WBV) (Correct answer)
- Hand-arm vibration (HAV)
- Segmental vibration disorder
- Raynaud's phenomenon
Correct answer: Whole-body vibration (WBV)
Whole-body vibration transmitted through the seat to the spine is linked to lumbar disorders in operators of vehicles and heavy equipment.
CIH Hazards & Exposures 2
A worker is exposed to benzene at 0.4 ppm TWA over an 8-hour shift.
The OSHA PEL for benzene is 1 ppm.
Which statement best describes this situation?