CIEE Environmental Factors & Human Performance 4 — Questions and Answers
Question 1: A production line worker develops tingling and numbness in fingers after 3 months on a vibrating conveyor. ISO 5349 daily vibration exposure A(8) is 4 m/s². What stage of Hand-Arm Vibration Syndrome (HAVS) does this suggest?
- Stockholm Workshop Scale Stage 1 (vascular) — intermittent tingling with or without numbness (Correct answer)
- Stockholm Workshop Scale Stage 3 — frequent attacks with reduced sensory perception
- Stockholm Workshop Scale Stage 0 — no symptoms
- Stockholm Workshop Scale Stage 4 — severe, most days with reduced grip strength
Correct answer: Stockholm Workshop Scale Stage 1 (vascular) — intermittent tingling with or without numbness
Early neurological symptoms (tingling, occasional numbness) with no blanching correspond to Stage 1SN on the Stockholm Scale, consistent with early HAVS from moderate vibration exposure.
Question 2: Which parameter determines the Recommended Exposure Limit (REL) for chemical mixtures in relation to ergonomic heat stress assessments?
- Metabolic heat production increases absorption rate of skin-permeable chemicals (Correct answer)
- Chemical RELs are set independently of environmental temperature
- Heat increases pulmonary ventilation, reducing inhalation exposure time needed to hit TLV
- Cold temperatures increase dermal absorption more than heat does
Correct answer: Metabolic heat production increases absorption rate of skin-permeable chemicals
Elevated metabolic rate during heat stress increases cardiac output and pulmonary ventilation, which can increase inhalation dose rates for airborne chemicals, potentially making standard RELs insufficient.
Question 3: What is the primary limitation of using A-weighted decibel measurements (dBA) for assessing low-frequency noise in ergonomic evaluations?
- A-weighting heavily attenuates frequencies below 250 Hz, underestimating low-frequency noise impacts on annoyance and cognitive performance (Correct answer)
- A-weighting overestimates high-frequency noise damage risk
- A-weighting cannot be measured with standard sound level meters
- A-weighting is only valid for impulse noise, not continuous noise
Correct answer: A-weighting heavily attenuates frequencies below 250 Hz, underestimating low-frequency noise impacts on annoyance and cognitive performance
The A-weighting filter was designed to model hearing damage risk, but significantly de-emphasizes low-frequency content that contributes to annoyance, vibrotactile effects, and cognitive distraction.
Question 4: An ergonomist recommends task rotation to reduce cumulative heat stress. Which physiological principle supports this intervention?
- Allowing partial core temperature recovery between exposures limits cumulative heat storage (Correct answer)
- Task rotation eliminates the need for hydration protocols
- Rotating workers prevents acclimatization and maintains safe core temperature variance
- Heat production is lower during rotating tasks because workers move more slowly
Correct answer: Allowing partial core temperature recovery between exposures limits cumulative heat storage
Core temperature rises during hot work; rotation to a cooler task or rest allows partial dissipation of stored heat, preventing progressive thermal accumulation toward dangerous levels.
Question 5: A warehouse uses high-intensity discharge (HID) lamps with a 15-minute warm-up period. Workers must perform visual inspection immediately after a power outage. What is the primary ergonomic hazard?
- Sudden transition from emergency lighting to complete darkness before HID lamps restrike, causing dark adaptation loss and accident risk (Correct answer)
- HID lamps emit excessive UV during warm-up causing temporary photokeratitis
- Mercury vapor released during HID lamp warm-up degrades air quality
- Flicker from HID lamps during warm-up phase causes seizure risk in all workers
Correct answer: Sudden transition from emergency lighting to complete darkness before HID lamps restrike, causing dark adaptation loss and accident risk
HID lamps require up to 15 minutes to restart after power loss; workers transitioning between lighting levels in this period face severely impaired visibility and dark adaptation that increases accident risk.
Question 6: Which of the following describes the ergonomic impact of 'thermal asymmetry' in an office workstation environment?
- Uneven radiant temperature differential (>10°C between warm and cool sides) causes postural compensation and discomfort even within a comfortable mean radiant temperature range (Correct answer)
- Thermal asymmetry only affects workers in outdoor environments
- A 5°C difference between floor and ceiling temperatures is the primary concern
- Thermal asymmetry is acceptable as long as air temperature is within the comfort zone
Correct answer: Uneven radiant temperature differential (>10°C between warm and cool sides) causes postural compensation and discomfort even within a comfortable mean radiant temperature range
ISO 7730 identifies radiant temperature asymmetry >10°C as a source of localized thermal discomfort that triggers postural adjustments and reduces concentration even when mean temperatures are acceptable.
Question 7: Under NIOSH criteria for a recommended WBV exposure limit, which daily A(8) value (m/s²) marks the action level at which controls should be implemented?
- 0.5 m/s² (Correct answer)
- 1.15 m/s²
- 2.5 m/s²
- 0.1 m/s²
Correct answer: 0.5 m/s²
The EU Physical Agents Directive (and NIOSH-referenced guidance) sets a daily WBV action value at 0.5 m/s² A(8), triggering mandatory risk reduction measures.
CIEE Environmental Factors & Human Performance 4
A production line worker develops tingling and numbness in fingers after 3 months on a vibrating conveyor.
ISO 5349 daily vibration exposure A(8) is 4 m/s².
What stage of Hand-Arm Vibration Syndrome (HAVS) does this suggest?