Environmental and Occupational Hazards: Noise, Vibration, Radiation, and Chemicals
Noise and vibration
Noise is the most common aerospace occupational hazard. Understand the A-weighted decibel, the equal-energy principle, and the 3 dB exchange rate: each 3 dB increase halves permissible exposure time. An 85 dBA time-weighted average over eight hours is a common action level, with hearing protection and audiometric surveillance required above it. Distinguish impact noise, which needs C-weighted or peak limits, from continuous noise. Vibration divides into whole-body vibration, linked to fatigue and spinal complaints in aircrew and drivers, and hand-arm vibration, linked to Raynaud-type symptoms in maintenance workers.
Radiation
Aircrew and astronauts face cosmic radiation, with dose increasing strongly with altitude and latitude. Solar particle events can deliver large acute doses, especially outside low Earth orbit. Apply ALARA, distinguish occupational from public dose limits, and recognize that pregnant crew members need individual risk counseling. Question writers often imply radiation is negligible at cruise altitudes; it is measurable and regulated in many jurisdictions.
Chemical and biological hazards
Consider jet fuel and solvent exposure, hydraulic fluids, carbon monoxide from exhaust or bleed air, ozone in cabin supply air, and contaminated bleed air. Carbon monoxide poisoning is easily missed because symptoms are nonspecific. Biological hazards include communicable disease transmission in cabins and occupational exposure during aeromedical transport. Thermal hazards, laser and radiofrequency exposure, and noise-induced communication errors round out the list.
Traps
- Using a 5 dB exchange rate or confusing A- with C-weighting.
- Treating radiation limits for crew as identical to public limits.
- Assuming cabin air is always clean; bleed-air contamination is a recognized concern.
- Attributing headache and nausea to fatigue when carbon monoxide is possible.
Worked example
A worker is exposed to 88 dBA. Since 88 is 3 dB above 85, permissible exposure halves from eight hours to four. This is the arithmetic most often tested.