Occupational Health, Hygiene and Industrial Diseases
What occupational health covers
Anticipate, recognise, evaluate and control workplace exposures. Routes of entry: inhalation, absorption through skin, ingestion, injection.
Exposure limits and monitoring
TLV-TWA is an 8-hour shift average; STEL a 15-minute short-term limit; a ceiling is a concentration never to be exceeded. For mixed exposures use the dose rule: Σ(C/T) ≤ 1. Distinguish air monitoring (the workplace) from biological monitoring (the worker) from health surveillance (audiometry, spirometry, skin checks).
Noise
85 dBA over 8 hours is the usual action level, 90 dBA the common limit. A 3 dB increase doubles sound energy, so halving exposure time restores the dose. Noise-induced hearing loss is permanent; early sign is difficulty hearing conversation in noise.
Classic occupational diseases
- Respirable crystalline silica → silicosis.
- Asbestos → asbestosis, mesothelioma, lung cancer (long latency).
- Coal dust → coal worker's pneumoconiosis.
- Lead → anaemia, neuropathy, kidney damage.
- Hand-arm vibration → HAVS ("white finger").
- Isocyanates, flour dust → occupational asthma.
- Solvents and wet work → dermatitis; benzene → leukaemia.
Traps
Mixing TWA with STEL; assuming disease appears immediately (latency); thinking PPE "cures" exposure; confusing health surveillance with a pre-employment medical.
Rule of thumb
Control at source first; measure before you decide, then measure again after controls to prove they worked.