In this module
Objectives covered: LO 3.10.1. By the end you will be able to:
- Explain how health hazards are anticipated, recognised, evaluated and controlled.
- Apply noise limits and the hearing conservation programme.
- Describe air contaminant limits and heat stress controls.
10.1 What industrial hygiene does
Industrial hygiene protects workers from health hazards that often act slowly: noise, dust, fumes, vapours, heat, radiation and biological agents. The four steps are anticipate, recognise, evaluate (measure exposure) and control.
10.2 Noise
- Action level: 85 dB(A) as an 8-hour time-weighted average (TWA). Start a hearing conservation programme: monitoring, annual audiograms, hearing protectors, training and records.
- Permissible exposure limit (PEL): 90 dB(A) TWA. Above this, engineering or administrative controls are required, with hearing protection.
- OSHA uses a 5 dB exchange rate: 95 dB(A) is allowed for 4 hours, 100 dB(A) for 2 hours.
10.3 Air contaminants
OSHA PELs are listed in 1910.1000 Tables Z-1 to Z-3, and specific standards cover substances such as respirable crystalline silica (PEL 50 µg/m³, 1910.1053), lead, benzene and asbestos. Many companies also use the lower ACGIH TLVs. Control by substitution, enclosure, local exhaust ventilation and wet methods first; respirators come last, under a written programme.
10.4 Heat stress
Heat exhaustion and heat stroke are serious risks in Bangladesh summers, boiler rooms, foundries and laundries. Use the "Water, Rest, Shade" approach: cool drinking water, scheduled rest breaks, shaded or cooled rest areas, acclimatisation for new workers (about 20% exposure on day one, building up over a week), and training on symptoms. Heat stroke (confusion, hot dry skin, collapse) is a medical emergency: call for help and cool the person at once.
- 1910.95 occupational noise; 1910.1000 air contaminants; 1910.1053 silica; 1910.134 respiratory protection.
- OSHA heat illness guidance and the General Duty Clause; ACGIH TLVs and the WBGT heat index.
- Bangladesh Labour Act 2006, Sections 52 to 54: ventilation, temperature, dust and fumes.
Weaving sheds in Narsingdi often exceed 95 dB(A). One mill measured noise, fitted acoustic panels and enclosed the loudest looms, and introduced earmuffs with annual hearing tests. Weavers who had started to lose high-frequency hearing were moved to quieter areas, and new cases were caught early.
Learning Check
Answer these two questions to check your understanding. You can try again as many times as you like.