Case 2 - Prioritising hazards in a Nairobi steel fabrication workshop
A steel fabrication workshop in Nairobi’s light industrial area employs 34 workers, including three welders who each work a full eight-hour shift. Personal noise measurements taken last month give 96 dB(A) Lep,d for the welders; the angle grinder is the main source. Welding is done in a corner of the general workshop with no local exhaust ventilation and only a ceiling fan for air movement. Two welders report a flu-like illness with fever, aching and a metallic taste that appears on Monday and clears by Wednesday; one has taken two days off. Gas cylinders of about 60 kg are manhandled from the delivery bay to the working bays, and the grinder’s guard was removed “to reach corners.” Earplugs sit in a box by the door but nobody wears them, welding goggles are shared, and there is no documented risk assessment. The workshop has never had a safety and health audit.
1. Rank the four main hazards by risk and justify the ranking. Which one requires action before any meeting or assessment?
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Rank by risk = likelihood × severity, weighted by exposure time and the number of people exposed.
- Unguarded angle grinder - act today. A bonded disc running at full speed can burst or snatch and open a hand or a thigh; severity is severe and permanent, and likelihood is high because removing the guard is a deliberate daily practice. This is imminent danger: withdraw the grinder from service, refit the correct guard, and deal with the practice as a supervision and discipline issue. No meeting is needed first.
- Welding fume with no extraction. Three welders, eight hours a day, in a corner moved only by a ceiling fan. The Monday fever, metallic taste and aching are the classic pattern of metal fume fever - harm has already occurred. Severity also covers chronic bronchitis, welding-related asthma and manganese effects. High risk.
- Noise at 96 dB(A) Lep,d. Risk is effectively certain. Under a 3 dB exchange rate the permitted duration halves for every 3 dB rise: 90 dB(A) for 8 hours, 93 for 4, 96 for about 2. An eight-hour shift at 96 dB(A) is therefore roughly four times the permitted daily dose. Hearing loss is irreversible, and the noise masks warnings and vehicle movement.
- 60 kg cylinders manhandled. The single-lift severity is high (disc or spinal injury) but the frequency is lower than the others. Still unacceptable: anything above about 25 kg should be moved mechanically.
Note the interaction: fume and noise come from the same bays, so extraction trunking and acoustic screening can be designed as one job.
2. Set out the control package for welding fume and noise, working through the hierarchy of control and explaining why PPE comes last.
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Work down the hierarchy; each step must be verified before relying on the next.
Eliminate / substitute
- Install a manifolded gas pack or bulk supply so 60 kg cylinders are never lifted.
- Specify a lower-fume process or filler where the work allows; use a low-noise grinder or a band saw where geometry permits.
Engineering
- Local exhaust ventilation at each bay - extraction hood or on-torch extraction - with make-up air, commissioned and then checked (face velocity measured) at defined intervals.
- Screen the welding bays off from the rest of the shop; mount grinders on benches with acoustic enclosures; provide cylinder trolleys and stands; refit the guard (a guard is an engineering control, not an optional extra).
Administrative
- A written risk assessment with review dates and named owners; hot-work permit; LEV maintenance schedule; job rotation to break continuous exposure; housekeeping; hearing conservation programme (signage from 85 dB(A), baseline audiometry, annual repeat); training for welders and supervisors; supervision that enforces the guard rule.
PPE last - because it fails silently
- The earplugs are already in the box and unworn; a shared goggle cannot fit every face. PPE depends on fit, correct donning, maintenance and discipline, all of which the workshop has already demonstrated it lacks.
- Still provide it: individually issued, fit-tested FFP3 or supplied-air welding helmets, correct shade, earplugs or earmuffs with enough attenuation (about 15–20 dB to bring 96 dB(A) towards 80–85), gloves, apron, boots. Train on fitting and record each issue.
Verify: repeat personal dosimetry and fume sampling after the engineering work, re-measure LEV, audit guard use weekly, and ask the welders whether the Monday symptoms have stopped.
3. What records and health checks should the committee insist on, and how would it know the controls are working?
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Records the committee should require
- The written risk assessment, signed and dated, with a review date and named owners for each action.
- Noise survey and dosimetry reports, before and after controls.
- LEV commissioning and maintenance records (face velocity readings, filter changes, breakdowns).
- Audiometry results held confidentially by the occupational health provider, with the worker told his own result.
- PPE issue register signed by each worker, showing type, size, fit-test date and replacement.
- Training records for welders and supervisors, including the guard rule and hearing protection.
- The accident/occupational disease register, including the two men with flu-like symptoms and any days lost.
- Statutory medical examinations for workers in hazardous occupations, arranged through a DOSHS-registered medical practitioner, and the safety and health audit required for the workplace.
How to know the controls are working - pick measures that can fail visibly
- Fume: symptoms stop; sampling below the relevant exposure limit; no visible haze at the bay.
- Noise: repeat dosimetry under 85 dB(A); attenuation check on the chosen plug/muff; audiograms stable.
- Grinder: zero unguarded grinders found in weekly supervisor checks.
- Handling: zero manual lifts of cylinders recorded in a month.
- Behaviour: near-miss reports rise (people trust the system) while lost-time cases fall - if reports fall to zero, suspect fear rather than safety.
The committee reviews these at each meeting, records the trend in the minutes, and sets the next verification date.