DRS1713 – Chapter 2 : Physical Hazards (Noise, Vibration, Heat Stress, Radiation)

Learning Outcomes

• After Chapter 2 you should be able to:
  • Describe the four physical hazards: Noise, Vibration, Heat Stress, Radiation.
  • Explain defining characteristics, health effects and control measures for each.
  • Cite Malaysian legislation and key exposure limits linked to every hazard.
• Inspirational reminder: “The capacity to learn is a gift; the ability to learn is a skill; the willingness to learn is a choice.” — Brian Herbert

Overview of Workplace Hazard Classes

• Five broad categories found in industry/laboratories:
  • Physical (focus of this chapter)
  • Chemical
  • Biological
  • Ergonomic
  • Psychological

Recap – Physical Hazards Identified

• Noise
• Heat Stress
• Vibration
• Radiation

NOISE HAZARD

Key Concepts & Definitions

• Noise = unwanted sound; sound becomes a hazard when intensity + duration ⟶ harm.
• Action Level (AL): 85\,\text{dB(A)} (8-h TWA).
• Permissible Exposure Limit (PEL):
  • 8-h TWA = 85\,\text{dB(A)}.
  • Ceiling limit = 140\,\text{dB(A)} (instantaneous).
• Instrumentation: Sound-Pressure-Level meter e.g. Pulsar Nova.
• General health endpoint: Noise-Induced Hearing Loss (NIHL).

Typical SPLs ≥ 85\,\text{dB(A)} (selected industries)

• Manufacture of non-metal products – 94\,\text{dB}
• Manufacture of metal cans/containers – 94\,\text{dB}
• Structural metal products, machinery, forging & stamping, furniture, textiles – 93\,\text{dB}
• Food manufacture, basic metal, fabricated metal, chemicals, aircraft, paper, printing – 92\,\text{dB} to 89\,\text{dB}

Everyday Noise Spectrum (illustrative)

• Rocket launch ≈ 180\,\text{dB} (instant damage)
• Jet engine at take-off ≈ 140\,\text{dB} (ceiling)
• Jackhammer ≈ 130\,\text{dB} — safe time < 1 s
• Rock concert ≈ 120\,\text{dB} — safe time ≈ 7 s
• Chain saw/Jet ski ≈ 110\,\text{dB} — safe time ≈ 90 s
• Subway/Power mower ≈ 90\,\text{dB} — safe time ≈ 8 h
• Every +3 dB above 85\,\text{dB} halves safe exposure time:
  T_{\text{safe}}(\text{dB}) = 8\,\text{h} \times 2^{\frac{85-\text{dB}}{3}}

Example calculation (Practical Q): Metal-can plant at 106\,\text{dB} ⇒ T_{\text{safe}} = 8\,\text{h} / 2^{7} \approx 3.75\,\text{min} (≈ 3 min 45 s).

Occupational vs Non-occupational Sources

• Occupational: metal forging, tiling, air guns, jack-hammering, etc.
• Non-occupational: personal audio players, loud sports cars, concerts, night clubs.

Health Effects

• Auditory: gradual hearing loss, tinnitus.
• Non-auditory: hypertension, stress, depression, poor attention, reduced work performance, communication interference.

Hierarchy of Controls

• SUBSTITUTE / ELIMINATE – quieter processes/equipment.
• ENGINEERING – enclosures, damping panels, sound-absorbing ceilings/walls.
• ADMINISTRATIVE – rotate staff, shorten shifts, schedule noisy tasks off-peak.
• PPE – earplugs, earmuffs (last line of defence).

Governing Law

• Occupational Safety & Health (Noise Exposure) Regulations 2019.

VIBRATION HAZARD

Core Definitions

• Vibration = oscillatory motion of a solid; amplitude + frequency sufficient to harm.
• Two exposure categories:
  1. Hand-Arm Vibration (HAV)
  2. Whole-Body Vibration (WBV)

Hand-Arm Vibration (HAV)

• Sources: grinders, polishers, chainsaws, drills, road breakers, holding work during grinding/cutting.
• Symptoms: tingling, numbness, blanching of fingers (white-finger), weakened grip.

Whole-Body Vibration (WBV)

• Sources: sitting/standing/lying on vibrating platforms—vehicles, heavy equipment, boats.
• Effects: headaches, motion sickness, chronic back pain, GI upset, sleep/visual disturbance.

Other HAV/WBV Examples (daily life)

• HAV: electric toothbrush, power lawn-edger, impact wrench.
• WBV: long-haul truck driving, riding motorcycles, amusement-park rides.

Controls

• SUBSTITUTE/ELIMINATE – alternate vibrating/non-vibrating tools, automation.
• ENGINEERING – isolate mounts, dampers, regular maintenance & balancing.
• ADMINISTRATIVE – training; 10–15 min rest each hour; job rotation.
• PPE – anti-vibration or thick gloves (limited effectiveness).

Related Legislation

• OSHA 1994 (Objective 3: provide environment suitable for workers’ physiological & psychological needs).

HEAT STRESS HAZARD

Definition

• Heat stress occurs when heat retained by body > ability to dissipate.

Work Situations with Heat Stress

• Foundries, smelting, glass blowing, road paving, kitchen/catering, agriculture in tropics, boiler rooms, firefighting.

Symptoms/Stages

• Heat rash & skin irritation (sweat-blocked pores).
• Excessive fatigue / Heat exhaustion: dizziness, heavy sweating.
• Heat cramps: painful muscle spasms (electrolyte loss).
• Heat stroke: collapse, dry/hot skin, medical emergency.

Prevention – Employer Responsibilities

• Evaluate site WBGT, humidity, radiant sources.
• Provide sanitary cool drinking water & encourage hydration.
• Schedule heavy work during coolest hours; mandatory work/rest cycles.
• “Buddy system” monitoring.
• Engineering: shade canopies, spot-cooling A/C trailers, vented PPE, full-brim hard hats.

Prevention – Employee Actions

• Seek shade, drink plenty of water, wear loose/light clothing, take regular breaks.

Governing Law

• OSHA 1994 (Objective 3).

RADIATION HAZARD

Definition & Scope

• Emission of energy as EM waves or particles; ionising radiation (high energy) causes ionisation → tissue damage.

Electromagnetic Spectrum (ordered by ↑ energy)

• Non-ionising: Extremely‐low-freq. (power lines), radio (AM/FM/TV), microwaves, infrared, visible, some UV.
• Ionising: UV-C/B end, X-rays, gamma rays.

Particle vs Wave Radiations

• Alpha (\alpha): 2 p + 2 n; stopped by paper/outer skin; internal hazard if inhaled/ingested.
• Beta (\beta): high-energy e⁻; stopped by few mm aluminum/heavy clothing; can burn skin.
• Gamma (\gamma) & X-ray: high-energy EM; need thick dense shields.
• Neutron (n): free neutrons; moderated by water; shield by concrete/water/lead.

Typical Shield Thickness for \gamma-rays

• 13.8\,\text{ft} (4.2 m) water
• 6.6\,\text{ft} (2 m) concrete
• 1.3\,\text{ft} (0.4 m) lead

Health Effects

• Cancer, mutagenesis, central-nervous-system syndrome, skin burns, cataracts, hair loss, infertility, mental retardation in offspring.

Protective Strategy

• ALARA concept: keep exposure As Low As Reasonably Achievable via:
  • Time: minimize duration.
  • Distance: inverse-square law I \propto 1/r^{2}.
  • Shielding: materials above.
• Observe dose limits; never exceed PELs legislated.

Legislation

• Atomic Energy Licensing Act 1984:
  • Radiation Protection (Licensing) Regulations 1986.
  • Radiation Protection (Basic Safety Standards) Regulations 1988.

Linking Back to the Laboratory

• Likely lab exposures & suggested controls:
  • Noise: sonicators, centrifuges ⇒ use enclosure, schedule use after hours, wear earplugs.
  • Vibration: handheld mixers, orbital shakers ⇒ anti-vibration pads; limit handling time.
  • Heat stress: autoclave room, furnace area ⇒ ventilation, hydration, rest breaks.
  • Radiation: UV transilluminator, X-ray diffractometer ⇒ shielding, interlocks, dosimeters, ALARA.

Summary Formulae & Figures Worth Memorising

• Safe-time halving rule: T_{\text{safe}}(\text{dB}) = 8\,\text{h} \times 2^{(85-\text{dB})/3}.
• Inverse-square for radiation intensity: I2 = I1 \big( r1 / r2 \big)^2.
• HAV exposure points system (not covered numerically here but remember concept: A(8) vibration dose normalised to 8-h shift).

Master these notes and you can confidently identify, evaluate and control physical hazards in both industrial and laboratory environments. Stay safe!