NEBOSH CC Dust & Noise in Construction 2 — Questions and Answers
Question 1: What is the maximum Workplace Exposure Limit (WEL) for wood dust in the UK under EH40?
- 3 mg/m³ (8-hour TWA) for hardwood dust, 5 mg/m³ for softwood dust (Correct answer)
- 1 mg/m³ for all wood dust
- 10 mg/m³ for all wood dust
- 0.5 mg/m³ for all wood dust
Correct answer: 3 mg/m³ (8-hour TWA) for hardwood dust, 5 mg/m³ for softwood dust
Under EH40, the WEL for hardwood dust (and mixtures containing hardwood) is 3 mg/m³ as an 8-hour TWA. For softwood dust, the WEL is 5 mg/m³ as an 8-hour TWA. Hardwood dust is a Group 1 carcinogen.
Question 2: Why is hardwood dust considered more hazardous than softwood dust?
- Hardwood dust is classified as a known human carcinogen (Group 1) linked to sinonasal cancer (Correct answer)
- Hardwood particles are larger and cause more irritation
- Hardwood dust is heavier and settles more quickly
- Hardwood dust is only hazardous at very high concentrations
Correct answer: Hardwood dust is classified as a known human carcinogen (Group 1) linked to sinonasal cancer
Hardwood dust (including oak and beech) is classified as a Group 1 known human carcinogen by the International Agency for Research on Cancer (IARC). Long-term exposure is associated with sinonasal cancer (cancer of the nose and sinuses).
Question 3: What does the term 'inhalable dust' mean in occupational hygiene?
- Dust particles small enough to be inhaled through the nose and mouth, settling in the upper airways (Correct answer)
- Dust particles that reach the alveoli of the lungs
- Only particles visible to the naked eye
- Particles larger than 10 micrometres that are filtered by the nose
Correct answer: Dust particles small enough to be inhaled through the nose and mouth, settling in the upper airways
Inhalable dust refers to the fraction of airborne particles that can be inhaled through the nose and mouth and deposited in the upper respiratory tract. It includes particles up to approximately 100 micrometres in aerodynamic diameter.
Question 4: What is 'respirable dust' in occupational hygiene?
- The fraction of airborne dust small enough to penetrate to the alveoli of the lungs (Correct answer)
- All dust particles that enter the nose
- Dust particles larger than 10 micrometres
- Only dust visible to the naked eye
Correct answer: The fraction of airborne dust small enough to penetrate to the alveoli of the lungs
Respirable dust is the fraction of inhaled particles that is small enough (typically below 10 micrometres aerodynamic diameter) to penetrate beyond the larynx and reach the alveoli of the lungs, where gas exchange occurs.
Question 5: What is the lower action value (LAV) for noise exposure under the Control of Noise at Work Regulations 2005?
- 80 dB(A) daily or weekly average exposure (Correct answer)
- 85 dB(A) daily or weekly average exposure
- 87 dB(A) daily or weekly average exposure
- 70 dB(A) daily or weekly average exposure
Correct answer: 80 dB(A) daily or weekly average exposure
The lower exposure action value (LAV) for noise is 80 dB(A) as a daily or weekly average. At this level, employers must make hearing protection available and provide workers with information about the risks. Action is required but hearing protection is not mandatory.
Question 6: What is the upper action value (UAV) for noise under the Control of Noise at Work Regulations 2005?
- 85 dB(A) daily or weekly average exposure (Correct answer)
- 80 dB(A)
- 87 dB(A)
- 90 dB(A)
Correct answer: 85 dB(A) daily or weekly average exposure
The upper exposure action value (UAV) is 85 dB(A) as a daily or weekly average. At this level, employers must take action to reduce noise exposure, designate hearing protection zones and ensure workers wear hearing protection.
NEBOSH CC Dust & Noise in Construction 2
What is the maximum Workplace Exposure Limit (WEL) for wood dust in the UK under EH40?