NEBOSH Chemical Hazards 1 — Questions and Answers
Question 1: What is the UN Globally Harmonized System (GHS) of Classification and Labelling of Chemicals?
- An internationally standardized system for classifying chemical hazards and communicating them through standardized labels (pictograms, signal words, hazard and precautionary statements) and Safety Data Sheets (Correct answer)
- A Gulf-specific chemical safety system
- A voluntary labelling system with no legal basis
- A system only applicable to pharmaceutical products
Correct answer: An internationally standardized system for classifying chemical hazards and communicating them through standardized labels (pictograms, signal words, hazard and precautionary statements) and Safety Data Sheets
UN GHS standardizes chemical hazard classification and communication globally, replacing the previous patchwork of national systems. It defines: hazard classes and categories, standardized pictograms (skull, flame, corrosive), signal words (Danger/Warning), hazard statements (H-phrases), and precautionary statements (P-phrases) on labels and Section 2 of the 16-section SDS.
Question 2: What are the main health effects of solvent exposure in the workplace?
- Central nervous system depression (dizziness, headache, unconsciousness), liver and kidney damage from chronic exposure, dermatitis from skin defatting, and carcinogenicity for some solvents (Correct answer)
- Solvents only cause skin irritation
- Solvents are non-toxic below visible vapour levels
- Solvent exposure only affects workers over 50
Correct answer: Central nervous system depression (dizziness, headache, unconsciousness), liver and kidney damage from chronic exposure, dermatitis from skin defatting, and carcinogenicity for some solvents
Organic solvents (toluene, xylene, acetone, chlorinated solvents, n-hexane) are absorbed via inhalation and skin. Acute CNS effects: dizziness, impaired judgment, unconsciousness. Chronic effects: peripheral neuropathy (n-hexane), liver/kidney damage (chlorinated solvents), leukaemia (benzene — Group 1 carcinogen). Skin contact causes irritant contact dermatitis.
Question 3: What is the correct control hierarchy for chemical exposures in the workplace?
- Elimination, substitution with less hazardous substance, engineering controls (enclosure, LEV), administrative controls (reducing time, rotation), PPE — as last resort (Correct answer)
- PPE is the first and most important control
- Administrative controls are more effective than engineering controls
- Monitoring is the primary control for chemical hazards
Correct answer: Elimination, substitution with less hazardous substance, engineering controls (enclosure, LEV), administrative controls (reducing time, rotation), PPE — as last resort
The COSHH hierarchy for chemical control: 1) Eliminate the hazardous substance (change process), 2) Substitute with less hazardous substance, 3) Engineering controls (enclosed process, local exhaust ventilation capturing contaminant at source), 4) Administrative controls (job rotation, reduced hours), 5) PPE (respiratory protection, gloves, protective clothing). Higher controls provide more reliable protection.
Question 4: What is 'local exhaust ventilation' (LEV) and what is its purpose?
- A system that captures airborne contaminants at or near the point of generation before they disperse into the general workplace air — more effective than general dilution ventilation (Correct answer)
- A general workplace ventilation system that dilutes contaminated air
- LEV is used only to control temperature
- LEV is only required in chemical laboratories
Correct answer: A system that captures airborne contaminants at or near the point of generation before they disperse into the general workplace air — more effective than general dilution ventilation
LEV captures dust, fumes, vapours, and mist at the source using a hood or enclosure, transporting them through ductwork to filtration and safe discharge. Capture at source prevents worker exposure. LEV must be designed for the specific contaminant and process, regularly inspected, and tested (thorough examination and testing at least every 14 months under COSHH Regulations).
Question 5: What are the GHS pictogram requirements for a substance classified as acutely toxic (category 1)?
- Skull and crossbones (GHS06) with signal word 'Danger' (Correct answer)
- Exclamation mark (GHS07) with signal word 'Warning'
- Flame (GHS02)
- Health hazard (GHS08) for carcinogens
Correct answer: Skull and crossbones (GHS06) with signal word 'Danger'
GHS acutely toxic substances (categories 1–3, highest toxicity) carry the skull and crossbones pictogram (GHS06) with the signal word 'Danger.' Category 4 (lower toxicity) uses the exclamation mark (GHS07) with 'Warning.' Categories 1–3 require urgent medical treatment on exposure.
Question 6: What is 'reactive' or 'unstable' chemical hazard and how is it identified on SDS?
- Chemicals that can detonate, deflagrate, or undergo violent decomposition — identified in Section 2 (hazard identification), Section 7 (handling/storage), and Section 10 (reactivity) of the SDS (Correct answer)
- Reactive chemicals only pose fire risk
- Reactive chemicals are always corrosive
- All chemicals are reactive under certain conditions — no specific SDS sections address this
Correct answer: Chemicals that can detonate, deflagrate, or undergo violent decomposition — identified in Section 2 (hazard identification), Section 7 (handling/storage), and Section 10 (reactivity) of the SDS
Reactive/unstable chemicals (organic peroxides, self-reactive substances, explosives, pyrophoric materials) can undergo violent uncontrolled reactions from heat, shock, contamination, or incompatibility. SDS Sections 2 (classification), 7 (handling/storage precautions including temperature control, incompatibilities), and 10 (stability and reactivity data) are critical for safe management.
NEBOSH Chemical Hazards 1
What is the UN Globally Harmonized System (GHS) of Classification and Labelling of Chemicals?