- Practice · 5 marks
Hazardous waste: definition and classification
Short answer
Hazardous waste poses danger to health or environment. Classified by property: ignitable (solvents, flash point <60°C), corrosive (pH ≤2 or ≥12.5), reactive (cyanides, explosives), toxic (heavy metals, pesticides), infectious (hospital sharps) and radioactive (lab waste). Sources: chemical, electroplating, tannery, hospitals, agriculture, households.
Define hazardous waste. Classify hazardous wastes according to their characteristics and give examples of their sources.
Hazardous waste is any solid, liquid or gaseous waste that, because of its quantity or its chemical, physical or biological nature, can cause or contribute to illness or death, or can pose a danger to human health or the environment if improperly stored, treated, transported or disposed of.
Classification by characteristics (as used by the US EPA and in textbooks)
| Class | Property | Examples |
|---|---|---|
| Ignitable | Flash point < 60 C; burns easily | Solvents, petrol, oils, paints |
| Corrosive | pH 2 or 12.5; attacks metals/tissue | Acids, alkalis, battery acid |
| Reactive | Unstable, explosive, reacts with water or releases toxic gas | Explosives, cyanides, sulphides, peroxides |
| Toxic | Poisonous at low dose; fails the leaching test (TCLP) | Heavy metals (Pb, Hg, Cd), pesticides, PCBs |
| Infectious (biomedical) | Contains pathogens | Hospital sharps, used dressings, cultures |
| Radioactive | Emits ionising radiation | Waste from hospitals, laboratories, research |
By form: solid, liquid, sludge, gaseous.
Sources
- Industries: chemical, pesticide, paint, tannery, electroplating, battery manufacture, metal finishing.
- Hospitals and laboratories: biomedical waste, chemicals, radioactive isotopes.
- Agriculture: pesticides, containers.
- Households: batteries, paints, e-waste, fluorescent lamps (small amounts).
- Mining and energy: tailings, fly ash, used oil.
✓ Answer checked by Claude Opus 5.5 (high effort)
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