UPSC Prelims 2022 Q98: Science & Technology – Materials & Engineering
Consider the following statements:
1. Other than those made by humans, nanoparticles do not exist in nature.
2. Nanoparticles of some metallic oxides are used in the manufacture of some cosmetics.
3. Nanoparticles of some commercial products which enter the environment are unsafe for
humans.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 3 only
- (c) 1 and 2
- (d) 2 and 3
Answer: (d) 2 and 3
Explanation
Nanoparticles: facts and myths
| Statement | Verdict | Reason |
|---|---|---|
| 1. Nanoparticles exist only when made by humans | Incorrect | They occur naturally in volcanic ash, sea spray, forest-fire smoke and dust |
| 2. Metal oxide nanoparticles are used in cosmetics | Correct | Titanium dioxide and zinc oxide nanoparticles are used in sunscreens |
| 3. Some nanoparticles entering the environment are unsafe for humans | Correct | Inhaled or ingested particles can cause inflammation and oxidative stress |
Scale:
| Item | Size |
|---|---|
| Nanoparticle | 1-100 nanometres |
| Human hair | About 80,000 nm wide |
Answer: (d) 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Statement 1 is false; volcanoes and sea spray produce natural nanoparticles.
- (b) Incorrect. Statement 2 is also true; TiO₂ and ZnO nanoparticles are used in sunscreens.
- (c) Incorrect. It keeps the false claim that nanoparticles are only man-made.
- (d) CORRECT. Nanoparticles are used in cosmetics and some can be harmful once released.
Key point
Nanoparticles (1-100 nm) occur naturally too; TiO₂ and ZnO nanoparticles are used in sunscreens; some pose health risks.
Remember
Nanoparticles: natural and man-made; used in sunscreens; some are toxic.
Common mistakes
- Assuming nanoparticles are purely a modern technology product.
- Not knowing sunscreens use metal-oxide nanoparticles.
- Thinking nano-sized material is always harmless because it is tiny.
Exam tip
'Only' or 'do not exist' claims about nature are usually false.
Sources
- Department of Science and Technology — Nano Mission
- NCERT Class XII — Chemistry, Ch 5 (Surface Chemistry: colloids)