UPSC Prelims 2022 Q98: Nanoparticles — Occurrence, Uses, Safety
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?
- 1 only
- 3 only
- 1 and 2
- 2 and 3
Answer: (d) 2 and 3
Statement-wise explanation
- 1: incorrect — Nanoparticles occur widely in nature. Britannica's entry on nanoparticles names sea-salt aerosol from a few nanometres upward, smoke from volcanoes and fires, desert and field dust, and terpene particles given off by trees. Scientists sort nanoparticles into three groups: natural, incidental (unintended by-products such as diesel exhaust and welding fume) and engineered. Human-made particles are only part of the picture.
- 2: correct — Nanoparticles of titanium dioxide (TiO2) and zinc oxide (ZnO) are standard ingredients in sunscreens and some other cosmetics. Below about 100 nm these mineral filters still block UV light but no longer leave the white film that larger particles leave on the skin. TiO2 works mainly against UVB and ZnO against UVA, so the two are often combined for broad-spectrum protection.
- 3: correct — Engineered nanoparticles reach air, water and soil from products such as sunscreens, textiles and paints. Some of them are a hazard. Silver nanoparticles release silver ions, which are toxic, and studies report the particles building up in the liver, kidneys and lungs. Lab studies have found cell and DNA damage from ZnO and TiO2 nanoparticles. Nanoparticles are small enough to cross cell membranes, which is why regulators treat them as a separate risk category. The statement says only that 'some' are unsafe, which matches the evidence.
How to eliminate
Statement 1 makes an absolute claim: nanoparticles 'do not exist in nature' except those made by humans. Basic knowledge rules it out. Smoke, volcanic ash, sea spray and fine dust all contain particles of nanometre size, and nature always has some version of a physical size range. Once Statement 1 is out, the options that include it are gone, and only '3 only' and '2 and 3' remain. Statements 2 and 3 are both hedged with 'some', and UPSC statements hedged like this are usually true. Statement 2 is the fact to remember: TiO2 and ZnO nanoparticles are used in sunscreens. If you know about mineral sunscreens, or even just that titanium dioxide is a common cosmetic ingredient, you can choose between the two remaining options. Rule: when an S&T statement claims a natural phenomenon is exclusively human-made, it is almost always false.
Know more
Nanoparticles are particles with at least one dimension between about 1 and 100 nanometres (1 nm = one-billionth of a metre). At this size, a large share of the atoms sit on the surface. That changes the material's colour, reactivity, strength and how it behaves in the body. For example, gold looks red, and ZnO turns transparent.
Three sources of nanoparticles
| Type | Origin | Examples |
|---|---|---|
| Natural | Geological, marine and biological processes | Volcanic ash, sea-salt aerosol, forest-fire smoke, desert dust, terpenes from trees, viruses |
| Incidental | Unintended by-products of human activity | Diesel exhaust, welding fume, coal combustion, cooking smoke |
| Engineered | Made on purpose with a designed size and shape | TiO2/ZnO in sunscreens, nanosilver in textiles, carbon nanotubes, quantum dots, nano-fertilisers |
Common uses: sunscreens and cosmetics (TiO2, ZnO), antibacterial coatings and fabrics (silver), drug delivery and imaging (gold, iron oxide, lipid nanoparticles such as those in mRNA vaccines), electronics and displays (quantum dots), catalysts and batteries, and agriculture (IFFCO's liquid Nano Urea, commercial production from 2021).
Why safety is a concern: The tiny size and large surface area that make nanoparticles useful also let them enter the lungs, cross cell membranes and produce reactive oxygen species. Possible harms include oxidative stress, inflammation and DNA damage. How much harm depends on the material, size, shape and coating. Nanosilver is toxic to aquatic life through the silver ions it releases.
India's framework:
- Nano Mission (DST, launched 2007; Phase II approved 2014). After 31 March 2017 it continued as the National Programme on Nano Science and Technology.
- DST's Guidelines and Best Practices for Safe Handling of Nanomaterials in Research Laboratories and Industries (draft 2016).
- Guidelines for Evaluation of Nanopharmaceuticals in India (2019).