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?

The correct option is 2 and 3.

Let us analyze each statement step-by-step to understand why this option is correct:

Statement 1: Other than those made by humans, nanoparticles do not exist in nature.
This statement is incorrect. Nanoparticles exist widely in nature. Natural sources of nanoparticles include volcanic ash, ocean spray, dust storms, forest fires, and even biological processes (such as certain proteins and viruses). Therefore, nanoparticles are not exclusively man-made.

Statement 2: Nanoparticles of some metallic oxides are used in the manufacture of some cosmetics.
This statement is correct. Nanoparticles of metallic oxides, such as titanium dioxide (TiO₂) and zinc oxide (ZnO), are extensively used in commercial cosmetics, particularly in sunscreens. Because of their tiny size, they provide effective ultraviolet (UV) light protection while remaining transparent on the skin.

Statement 3: Nanoparticles of some commercial products which enter the environment are unsafe for humans.
This statement is correct. When nanoparticles from commercial products enter the soil, water systems, or air, they can accumulate in food chains. Due to their small size and high surface-area-to-volume ratio, they can easily penetrate biological membranes and cells, potentially causing toxic, inflammatory, or carcinogenic effects in humans and other organisms.

Since statements 2 and 3 are correct, and statement 1 is incorrect, the correct option is indeed 2 and 3.