1. Brakes of motor vehicles

2. Engines of motor vehicles

3. Microwave stoves within homes

4. Power plants

5. Telephone lines

Select the correct answer using the code given below

(a) 1, 2, 3 and 5 Only

(b) 1, 2 and 4 Only

(c) 3, 4 and 5 Only

(d) 1, 2, 3, 4 and 5

12. Ans: b

Explanation: 

Magnetite Particles:

• Magnetite are the biologically and anthropologically  formed nanoparticles of the strongly magnetic mineral.
• These particles can also originate from different sources, including fossil fuel combustion in motor vehicle emissions, lubricating oil, vehicle brake abrasion, abrasion and corrosion of vehicle engines, coal burning, and waste burning, iron impurities in burning fuel—especially diesel—and indoor sources such as printer toners, and leaky stoves.
• The use of coal for industrial applications such as coking in the production of steel and in power plants is indicated to be a major source of spherical magnetic combustion-associated magnetite fine particles and nanoparticle environmental pollution.
• These particles were first detected in the human brain over 20 years ago. Given their toxicity, abundance in roadside air, and nanoscale dimensions, traffic-derived magnetite pollution nanoparticles may constitute a chronic and pernicious neurotoxicant.
• As many of the airborne magnetite pollution particles are <200 nm in diameter, they can enter the brain directly through the olfactory nerve and by crossing the damaged olfactory unit. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. Therefore magnetite particles have been seen as contaminants in the environment.

Hence , option b is correct.

Read: Previous Year UPSC Environment Questions (PYQs) With Explanation 2021