Correct Answer: (b) 1, 2 and 4 only
Solution:Magnetite is an oxide formed by iron ions of valences 2+ and 3+. Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 25 years ago. These brain magnetites display compelling similarity with the magnetite nanospheres formed by combustion, which are ubiquitous and prolific in urban, airborne particulate matter (PM). Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior. Magnetite could be toxic to the brain, generating harmful reactive oxygen species that have been linked to Alzheimer’s disease. In addition to occupational settings (including, for example, exposure to printer toner powders), higher concentrations of magnetite pollution nanoparticles are likely to arise from open fires and vehicles (tailpipe and brake wear) and/or industrial (power plants) PM sources. There is no clear evidence of the generation of magnetic particles from microwave stoves within homes or from telephone lines. Hence, option (b) is the correct answer.