Magnetite particles are generated as a result of various human activities and are a form of environmental pollution. These particles are suspected to cause neurodegenerative problems, such as Alzheimer's disease. The sources of magnetite particles include:

1. Brakes of motor vehicles: When the brake pads of motor vehicles are applied, they produce a significant amount of dust. This dust contains magnetite particles that are released into the air and can be inhaled by people.

2. Engines of motor vehicles: The combustion of fuel in engines generates magnetite particles, which are emitted through the exhaust pipes of motor vehicles. These particles can enter the atmosphere and be inhaled by people.

3. Microwave stoves within homes: Microwave stoves do not generate magnetite particles as they do not involve combustion or friction.

4. Power plants: Power plants, particularly those that burn coal, generate magnetite particles as a result of the combustion process. These particles are emitted into the atmosphere and can be inhaled by people living in the surrounding areas.

5. Telephone lines: Telephone lines do not generate magnetite particles.

Therefore, the correct answer is 1, 2 and 4.