If furnaces and other devices that burn fuel are health hazards, then what are the affects of burning fuel on human health?

Answer choices:
- emissions
 - They aid lung health.
 - direct damage to the lungs
 - They are a hazard.
 - The affects are mildly healthy
 - The fuel burns clean.
 - Greenhouse gases
 - Global warming

 

    They are a hazard.      