Do not eat at work. A lot of dirt? Or a lot of germs? If it is really dirty (germy) don't eat or drink at work. Make sure you wash your hands well before you eat or drink. A teacher once said, there is a difference between clean dirt and dirty dirt. A dusty place might look bad, but if you don't have breathing trouble, it won't likely harm you. Also being around a few germs helps make your immune system stronger.
Unsanitary? Is is possible for the workplace to be cleaner? If yes, discuss with your supervisors or Occupational health to look for solutions that would make the workplace better for everyone.