Vacations are supposed to leave you feeling relaxed, happy, and healthy -- but if you travel by air, you might feel worse by the time you get home than you did when you left. Fear of flying? For good reason. Flying should not generally be the transportation option of choice for the environmentally minded, given its intensive use of resources. (Intercity buses consume less than a fifth the energy jets do to cover the same amount of distance.) And not only is it lousy for the Earth, it's not great for your own health, either. Returning to the U.S. recently …