i have to say circulation. the circulation in your left hand is better than in your right.
i am sure that if you could bottle the country air and take it with you into the city and not have to breathe one cc of that polluted air you would do so without question. its the same thing with water. its that basic. its that important.
usually the left side is worse than the right(that i am privy to), so perhaps you have reversed any blockage in the left side and have a ways to go to get the right side. perhaps distilled water will make the difference. i love my distiller, and its a cheap sears model.