Carbonated water contains carbon dioxide(CO2). This carbonic acid is more acidic than regular water, somewhere in the range of apple and orange juice.
While sparkling mineral waters show slightly greater erosive potential than still waters, it's about one hundred times less than soft drinks (pop/soda/Coke/Pepsi).
Not all carbonated/sparkling waters are the same--they tend to have different mineral content, so if you need to watch your sodium intake, for instance, read the labels carefully.
Long-term drinking of pop can do untold damage to your health--erosion of teeth and bones by phosphoric acid is the least of your concerns, as other ingredients include carcinogens derived when you digest the artificial sweetener and neurotoxin, aspartame, and the preservative potassium benzoate.
In contrast, the only real health concern with drinking carbonated water is aggravation of irritable bowel syndrome (IBS) from the release of CO2 which can cause bloating and gas. However, some people with simple indigestion actually benefit from the increased burping caused by carbonated water.