evidence: It is widely known that soda, beer and coffee are bad for your teeth. Bottled water, however, seems harmless. But dentists warn that is not always the case. Some of the most popular brands of bottled waters have dangerous pH levels and lack essential fluoride, which can cause cavities. However, it is impossible to know from the label which ones are the safest – so we tested the pH levels of nine top brands to see which ones were the best and worst. The pH level can range from zero to 14. On that scale, seven is neutral, anything under that is acidic and anything higher is alkaline. Our investigation found that samples of four of nine popular bottled water brands were very acidic. The brands – Smartwater, Dasani, Aquafina and Voss – had a pH level of 4. [...] We tested nine bottled water brands to see their pH levels. Brands with pH levels closer to zero are more acidic and can erode your tooth enamel. Brands with pH levels between seven and 14 are alkaline.