Mercury in italian bottled water: ultra-trace determination and evaluation of intake using a health risk assessment approach

Mercury (Hg) is a widespread toxic element and a persistent pollutant with adverse health effects on humans and biota. Hg is released from natural sources and/or processes, and human activities, that are responsible for its presence in all environmental matrices (air, water and soil). Thus, Hg can enter and accumulate in the food chain causing harmful effects on human health depending on its chemical form (elemental mercury, inorganic mercury and organic mercury), route, dose and duration of exposure. The most toxic organo-mercurial compound found frequently in the environment is methyl-mercury (Me-Hg) taken by eating fish, shellfish and fish-derived products through diet. Drinking water is a minor source of mercury (as inorganic, mainly Hg2+) exposure. A total of 244 bottled waters representing 164 different brands and 136 Italian springs were analysed. For the first-time, mercury was found in a large population of Italian natural mineral waters (in bottled waters coming from 18 Italian regions) in the range of sub-nanogram to a few nanograms per litre, well below the National and European regulatory limit established at 1 ?g L-1. Differences in HgT concentrations were related not only to the environmental characteristics of the springs but also to the extent and impact of human activities. Higher concentrations were found in bottled waters coming from regions with former mining and/or natural thermal and volcanic activity (Tuscany and Campania). In addition, through the laboratory results obtained, it was possible to carry out a risk evaluation of exposure to mercury from bottled water for three age groups of consumers (adults, child and toddlers). The mean mercury daily intake was found to be remarkably lower, not only than the provisional tolerable value (1 ?g L-1 according to European and Italian legislation) but also than the estimated provisional tolerable weekly intake (PTWI) value (4 ?g kg-1 body weight) recommended by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Based on this dataset, daily and weekly exposure assessments were calculated, the resulting estimated weekly intake (EWI) together with the hazard quotient (HQ) with respect to the reference dose for mercury (RfD) were very low. This shows that there is little or no risk for mercury consumption from Italian bottled waters at the present time.