Comparison of ultra-low levels of total mercury in tap waters and bottled mineral waters in a region of southern Italy (Calabria)

In recent years numerous papers on the determination and speciation of mercury (Hg) in environmental matrix have been published. These studies are particularly relevant to evaluate the impact of mercury on ecosystems and human health due to its neurotoxicity and teratogenic effect. Detection of mercury at ultra-trace concentrations is a challenging task, that requires clean lab facilities, accurate sampling procedures and analytical methods having very low quantification limit for Hg. In this study, the potential impact of mercury in drinking water in the Calabria region, has been evaluated. To reach this goal 81 water samples between drinking (tap water, TW) and bottled natural mineral waters (BW), scattered throughout the Calabria region, were considered for assessment and comparison of their total mercury (HgT) content. A total of 60 TW samples were collected from public drinking fountains and private houses/public places, supplied by municipal pipelines, over five provinces of Calabria. Commercially available still and sparkling bottled waters (n=21), randomly selected, were purchased from a supermarket and commercial activities (bars, restaurants and hotels). Sampling of TW was performed following the strict criteria suggested in USEPA method 1669. Both TW and BW were analyzed using cold-vapor atomic fluorescence spectrometry (CVAFS) following USEPA Method 1631. Levels of this toxic element in all samples, ranging from sub- to few nanogram per litre, were found well below the European and Italian regulatory limits set at 1 ?g /L for both typologies. Concentrations of HgT in BW (LOQ-0.91 ng/L) resulted largely lower than those found in TW (0.14-5.57 ng/L). Indeed, for 81% of BW we detected HgT between LOQ (<0.09 ng/L) and 0.30 ng/L, whereas only for 20% of TW we had Hg at or below 0.30 ng/L. Considering the whole dataset, we evaluated HgT results between TW and BW, and between still and sparkling waters. Total mercury levels of these two typologies of drinkable water may be attributable to the fact that TW and BW undergo or do not undergo physical/chemical treatment processes and originate from differences sources.