A mini review of the toxicity of Thallium (Tl) at low doses is herein presented. Thallium has severe toxicity. Although its acute biological effects have been widely investigated and are well known, its biological effects on human health and in cell cultures at low doses (<100 μg/L) due, for example, to Tl chronic exposure via consumption of contaminated water or foods, have often been overlooked or underestimated. Relatively few papers have been published on this topic and are herein reviewed to provide a focused scientific opinion in the light of current worldwide regulatory issues.

The origin of a resurgent hexavalent chromium contamination in groundwater from a phreatic aquifer in the Friuli Venezia Giulia Region plain was investigated by chromium isotopic systematics. The area underwent a severe Cr(VI) contamination by industrial effluents in 1997, when Cr(VI) concentration in groundwater reached 4500 µg/L. In subsequent years the contamination naturally attenuated, totally disappearing in 2003. A renewal of water contamination was observed in 2008, Cr(VI) reaching 1560 µg/L. The δ⁵³Cr value in groundwater and extracts from sediments was measured in 2009–2011, and it ranges between −3.21 and +0.21‰ and between −4.71 and +1.26‰, respectively. Due to the lack of geogenic Cr-sources, these data are interpreted as evidence of the subsequent oxidation through Mn-oxides of the Cr(III) hosted in the aquifer and originated by the reduction of the original industrial chromates. Cr(III) is characterized by negative δ⁵³Cr, starting from the δ⁵³Cr value around zero of Cr(VI) in industrial effluents. Oxidation liberates soluble Cr(VI) which is transported by groundwater and permeated soils. The complex Cr-isotopic vs. concentration distribution reflects both the new Cr(VI) reduction and dilution processes in the aquifer system. From an environmental point of view, the data raise concerns regarding the potential impact of past Cr(VI)-contamination.

This study deals with arsenic distribution in groundwater, soil and edible vegetables in the densely populated area of the Versilia Plain (Tuscany region, Italy), addressing potential impacts on people’s health. The data revealed high As concentrations in some domestic irrigation wells, exceeding 1200 µg/L. The average As concentration in topsoil and subsoil was 39 and 46 mg/kg, respectively, with the highest concentration reaching about 200 mg/kg. Arsenic concentrates in plant roots compared with the edible parts; in tomato fruits, black cabbage leaves and edible leek parts As reached about 0.2 mg/kg, 0.4 mg/kg and 3 mg/kg, respectively. Geochemical and hydrostratigraphic data suggest that As in soils and alluvial sediments originated from mineralized and historical upstream mining areas. The exposure routes for both non-carcinogenic and carcinogenic risk assessment here considered include soil ingestion, dermal absorption, soil dust inhalation and vegetable consumption. For non-carcinogenic and carcinogenic effects, the hazard was higher than the acceptance threshold. The calculated soil screening levels resulted even lower than the guideline soil-concentration imposed by Italian regulations, and this poses an issue on the actual meaning of arsenic regulatory thresholds.