Period 6 element devices though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favor of alcohol-filled, galinstan-filled, digital, or thermistor-based instruments. It remains in use in scientific research applications and in amalgam material for dental restoration. It is used in lighting: electricity passed through mercury vapor in a phosphor tube produces short-wave ultraviolet light which then causes the phosphor to fluoresce, making visible light. Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray other metal resembles tin but discolors when exposed to air. The
Ship disposal examples of where environmental concerns have complicated the planned disposal of ships have been the Norwegian Cruise Lines vessels SS "Norway" and SS "Oceanic", as well as the French aircraft carrier "Clemenceau". Although in the past there were few effective controls on ship disposal, and the risk of being caught was therefore limited, national authorities as well as environmental organisations are now more vigilant. Ships are sometimes tracked when they are nearing the end of their lifespan. Companies caught disposing of ships illegally face hefty fines. Ship disposal A number of different methods exist for disposing of a ship after