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
The Broads practices and sewage disposal in the 1950s and 1960s released high levels of phosphorus and nitrogen into the Broads, causing eutrophication. Algal blooms can be toxic, posing a health risk to humans and wildlife. Mass decay of plant matter removes oxygen, damaging fish stocks, preventing recreational fishing. The loss of larger plants and reed fringes in eutrophic waters increases erosion of banks and the buildup of sediment on lake floors. This impedes navigation and requires costly dredging to remove. The beauty of the area is damaged by eutrophication, which is detrimental to the tourism industry. The Broads authority and Environment