Water fluoridation
Health and dental organizations worldwide have endorsed its safety and effectiveness. Its use began in 1945, following studies of children in a region where higher levels of fluoride occur naturally in the water. Further research showed that moderate fluoridation prevents tooth decay.
Olafur Eliasson
In 1998, Olafur discovered that uranin, a readily available nontoxic powder used to trace leaks in plumbing systems, could dye entire rivers a sickly fluorescent green. Olafur conducted a test run in the Spree River during the 1998 Berlin Biennale, scattering a handful of powder from a bridge near Museum Island. He began introducing the environmentally safe dye to rivers in Moss, Norway (1998), Bremen (1998), Los Angeles (1999), Stockholm (2000) and Tokyo (2001) — always without advance warning.