Iodine was discovered by the French chemist Bernard Courtois in 1811 and later defined as an element by Joseph Louis Gay-Lussac and Humphrey Davy acting separately in 1813. In the mid-19th century, French scientists realised the connection between iodine deficiency and goitre but it was David Marine in Ohio and David Murray Cowie in Michigan who popularised the use of iodised salt in the 1910s and 1920s. Iodisation of table salt has become compulsory in many countries but notable exceptions include the UK, USA and, until …