when did they start putting iodine in salt
Iodised salt In the U.S. in the early 20th century, goitre was especially prevalent in the region around the Great Lakes and the Pacific Northwest.[24] David Murray Cowie, a professor of paediatrics at the University of Michigan, led the U.S. to adopt the Swiss practice of adding sodium iodide or potassium iodide to table and cooking salt. On May 1, 1924, iodised salt was sold commercially in Michigan.[25] By the fall of 1924, Morton Salt Company began distributing iodised salt nationally. There was a gradual increase in average intelligence of 1 standard deviation, 15 points, in iodine-deficient areas and 3.5 points nationally.[26]
Khewra Salt Mine The Khewra Salt Mine (or Mayo Salt Mine) is located in Khewra, north of Pind Dadan Khan,[1] an administrative subdivision of Jhelum District, Punjab Region, Pakistan, which rises from the Indo-Gangetic Plain.[2] It is Pakistan's largest, the world's 2nd largestâ€Š[3] and the oldest salt mine in the world.[4][5][6] It is a major tourist attraction, drawing up to 250,000 visitors a year.[7] Its history dates back to its discovery by Alexander's troops in 320 BC, but it started trading in the Mughal era.[8] The main tunnel at ground level was developed by Dr. H. Warth, a mining engineer, in 1872 during British rule. After independence, the Pakistan Mineral Development Corporation took over the mine, which still remains the largest source of salt in the country, producing more than 350,000 tons per annum[9] of about 99% pure halite.[7] Estimates of the reserves of salt in the mine vary from 82 million tons[10] to 600 million tons.[11]