http://www.lef.org/magazine/mag2009/oct2009_Halt-on-Salt-Sparks-Iodine-Deficiency_01.htm
The public health message to limit salt use underlies a gradual and insidious return of iodine deficiency. The National Health and Nutrition Examination Surveys (NHANES) assessment of Americans’ health revealed a 50% reduction in iodine levels and a quadrupling of iodine deficiency in the period between 1971 and 1994. Twelve percent of the population surveyed from 1988 to 1994 were severely iodine deficient, judged by urinary levels of iodine.8 Women of childbearing age are at particular risk for iodine deficiency, with up to 36% evidencing low levels.9
A recent detailed analysis of several brands of commercially available salt showed that, after opening, iodine is lost rapidly from the product. Once the container is exposed to air, iodine content is nearly gone within four weeks after opening (even faster under conditions of high humidity). The study suggests that, even among people who use the salt shaker frequently for cooking and food, daily iodine intake may be below the recommended daily intake.10
The majority of salt used in processed foods is not iodized. While dairy products and baked foods (bread and related products) were formerly substantial sources of iodine, the iodine content of these foods has dropped due to changing practices by dairy producers and bakers.10-12
Thanks, now I’m glad I read this thread thoroughly.