Salt
The amount of iodine and the specific iodine compound added to salt varies from country to country. In the United States, the Food and Drug Administration (FDA) recommends [21 CFR 101.9 (c)(8)(iv)] 150 micrograms of iodine per day for both men and women. US iodized salt contains 46–77 ppm (parts per million), whereas in the UK the iodine content of iodized salt is recommended to be 10–22 ppm.
Kombu
"Kombu" contains extremely high levels of iodine. While this mineral is essential for normal growth and development, the levels in kombu can cause overdoses; it has been blamed for thyroid problems after drinking large amounts of soy milk in which "kombu" was an additive.