Thyroid Threat

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October 30, 2006

Thyroid Threat: Increased iodine supplementation not a solution

After the CDC study was published, some observers suggested that it would be cheaper and easier to increase iodine intake in the general population to alleviate perchlorate-related health issues than to clean up contaminated drinking water supplies. Although EWG supports consideration of iodization of salt and other foods as a partial preventive measure for hypothyroid conditions in the population, it is not an effective solution to the problem of perchlorate contamination of drinking water and should not be used as a justification to allow what would otherwise be unacceptably high levels of perchlorate exposure, as would occur under the current proposal for a standard of 6 ppb perchlorate in tap water.

First, iodine supplementation is difficult to control in terms of how much iodine an individual gets. Iodine fortification of food was actually reduced in the US, for example, in the 1980's because of concerns that excess iodine intake could cause autoimmune thyroid disease and thyroid cancer. [26, 28] Increased iodization of salt would also be limited in effectiveness because some individuals must limit their salt intake due to high blood pressure, kidney disease, or other health issues, and because infants do not eat solid food to which iodized salt could be added.

It is also important to point out that even with modern public health practices, some degree of nutrient deficits are essentially impossible to avoid in the general population. The extra sensitivities of these individuals must be considered &em; especially when this population extends to more than one-third of all women. Finally, it is simply not ethical to ask the population to increase their iodized salt intake simply to counteract the effects of a chemical contaminant in their bodies.


While California and other states should be commended for moving forward to set standards for perchlorate in drinking water given the federal government's failure to do so, it would be unwise to finalize these standards until the results of the CDC study are amply taken into consideration. With the CDC study showing that even less than 1 ppb perchlorate in water may pose health risks to women, fully protective drinking water standards must be set as low as possible &em; at no more than 1 ppb &em; and revised downward as detection and cleanup technology improves.