Addition of chlorine during water purification reduces iodine content of drinking water and contributes to iodine deficiency.

Drinking water is the major natural source of iodine in many European countries. In the present study, we examined possible sites of iodine loss during the usual water purification process.Water samples from 6 sites during the technological process were taken and analyzed for iodine content. Under laboratory circumstances, prepared iodine in water solution has been used as a model to test the effect of the presence of chlorine. Samples from the purification sites revealed that in the presence of chlorine there is a progressive loss of iodine from the water. In the chlorine concentrations employed in the purification process, 24-h chlorine exposure eliminated more than 50% of iodine when the initial iodine concentration was 250 µg/l or less. Iodine was completely eliminated if the starting concentration was 16 µg/l.We conclude that chlorine used during water purification may be a major contributor to iodine deficiency in European communities.