DIETARY IODINE INTAKE FROM DRINKING WATER IN DENMARK

Iodine is an essential nutrient and adequate intake levels are of paramount importance for public heath as iodine influences thyroid function and both high and low iodine intake levels are associated with increased risk of disease in a population. Iodine deficiency disorders (IDD) are hence a recognized public health problem world-wide. In Denmark a mandatory salt fortification program (iodized table salt and salt for bread production, 13 ppm) was accordingly initiated in 2000 to combat this issue. Prior to the iodization ca. 25% of the iodine in the average Danish diet came from drinking water and other beverages. A recent study (published in 2010) on the dietary habits in Denmark showed that drinking water incl. other beverages is now on a 4^th position after milk and milk products, bread and cereal, and spices (incl. iodized salt) representing 14% of the daily iodine dietary intake. These high percentages of iodine intake from drinking water, both before and after the salt fortification have been explained by the groundwater origin of the drinking water in Denmark. However, existing studies, based on very few drinking water sampling locations (in total 55), revealed that iodine concentration in Danish drinking water varies from 0.7 μg l^-1 to 140 μg l^-1.

We’ll here present a Danish nation-wide project aiming at 1) elucidating the spatial variability of iodine speciation and concentration in drinking water, and consequently, 2) estimating the effect on the dietary iodine intake from drinking water depending on the water abstraction area. Notes on the comprehensive design of a national sampling campaign aiming at studying the iodine speciation in the drinking water and the effect on the dietary iodine intake will be given with special focus on the representativity and the factors influencing it. In addition, preliminary results on iodine speciation from two pilot study sites (both in Denmark) and the variability of iodine contents in groundwater on different scales will also be presented as high and low iodine concentrations in tap water even on a local scale may influence the health of sub-populations.