title: Humic substances in drinking water and the epidemiology of thyroid disease.
abstract: Thyroid diseases are common in all populations but the type and frequency depends on environmental factors. In Denmark geographical differences in iodine intake are caused by different iodine contents of drinking water, which varies from < 1 to 139 microg iodine per litre. Comparative epidemiologic studies have demonstrated considerable differences in type and occurrence of thyroid disease with more goitre and hyperthyroidism in Aalborg with water iodine content around 5 microg/L, and more hypothyroidism in Copenhagen with water iodine around 20 microg/L. In Denmark, iodine in ground water is bound in humic substances, which have probably leached from marine sediments in the aquifers. Interestingly, humic substances in water from other parts of the world have goitrogenic properties, especially humic substances from coal and shale. Humic substances are heterogeneous mixtures of naturally occurring molecules, produced by decomposition of plant and animal tissues. The effect of humic substances in drinking water on the epidemiology of thyroid disease probably depends on the source of aquifer sediments.
authors.affiliation: Department of Endocrinology and Medicine, University Hospital Aalborg, Denmark. laurberg@aas.nja.dk
authors.forename: Peter
authors.initials: P
authors.lastname: Laurberg
authors.forename: Stig
authors.initials: S
authors.lastname: Andersen
authors.forename: Inge Bülow
authors.initials: IB
authors.lastname: Pedersen
authors.forename: Lars
authors.initials: L
authors.lastname: Ovesen
authors.forename: Nils
authors.initials: N
authors.lastname: Knudsen
mesh_terms: D002614:Chelating Agents / Q000009:adverse effects / Q000032:analysis; D003718:Denmark / Q000453:epidemiology; D005618:Fresh Water / Q000737:chemistry*; D006801:Humans; D006812:Humic Substances / Q000009:adverse effects* / Q000032:analysis; D007455:Iodine / Q000008:administration & dosage / Q000032:analysis / Q000652:urine; D013959:Thyroid Diseases / Q000139:chemically induced / Q000453:epidemiology*; D014881:Water Supply / Q000032:analysis
chemical_list: D002614:Chelating Agents; D006812:Humic Substances; D007455:Iodine