Iodine concentration in common potable water sources in the estates of Ratnapura district and thyroid status of children

Abstract

INTRODUCTION: Iodine deficiency is the single most important cause of hypothyroidism. Drinking water is an important source of iodine for humans. Objective: To identify the common potable water sources available to the estate population in the Ratnapura District, to determine the iodine concentrations in different water sources and to ascertain the relationship between water iodine concentrations and thyroid status of children 5 to 9 years of age. METHOD: A descriptive cross sectional study was carried out in three phases in 20 randomly selected estates in the Ratnapura district of Sri Lanka from September to November 2009. In phase 1, 1,683 households in the selected estates were surveyed to identify the drinking water sources. In phase 2, blood samples from 519 randomly selected children aged 5-9 years from the same estates were taken to assay TSH levels after obtaining informed written consent from parents. In phase 3, water samples from 23 identified sources (wells, rivers and springs) were analysed for iodine levels by the catalytic reduction method. Water sources were grouped on elevation above mean sea level. The mean TSH levels and water iodine concentrations were correlated. RESULTS: The main source of drinking water was spring water (83.7%). Spring water at low altitudes had significantly higher iodine concentrations than that located at higher altitudes (p<0.01). The mean iodine concentration in spring water was significantly lower than that in other sources (p<0.001). There was no association between the mean TSH levels of children and the altitudes at which they lived (p>0.05). There was no significant association between TSH levels of children and iodine concentration in drinking water (p>0.05). CONCLUSIONS: The main potable water source available to the population in the Ratnapura District was spring water (84%). The mean iodine concentration of spring water was significantly lower as compared to other water sources. There was no significant association between serum TSH levels in children 5 to 9 years of age and iodine concentration in drinking water.