Iodine status and goitre prevalence in nitrate-exposed schoolchildren living in rural Bulgaria.

Nitrate and perchlorate are well-known water pollutants that are harmful to human health. They may inhibit the accumulation of iodide in the thyroid gland. The present study investigated iodine status and goitre prevalence in schoolchildren aged 7-14 years from two villages in Bulgaria with high and low levels of nitrate, and negligible levels of perchlorate in drinking water. Comparison between the mean and median urinary iodine concentrations of the exposed and non-exposed children showed a statistically significant difference for the boys. A statistically significant difference was also found for goitre prevalence between the exposed and non-exposed children. The relative risk for schoolchildren exposed to a high level of nitrate in drinking water, expressed as an odds ratio, was 3.014 (95% confidence intervals 1.293-7.027; P=0.0105) and this was considered to be significant. This study confirmed that a high level of nitrate in drinking water is a risk factor for thyroid dysfunction in this population.