Urinary iodine, fluorine, and arsenic levels and goiter prevalence of school-age children exposed to water-source environment with high iodine, high fluorine, and high arsenic concentrations

Background  The imbalanced distribution of iodine, fluorine, and arsenic in nature causes biogeochemical diseases in some rural areas of China.

Objective  This study investigates the physical development status of school-age children in areas with high iodine, high fluorine, and high arsenic in drinking water, explores the relationships among urinary iodine, urinary fluorine, and urinary arsenic, and analyzes the influencing factors of goiter in this group.

Methods  Using cluster sampling, 208 children aged from 8 to 12 years (101 males and 107 females) were selected from three villages in Qingxu County, Shanxi Province. The height and weight of the children were measured on the spot. Thyroid volume and nodules were examined by ultrasound. Meanwhile, random urine samples were collected during the day for the detection of urinary iodine, fluorine, and arsenic levels.

Results  In the selected school-age children, the median urinary iodine, fluorine, and arsenic levels were 541.85 μg·L^-1, 1.82 mg·L^-1, and 0.11mg·L^-1, respectively. The mean height, weight, and body mass index (BMI) were 145.74 cm, 35.95kg, and 16.50 kg·m^-2, respectively. Except urinary iodine (H_{urinary iodine}=9.11, P_{urinary iodine}=0.06), there were significant differences in urinary fluorine and arsenic levels among different age groups (H_{urinary fluorine}=10.97, P_{urinary fluorine}=0.03; H_{urinary arsenic}=11.12, P_{urinary arsenic}=0.03). Based on the partial correlation analysis adjusting for age, there were positive correlations between urinary iodine and urinary fluorine (r=0.44, P < 0.001), between urinary iodine and urinary arsenic (r=0.32, P < 0.001), and between urinary fluorine and urinary arsenic (r=0.40, P < 0.001). The positive rate of goiter was 10.58% in total participants, and the positive rate of goiter in each age stratum of the children aged 8 to 12 years was 13.33%, 8.33%, 14.70%, 19.05%, and 3.84%, respectively (χ²=8.47, P=0.06). The thyroid ultrasound results showed that the goiters were mainly diffuse type (9.13%) and mixed type (1.44%), and there was no simple nodule type. In the multivariate logistic regression analysis, large BMI (OR=1.17, 95%CI:1.03-1.33) and high urinary fluorine level (OR=2.67, 95% CI:1.72-4.14) were risk factors for positive goiter detection.

Conclusion  The positive rate of goiter is high in the study areas with high iodine, high fluorine, and high arsenic in drinking water. Types of goiter are mainly diffuse type and mixed type. The physical development of the school-age children aged from 8 to 12 years is basically normal. There are positive correlations among urinary iodine, urinary fluorine, and urinary arsenic. Large BMI and high urinary fluorine level are suspected risk factors for goiter.