Peculiarities of disorders in physical development of children consuming drinking water with increased nitrate content

Abstract

Peculiarities of physical development disorders in 334 children were examined in the course of comparative clinical-laboratory research; all these children consumed drinking water with various nitrates content (11.2±1.1 mg/l and up to 3.14 MPC, i.e. 141 mg/l), in a dose equal up to 9.0 mg/kg of body weight (RfD 1.6 mg/kg). A focus group consisted of 158 children aged from 3 to 10, a control group was made up of 176 children of the same age. Nitrates content in urine taken from children of focus group (49.22±11.69 mg/l) was 2.4 fold higher than the same parameter in control group (20.2±3.13 mg/l, р=0,001). Under exposure to nitrates consumed with drinking water endocrine system diseases were detected 1.7-2.1 fold more frequently, and physical development disorders, 2.5-4.3 fold more frequently, than in control group (р=0.02-0.05). We detected authentic correlation between nitrate excretion with urine and deviations in physical development in children consuming drinking water with nitrogenous compounds content which was higher than MPC; such deviations were ICD: Е44-Е46 - mild protein-energy malnutrition, Е34.4 - excessive height, Е67.8-Е66.0 - excessive nutrition, ОR=2.35, DI=1.22-4.53). Explained variance fraction amounted to 42-75% (R2=0.42-0.75; 64.9≤F≤162.3, р=0.001). Changes in thyroid gland volume were detected 2.4 fold more frequently, and changes in its structure 2.5 fold more frequently, in focus group than in control group (р=0.049). We determined statistically significant correlation between thyroidal disorders and nitrate content in urine (ОR=3.52; DI=1.73-7,0), with factor contribution level reaching 52% (R2=0.52; F=173.3; р=0.001). We detected that 34% of children from focus group had thyrotrophic hormone level 1.2 fold higher than physiological standard and the same parameter in control group (р=0.02). And also free thyroxin level was near age physiological standard in 23.4% of examined children which was 1.2 fold lower than in control group (p=0.05). The research revealed that methemoglobinemia with tissue respiration abnormalities and disorders in liver enzyme system functioning followed by protein-energy malnutrition (ICD: E44.1-E46), were the most relevant for younger children (under 6 years) and children suffering from functional gastrointestinal pathologies. As for older children (6-10 years) we observed mostly disorders in neuroendocrine regulation, thyroid gland, and antioxidant protection, in them together with somatic development potentiation and growth in weight-height parameters (ICD: Е66.0-Е67.8). It has been established that reduced thyroid supply, disorder of tissue respiration and antioxidant balance, and dysregulation of hypophysial-adrenal homeostasis section provide the basis for the formation of disturbances in physical development and endocrine pathology in children being under oral exposure to nitrates.