Peculiarities of chemical composition of drinking water in rural settlements of Bryansk region and evaluation of its health effect (contribution to endemic thyroid diseases)

Chemical composition of drinking water samples (n=515 in total) collected in rural settlements of Bryansk region (Russia) in the period from 2007 to 2020 was analyzed to reveal its relation to the origin of water-bearing rocks and spatial distribution of endemic diseases of thyroid gland among local population. To identify the health effects of drinking water, spatial correlation between concentrations of iodine, selenium and other elements in particular settlements and medical information on the prevalence of endemic thyroid diseases among the local residents was assessed. Sampling was carried out in rural settlements distributed within all the 27 districts of the Bryansk region from different available sources fed by aquifers in hydrogeological structures of different composition and age. Water samples were analyzed for major cationogenic elements (Ca, Mg, Sr, K, Na, Mn, Zn, Fe, Al, Si) and anions (HCO₃^2-, Cl^-, F^-, SO₄^2-, NO₃^2-, PO₄^2-)as well as for I^- and Se using ICP-AES, potentiometry, photometry and spectrofluorimetry.

The results confirmed a low supply of water samples with iodine (Me= 5.96 μg/L, variation range 0.06 - 41.2 μg/L) and selenium (Me= 0.18 μg/L, variation 0.001 - 6.21 μg/L). The concentration levels of iron (64% of examined districts), manganese (36% of examined districts) and strontium (8% of examined districts) appeared to be inconsistent with hygienic standards. Tendencies of relationship between water iodine concentration and the incidence of thyroid diseases caused by iodine deficiency among teenagers aged 8 to 12 have been found. The same trend was found when comparing geochemical data with iodine content in renal excretion in this age group.

The presented study demonstrates the applicability of spatial data analysis in identifying and visualizing the relationship between the manifestation of endemic thyroid diseases and the geochemical characteristics of the environment, which is necessary for assessing the quality of local diets and their correction.

The study was partly supported by Russian Foundation for Basic Research and Belorussian Republican Foundation for Basic Research (project number 20-55-00012).