Preliminary assessment of potentially toxic elements in soil, sediment, blood, and urine, and their possible relationship with thyroid dysfunctions in southern region in a metropolitan area of Mexico.

This preliminary, exploratory study assessed the concentrations of eight potentially toxic elements (As, Cd, Cr, Cu, Ni, Se, Pb, and Zn) in soil, sediment, blood, and urine samples collected in the southern region of the Metropolitan Zone of the Valley of Toluca (MZVT), Mexico, and examined their possible association with thyroid pathologies. PTEs were quantified by inductively coupled plasma mass spectrometry (ICP-MS); Pearson correlation coefficients and independent samples t-tests (p < 0.05) were applied to explore associations between matrices and to compare PTEs concentrations between individuals with previously diagnosed thyroid pathology (TG, n = 10) and those without prior disease (NonTG, n = 12). Mean concentrations of As, Cd, Pb, and Se in soils and sediments exceeded the natural geological background values of the Earth's crust. Blood and urine analyses revealed elevated systemic burdens of Pb, Cr, Ni, and Cd; for contextual reference, concentrations in some participants exceeded both U.S. general population reference values and biological exposure indices established for occupationally exposed personnel, a comparison intended to illustrate the magnitude of the observed burden rather than to imply occupational exposure. No statistically significant differences in PTEs concentrations were found between the TG and NonTG subgroups for any evaluated element. Within this exploratory cohort of 22 voluntary participants, 10 had a previously diagnosed thyroid condition; this proportion reflects solely the composition of the study sample. These preliminary findings highlight the need for larger, longitudinal, and biochemically controlled epidemiological studies to evaluate the potential public health implications of PTEs exposure in the region.