Speciated and Total Urinary Arsenic Levels in Belo Horizonte, the Largest Brazilian City within the Mineral-Rich Region “Iron Quadrangle”

Abstract

The “Quadrilátero Ferrífero” (Iron Quadrangle) is a mineral-rich province in Brazil, where arsenic anomalies are associated with gold mining and tailings dam failures. Urine samples were randomly collected from residents of Belo Horizonte (BH) city (N = 506 total/138 speciation) and the metropolitan area (N = 35 total/10 speciation), with stratifications in age, female-male and geopolitical regions. Creatinine, acid-digested total arsenic (TAs), and five inorganic and organic arsenic species were measured: arsenobetaine (AsB); arsenous (AsIII) and arsenic (AsV) acids and their dissociation products; monomethylarsonic acid (MMA); and dimethylarsinic acid DMA). Overall, the TAs GM (μg/g creat) of all stratification groups indicated no statistical difference. The TAs geometric mean (GM) of BH was 9.68 [9.17–10.2] μg/g creat, being AsB (43.8%) and DMA (20.7%) the major components. The toxic arsenic (ToxAs) fraction (i.e., AsIII + AsV + MMA + DMA) was 5.23 [4.45–6.15] μg/L. These TAs and ToxAs values are lower than international benchmarks and the Brazilian legislated standard of 35 μg/L for ToxAs. The TAs GM (μg/L) and creatinine were 36% higher for males than for females (p < 0.0001), making TAs GMs comparable, after creatinine correction. Similarly, though the 10–19 age group showed significantly higher ToxAs GM (12.7 [6.49–24.8] μg/L) (p = 0.048) and creatinine (p < 0.001), the ToxAs GM (7.22 [2.92–17.9] μg/g creat), was not statistically different than those from the other age groups. The study, the first one in Brazil, identifies the relative contribution of inorganic and organic arsenic and provides a baseline level for clinical reference and bio-monitoring studies, particularly applicable to both occupational and non-occupational populations in a mineral-rich region. Graphical abstract