Enrichment of potentially toxic elements in brazilian coal and ash: Risks to human health

Coal combustion remains an important energy source in Brazil, particularly in the southern region, where the country's largest coal reserves are located. However, the disposal of coal and ash residues raises environmental and public health concerns due to the accumulation of potentially toxic elements (PTE). This study investigates the chemical and mineralogical composition of coal, fly ash, and bottom ash from the Candiota (RS) and Figueira (PR) power stations, focusing on PTE enrichment and the associated human health risks. Elemental and mineral compositions were determined using ED-XRF and XRD, respectively. Human health risks were assessed through the Hazard Index (HI) and Carcinogenic Risk (CR). High PTE concentrations were identified in both coal and ash samples, with notably elevated mean levels of As (579.26 mg kg⁻¹), Cr (198.47 mg kg⁻¹), and Pb (154.11 mg kg⁻¹). Ashes exhibited significant enrichment ratios of As, Sr, Zn, and Pb (1.52 - 24.26), especially in the fly fraction. Quartz was the predominant mineral phase, while hematite and anhydrite were also detected in ash samples. The HI indicated potential non-carcinogenic effects from As, Cd, Pb, and Cr, mainly for children (HI = 0.10 - 48.96), whereas CR values for As, Cd, and Cr through ingestion (2.32E-04 - 2.20E-02 for children; 1.05E-04 -2.36E-03 for adults) exceeded recommended safety thresholds. These findings highlight the need for improved management of coal combustion residues to mitigate human exposure and health risks in coal-based energy production areas.