Heavy metal(loid)s contamination in water and sediments in a mining area in Ecuador: a comprehensive assessment for drinking water quality and human health risk

Elevated heavy metal(loid)s concentrations in water lower its quality posing a threat to consumers. This study aims to assess the human health risk caused by heavy metal(loid)s in tap water in Santa Rosa city, Ecuador, and the ecological risk of stream water and sediments in the Santa Rosa River. Concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn were evaluated in tap waters, stream waters, and sediment samples during the rainy and dry seasons. The Metal Index (MI), Geo-accumulation Index (Igeo), Potential Ecological Risk Index (PERI), and the levels of carcinogenic (CR) and non-carcinogenic risk (HQ) were determined. The results revealed severe pollution levels, mainly in Los Gringos and El Panteon streams, both tributaries of the Santa Rosa River, the primary water source for Santa Rosa inhabitants. More than 20% of the surface water samples showed severe contamination (MI > 6), and 90% of the tap water samples presented a MI value between 1 and 4, which indicates slight to moderate pollution. Drinking water displayed high levels of As, with 83% of the tap water samples collected from households in the dry season above the recommended concentration set by the World Health Organization and Ecuadorian legislation. The Igeo-Cd in the sediment samples was significantly high (Igeo > 3), and the PERI showed very high ecological risk (PERI > 600), with Cd as the main pollutant. HQ and CR were above the safe exposure threshold, suggesting that residents are at risk from tap water consumption, with As being the primary concern.