Anthropogenic activities performed in the Ecuadorian Amazon have released potentially toxic elements (PTEs) into the rivers, causing severe environmental pollution and increasing the risk of exposure to the residents of the surrounding areas. This study aims to carry out a human health risk assessment using deterministic and probabilistic methods to estimate the hazard index (HI) and total cancer risk (TCR) related to multi-pathway human exposure to PTEs in polluted rivers. Concentrations of Al, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in surface water and sediment samples from rivers on the Ecuadorian Amazon were considered to assess the potential adverse human health effects. As a result, deterministic and probabilistic estimations of cancer and non-cancer risk through exposure to surface waters and sediments were above the safety limit. A sensitivity analysis identified the concentration of PTEs and the exposure duration (ED) as the two most important variables for probabilistic health risk assessment. The highest risk for receptors was related to exposure to polluted sediments through incidental ingestion and dermal contact routes. According to the deterministic estimation, the human health risk through ingestion of water was above the threshold in specific locations. This study reveals the potential health risk to which the population is exposed. This information can be used as a baseline to develop public strategies to reduce anthropogenic pollution and exposure to PTEs in Ecuadorian Amazon rivers.

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Artisanal and small scale gold mining operations have been an important source of toxic elements in the environment, with possibly negative consequences for ecosystems and human health. This study aims to assess the pollution degree and human health risk due to heavy metals exposure in mining communities. The data correspond to samples collected in rivers located in the vicinity of Ponce Enríquez, one of the most important gold mining sites in Ecuador. The concentrations of As, Cd, Cu, Pb, and Zn were analysed in surface water (n = 13) and sediment (n = 7) samples. Heavy metals contents were compared with (a) the corresponding backgrounds values (Bi) and (b) the permissible limits established by the Ecuadorian regulation. Furthermore, the Geo-accumulation Index (Igeo) and Metal Index (MI) were estimated for sediments and surface waters, respectively. Lastly, the potential adverse effects on human health due to the exposure to HMs in polluted rivers were carried out based on the hazard index (HI) and total cancer risk (TCR), using the traditional deterministic approach. The results showed that surface waters and sediments were enriched in heavy metals. The 57% of the sediment samples showed severe to extremely pollution (Igeo > 3) due to the high contents of As and Cd. On the other hand, surface water was in the strongly to seriously affected category (MI > 3) in 23% of the sample's locations, with As, Cu and Pb as the main contaminants. Likewise, residents exposed to polluted rivers showed HI and TCR values above the safe exposure threshold (HI = 1 and TCR = 10 5 ), being as the main contributor to the overall risk. Based on the preliminary results found in this research, future rivers monitoring and control efforts are needed to reduce the pollutions levels and the health hazard of the inhabitants of the mining areas.