Assessing the pollution and ecotoxicological status of the Igua?u River, southern Brazil: A review

The degradation of water resources available for human consumption is increasing with the continuous release of chemicals into aquatic environments and their inefficient removal in wastewater treatment. Several watersheds in Brazil, such as the Iguacu River, are affected by multiple sources of pollution and lack information about their pollution status. The Iguacu River basin (IRB) has great socioeconomic and environmental relevance to both the supply of water resources and its considerable hydroelectric potential, as well as for the high rate of endemism of its ichthyofauna. Also, the IRB is home to large conservation units, such as the Iguacu National Park, recognized by UNESCO as a natural World Heritage Site. Thus, this article discusses the chemical pollution in the IRB approaching: (i) the main sources of pollution; (ii) the occurrence of inorganic and organic micropollutants; (iii) the available ecotoxicological data; and (iv) the socioeconomic impacts in three regions of the upper, middle, and lower IRB. Different studies have reported relevant levels of emerging contaminants, persistent organic pollutants, toxic metals, and polycyclic aromatic hydrocarbons detected in the water and sediment samples, especially in the upper IRB region, associated with domestic and industrial effluents. Additionally, significant concentrations of pesticides and toxic metals were also detected in the lower IRB, revealing that agricultural practices are also relevant sources of chemicals for this watershed. More recently, studies indicated an association between fish pathologies and the detection of micropollutants in the water and sediments in the IRB. The identification of the main sources of pollutants, associated with the distribution of hazardous chemicals in the IRB, and their potential effects on the biota, as described in this review, represent an important strategy to support water management by public authorities for reducing risks to the local endemic biodiversity and exposed human populations. Integr Environ Assess Manag 2024;00:1-26. (c) 2023 SETAC Multiple pollution sources affect the water quality of the Iguacu River basin, which exhibits the highest levels of contamination in the upper region resulting from the intense industrial and urban wastewater, which lacks proper treatment plant systems.Despite the decreasing levels of both inorganic and organic contaminants along the main river course, other diverse sources of pollution, such as crops and livestock, continue to release chemicals, especially pesticides, affecting the water quality downstream.The high rate of endemism of the ichthyofauna from the Iguacu River, highlighting its ecological relevance, may be explained by its limnological features associated with the construction of six cascading hydropower reservoirs along the river.Considering the great socioeconomic (water use for consumption) and environmental relevance (biodiversity and high rate of endemism) of the Iguacu River, the pollution of this aquatic environment represents an issue of great public concern because it threatens significant ecological and health risks.