The rupture of the Brumadinho mining tailings dam in Brazil is considered one of the largest mining disasters in the world, resulting in 244 deaths and 26 missing people, in addition to the environmental consequences. The present study aims to evaluate the concentrations of multiple elements and the biological effects on water and sediments of the Paraopeba River after the Brumadinho Dam rupture. The tailings are formed by fine particulate material with large amounts of Fe, Al, Mn, Ti, rare earth metals and toxic metals. In the water, the levels of Fe, Al, Mn, Zn, Cu, Pb, Cd and U were higher than those allowed by Brazilian legislation. In the sediments, Cr, Ni, Cu and Cd levels were higher than the established sediment quality guidelines (TEL-NOAA). The differences in metal concentrations in the water and sediments between the upstream and downstream sides of the dam illustrate the effect of the tailings in the Paraopeba River. Toxicological tests demonstrated that the water and sediments were toxic to different trophic levels, from algae to microcrustaceans and fish. The fish exposed to water and sediments containing mine ore also accumulated metals in muscle tissue. This evaluation emphasizes the necessity of long-term monitoring in the affected area. In less than four years, two major environmental tragedies involving mining dams occurred in Brazil. The first incident is considered the industrial disaster with the greatest environmental impacts in Brazilian history and the largest of the world involving tailings dams. The rupture of the Fundão Dam in the subdistrict of Bento Rodrigues, 35 km from the municipality of Mariana in Minas Gerais State on November 5, 2015, resulted in 19 deaths due to the release of more than 40 million m 3 of tailings that were transported to the mouth of the Doce River 1. The 668 km length of affected water by Fundão tailings is the largest ever recorded 2. The second incident occurred on January 25, 2019, when a tailings dam ("Dam B1") failed at Córrego do Feijão mine in the city of Brumadinho, also in Minas Gerais State, releasing approximately 12 million m 3 , which directly affected the administrative area of the company and parts of the nearby communities 3 , resulting in 244 deaths and 26 missing people, as some bodies were completely buried in the mud and never found 4. Although the previous evaluation by the Brazilian Mining Agency classified Dam B1 in Brumadinho as "low risk of collapse and high potential of associated damage" 5 , the rupture of the Brumadinho Dam led to the release of iron ore tailings into the Feijão stream that is a tributary of the Paraopeba River 6 (Supplementary Video, Fig. 1). Along the way, the volume of tailings led to an immediate increase in water turbidity (Supplementary Fig. S1a), impacts on the water supply in the municipalities provided by the Paraopeba River, and damage to fauna and
