The S.O.S. Mata Atlântica Foundation has conducted a study indicating a significant deterioration in the water quality of rivers in 14 states across Brazil. The findings highlight alarming trends, especially in the Trapicheiro River, which flows from Tijuca National Park into Guanabara Bay. Despite appearing visually clean, the water quality tests conducted over the year showed a troubling decline in critical indicators of water quality.

Bruno Waldman, a volunteer from S.O.S. Mata Atlântica, pointed out that there has been a decrease in water volume along with a slight degradation in water quality. The study involved continuous monthly sampling of 128 rivers throughout 2025, which revealed that the average water quality has worsened compared to the previous year. The research found that the number of locations with 'good' water quality plummeted from nine in 2024 to merely three in 2025, with only the Betume River in Sergipe and two rivers in São Paulo, namely Piraí and Água Limpa, meeting acceptable standards.

These findings raise profound concerns about the ecological health of Brazil’s water bodies and signal potential risks to both human populations and biodiversity. The decline in water quality could have severe implications for public health, local ecosystems, and the overall sustainability of water resources, emphasizing the need for urgent conservation efforts and enhanced environmental management practices in the region.