Rio Tietê pollution spurs massive cleanup plan in São Paulo

A dense white foam covered part of the Rio Tietê in Salto, São Paulo state, after heavy rains increased river flow. Cetesb attributed the foam to high pollutant loads and called for greater sanitation investment, noting that "as we have a large pollution load, it is essential to invest in sanitation". The agency aims to connect 1.5 million households to new sewage‑treatment lines by 2026, targeting a 20 % reduction in the river’s organic load.

A separate study by the Fundação SOS Mata Atlântica found the entire 1,100‑km course of the Tietê, from its source in Salesópolis to its mouth at the Paraná River, contaminated with microplastics, caffeine, heavy metals, 25 pesticides and medicines. Gustavo Veronesi said, "We always think the problem is only sewage, but this study shows it is much more complex." The study highlighted agricultural runoff, industrial discharges and aging infrastructure as key sources. In response, the São Paulo state government announced a R$23 billion investment program to clean the river system by 2029.