# Water contamination on São Paulo coast

> Live situation record from CLSTR: https://clstr.news/situations/water-contamination-on-so-paulo-coast
> Updated: 2026-09-30T18:27:00.000Z. Sources: 16. Developments: 3.

Water quality issues along the São Paulo coast have escalated significantly. Initially, the environmental agency Cetesb classified 16 beaches in the Baixada Santista region as unfit for swimming, with the city of Santos being particularly affected. During this period, authorities also issued weather alerts for storms and sea swells.

By mid-September, the scale of contamination expanded across the state, with 116 beaches classified as improper for bathing. The Baixada Santista region remains the most heavily impacted area with 63 improper locations, followed by the North Coast with 50. In Baixada Santista, only nine beaches maintained a “green flag status,” including locations in Bertioga, Guarujá, and Peruíbe. Officials attribute the widespread poor water quality to heavy rainfall, which increases the risk of sewage contamination. Health authorities have warned that the contaminated water poses risks of gastroenteritis.

Recent assessments via the Coastal Water Quality Index (IQAC) highlight significant pollution involving fecal matter, organic matter, and nutrients. In the Baixada Santista region, eight of 11 monitored coastal areas were classified as regular, poor, or terrible. Specifically, the São Vicente and Piaçaguera channels were classified as “terrible,” while the Santos Channel deteriorated from “regular” to “poor.” Some areas showed improvement, such as the Itaguaré River and the Guarujá Outfall, which moved to a “good” classification. To address these sanitation challenges, approximately R$ 10.6 billion in investments are planned for the region through 2029, with R$ 8.2 billion earmarked for water supply and sewage systems across nine municipalities.

## Timeline

### 2026-09-30: Cetesb reports poor water quality in Baixada Santista coastal areas

Cetesb reports that eight of 11 coastal areas in Baixada Santista, Brazil, have regular to terrible water quality due to pollution, prompting planned sanitation investments of R$ 10.6 billion by 2029.

4 sources. https://clstr.news/cluster/cetesb-reports-poor-water-quality-in-baixada-santista-coastal-areas

### 2026-09-17: São Paulo coast sees 116 beaches unfit for bathing

Over 100 beaches along the São Paulo coast, particularly in Baixada Santista, are unfit for swimming due to contamination following heavy rains, according to Cetesb.

6 sources. https://clstr.news/cluster/so-paulo-coast-sees-116-beaches-unfit-for-bathing

### 2026-09-03: Baixada Santista beaches face contamination and weather alerts

Cetesb reports 16 unfit beaches in Baixada Santista, with Santos facing high contamination levels, while local authorities issue weather alerts for storms and sea swells.

8 sources. https://clstr.news/cluster/baixada-santista-beaches-face-contamination-and-weather-alerts

---
Cite as: Water contamination on São Paulo coast. CLSTR, https://clstr.news/situations/water-contamination-on-so-paulo-coast