Overview
- The Environment Agency confirmed on Wednesday that a blue‑green algal bloom has been found at the Ham and Kingston bathing site and warned people not to swim in that stretch of the Thames.
- The EA has activated an advice‑against‑bathing notice on SwimInfo, put officers back on the river to take more samples, and told the UK Health Security Agency and downstream abstractors to expect test results.
- Local councils have installed warning signage and urged people to keep dogs and children out of the water because cyanobacteria can produce toxins that cause skin rashes, sickness if swallowed, and can kill animals.
- The Ham and Kingston stretch was officially designated as a bathing water on May 15 but remains unclassified for water quality while the EA completes sampling for a classification due after the season ends on September 30.
- Campaigners have linked the bloom to sewage and nutrient runoff, pointing to a May EA inspection that found permit breaches at the nearby Hogsmill treatment works, a development that could increase pressure for stricter wastewater standards and affect planned river projects.