Wallace advised swimmers to remain cautious when swimming in Pangbourne Meadow.
“The River Pang suffers from very high levels of pollution and if there’s been a discharge (there) in the last few days that might affect people’s health,” he said.
“You have to be careful and check there hasn’t been any sewage discharge on the day or soon before and you should be fine but there will always be a baseline level of pollution.
“My advice would be to keep your head out of the water and don’t go in it if you have any open wounds,” he added.