The Swiss Federal Institute of Aquatic Science and Technology, ETH Zurich and The University of IL conducted the investigation. The researchers also conducted controlled groups of new bath toys under conditions simulating household use over 11 weeks.
The study by the Swiss Federal Institute of Aquatic Science and Technology, ETH Zurich and the University of IL, counted microbes swimming inside the yellow toys and found the murky liquid released when ducks were squeezed contained "potentially pathogenic bacteria" in four out of the five toys studied.
Scientific curiosity knows no bounds: a group of Swiss and U.S. researchers have delved into "the dark side" of inviting rubber ducks and other flexible plastic toys into our tubs.
When they cut open the toys, "the findings sound unappetising: between five million and 75 million cells per square centimetre were observed on the inner surfaces", according to the summary of the report. The ducks had two strains of bacteria often seen in hospital acquired infections. They arise from the polymers within the plastic material that provide the nutrients that these microbes need to grow and multiply. She says that they found that it was the chemical carbon structure that the toys were made of that provided growth material for the bacteria. Among the exposed users: Children "who may enjoy squirting water from bath toys into their faces, " a statement from the institute said.
Bodily fluids like urine and sweat, along with soap and personal care products in bathwater, allows nutrients like nitrogen and phosphorus to develop, creating a thriving haven for bacteria.
In some cases, they say exposing children to microbes like this can result in a stronger immune system.
The study concluded that it was the "low-quality polymer" [synthetic materials used as plastics] in the plastic rubber ducks that fostered the growth of bacteria, not necessarily the water in it. The Swiss government isn't making any recommendations at this stage.