The mystery of how hormone-disrupting chemicals have come to be found in lakes and rivers has been solved, and the culprit is the washing machine.

Scientists have long puzzled as to how flame retardant compounds and chemicals used to make plastics bendy end up in the environment as factories are careful not to allow spillages.

The levels of phthalates and retardants in the natural world is worrying because there is increasing evidence that they damage fertility and could be the reason why male sperm counts have fallen dramatically since the 1940s.

Women with the highest concentrations of phthalates in their bodies are also more likely to suffer low libido and a study published this week by British researchers showed that the fertility of dogs has dropped since 1988,  because they share the same environment to humans.

Now researchers at the University of Toronto believe they have found the answer to how they chemicals are polluting the natural world.

It appears that human clothing can trap the chemicals in their fibres and come laundry day, they are released into water of the washing machine, before being swept away into the sewerage system.

Wastewater plants extract less than 20 per cent of the chemicals so most will find their way into rivers and lakes.

“These results have implications regarding the role of clothing conveying chemicals with indoor sources to the outdoor environment,” said lead author Dr Miriam Diamond, from the Department of Physical and Environmental Sciences at Toronto.

“Our results suggest that physical and chemical properties of fabrics, as well as chemicals, account for chemical accumulation and release

“Clothing is unique in the indoor environment as it undergoes continual laundering.  These results support the hypothesis that clothing acts as an efficient conveyer of (chemicals) from indoors to outdoors through accumulation from air and then release during laundering.”