Scientists and manufacturers are urging Australians to re-wear T-shirts instead of washing them after one use in an effort to reduce the number of microplastics polluting waterways.

Research has found that more than 700,000 synthetic microplastics enter waterways from just one load of washing. Lead researcher Dr Mark Browne, a senior ecology lecturer at UNSW, said T-shirts naturally produced less odour and required less washing.

"Our whole emphasis is about giving information to the consumer": Dr Mark Browne at his washing machine lab in Manly Vale. Credit:Edwina Pickles

"Over 65 per cent of plastic that we find in marine habitats is made up of tiny fibres, and we wanted to know how widespread that was," he said. "We expected to find packaging and other things, but the fibres were the most abundant."

The research, which was conducted at a lab in Manly Vale, found that most of the microplastics in our waterways were acrylic, nylon and polyester. Last year, the micrometre-sized plastics were found in humans for the first time and were thought to be a result of consuming seafood.