Researchers at the University of Toronto's Faculty of Applied Science & Engineering have observed that handwashing synthetic fabrics in water with higher total dissolved solids (TDS) leads to more microplastic fibres (MPF) being released.
The study, published in Scientific Reports , investigated how polyester fabrics fared when handwashed in various types of water. Although some fabrics had a silicone-based coating meant to reduce MPF, the researchers found the coating's efficacy varied under different conditions.
The research holds implications for billions of people around the world without access to washing machines and soft water.
"Nearly two-thirds of the world does not have access to a washing machine," says lead author Amanuel Goliad, a master's student in the Durable Repellent Engineered Advanced Materials (DREAM) lab led by Associate Professor Kevin Golovin of the department of mechanical and industrial engineering.
Goliad, whose family is from Ethiopia, grew up knowing about handwashing's prevalence - and realized there was a gap in the research. "Most people around the globe handwash, yet nearly all the microfibre research focuses on machine laundering in high-resource settings," he says.
Synthetic fibres like polyester, nylon and acrylic - mainly used in fast fashion - account for some 69 per cent of textile production, according to the Changing Markets Foundation .
When such fabrics are laundered, the resulting friction results in MPFs being released into waterways.
Microplastics are notoriously difficult to remove from water. While the impacts to human health are unclear, microplastics are a known risk to marine life as they can block digestive tracts and cause injury when swallowed.
The DREAM lab had previously created a silicone-based coating to reduce friction in the laundering process and prevent the fibres from breaking off - but the coating was only tested with machine laundering fabrics.
For this study, Goliad adapted a bamboo washboard-based method from another research paper (he notes there's so little research on handwashing that finding a standardized method was difficult).
He then washed green and black polyester fabrics, both coated and uncoated, using de-ionized, tap and lake water from Lake Ontario. He then filtered the wash water to count and analyze the MPFs.
Under the microscope, Goliad found that significant amounts of MPFs were released. He also found that coating didn't prevent MPF release as much as was shown in previous research that used washing machines.
In green polyester fabric, coating reduced fibre shedding by about 92 per cent in deionized water but only 37 per cent in water from Lake Ontario, illustrating how its efficacy declines as TDS increases.
"The biggest impact in the efficacy of the coating comes from the type of wash water," says Golovin. "Most people that handwash clothing use whatever body of water is locally available; it could be a river, an ocean, a lake.
"There are more total dissolved solids within them, and that affects the release of these microfibres more than people realize."
At the same time, most research is being conducted in labs using deionized water, which has a TDS of 0, meaning that studies don't reflect the real washing conditions of much of the world.
"There are additional implications for communities that don't have access to laundry machines. They're the ones being exposed to more microfibres, but the policies and standards don't reflect this," says Golovin. "A potential action item resulting from this research - and hopefully, follow-up research - is that those communities might need better water filtration systems than what global policy is stipulating, because they're exposed to more MPFs."
Another surprising find in the study were the actual lengths of the fibres.
"Higher TDS levels resulted in shorter fibre lengths," says Goliad. "That's important because shorter fibres are harder to filter out in filtration systems; they spread more quickly and they're more easily ingested by aquatic life."
The researchers hypothesize that dissolved minerals in harder water may be breaking fibres into smaller pieces, with the DREAM lab now conducting research into fabric coatings that can better withstand handwashing in water with higher TDS.
"I hope this work highlights the environmental impact of hand washing and the need for more inclusive research," says Goliad.
This research was supported by the Canada Foundation for Innovation and the Natural Sciences & Engineering Research Council.
