Sewage sludge used to fertilise Australia’s farmlands is loaded with microplastic and is getting into the food chain, researchers warn.
Scientists have taken a forensic look at the sludge left over when wastewater is treated at plants across the nation.
The nutrient-rich waste product is called biosolids and most of the 349,000 tonnes produced each year is spread on agricultural land.
But 146 samples from 13 treatment plants in NSW, South Australia and Queensland reveal it contains worrying levels of microplastic – fibres and fragments so small they’re usually invisible to the naked eye.
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Biosolids were found to contain between 1 and 17 kilograms of microplastic per tonne.
“We found every kilogram of biosolid contains between 11,000 and 150,000 microplastic particles,” says Griffith University’s Dr Shima Ziajahromi, who led the study.
Fibres from synthetic clothing was the dominant type of microplastic found and abundances were notably higher during cold and wet seasons, probably because people are washing more items such as fleece blankets and clothes.
Ziajahromi warns that without quick action, including mandatory microplastic filters on washing machines, the nation risks entrenching long-term contamination problems in food production hubs.
“Australian regulations control the amount of heavy metals, nutrients, pathogens and some emerging contaminants that are allowed in biosolids,” she said. “But there’s currently no guideline for microplastics concentrations.”
AAP