Bioplastics may be toxic to soil organisms, study calls for more testing

By Douglas Main

Bioplastics, often considered a safer alternative to synthetic plastics, may in some cases be toxic to soil organisms, a worrisome finding that indicates a need for more thorough testing, according to a new study.

The work adds to a growing body of research suggesting that bioplastics, which are derived from plant materials or other biological feedstocks, are not necessarily safer than plastics that come from petroleum.

The new study, published this month in Environmental Science and Technology, found that two types of bioplastic fibers were more toxic to earthworms than were bits of conventional polyester. While promoted as “environmentally friendly,” the alternative materials actually may be more harmful in some ways than the conventional plastic, the study determined.

“We need more comprehensive testing of these materials before they are used as alternatives to plastics,” said Bangor University researcher Winnie Courtene-Jones, who is lead author of the study.

Bio-based fibers like viscose and lyocell are used in clothing, especially in fast fashion, but also in wet wipes and a range of other products. The study said more than 320,000 metric tons were produced in the textile industry in 2022 and that is expected to continue to climb. When such clothes are washed, they can shed fibers into wastewater. Thousands of tons of sewage sludge are added to farmlands around the world, which can directly transmit such fibers into the soil.

The study authors said they exposed worms to fibers from polyester, as well as viscose and lyocell, which are made from cellulose and used in “natural” fabrics. They found that after three days, 30% of the first group died, while the death toll was 60% for viscose, and 80% for lyocell.