Biodegradable bewilderment? Paper cups can be as toxic as plastic, find Swedish researchers

31 Aug 2023 --- Swedish researchers have found that single-use paper cups could be as toxic to environmental and human health as plastic. The team left both types of packaging in wet sediment and water for several weeks and followed how leaching chemicals affected midge larvae.

PP cups, PS lids and paper cups lined with polylactic acid (PLA) were put under conditions representative of plastic leaching in the environment.

Toxicity was tested in contaminated water and sediment separately. The study authors assessed the aquatic invertebrate Chironomus riparius at multiple endpoints in larval stages and emergence to the adult phase.

They observed a significant growth inhibition with all the materials tested when the larvae were exposed to contaminated sediment. Developmental delays were also observed for all materials in both environments.

The researchers tested paper and plastic impacts on midge larvae.Dr. Bethanie Carney Almroth, professor of ecotoxicology and environmental science at the department of biological and environmental sciences, University of Gothenburg, Sweden, tells Packaging Insights that the findings show labels like “biodegradability” are often misleading.

“There is a degree of confusion about the terms bioplastic, bio-based plastic and biodegradable plastic, which are sometimes interchangeable but have different meanings,” she says.

Bioplastics confusions
Most plastics are produced from fossil fuels, but a small percentage are made from renewable resources like corn or sugar cane. These bio-based plastics can be used to create more rapid biodegradation (such as PLA) or to produce slower degrading plastics (like PP).

But materials like PLA, which can be used as a barrier layer for paper, usually require special conditions, such as industrial composters, to speed up the degradation process.

“Very few plastics will actually biodegrade in a home compost. Consumers might mistakenly assume that bio-based plastics are ‘natural,’ safe and easily degradable. Additionally, I think very few people are aware of the extensive use of chemicals in plastics products, including those of PLA,” says Carney Almroth.

The study results showed teratogenic (congenital) effects via the analysis of mouthpart deformities in chironomid larvae and found significant effects on larvae exposed to PS lid leachates in sediment. Also, a significant delay in time to emergence was observed for females exposed to paper cup leachates in sediment.

Detoxing paper, researching further
Carney Almroth says that finding a solution to ensure paper can be disposed of safely in the environment is difficult.

Substances like PFAS have traditionally been used to render paper more fat and water-resistant, but these have well-documented health and environmental effects, and bans are partly in place while more are being discussed, she notes.

Other replacements would also need to be adequately vetted to prove their safety before uptake onto the market. Adequate toxicity testing must be performed on all new packaging materials, say the researchers.

“This should, of course, include toxicity testing but also other aspects of sustainability like climate impacts, length of time the material remains valuable in the market, land and water usage, circularity and end of life waste management,” continues Carney Almroth.

“In general, extraction of resources, and the linear economy it supports, needs to be reduced. Current and predicted production volumes of chemicals and plastics outpace our ability to mitigate harm, resulting in planetary-scale harm and moving us outside the safe operating space for humanity. This includes the make-use-waste practices inherent to single-use products.”

The study shows that the toxicity of the tested products speaks to a broader need to understand chemicals in products and their potential fate and impacts, she asserts.

“There are currently very few regulations on the 13,000 chemicals used in plastics production and products. I am, together with colleagues around the world, calling for increased requirements for transparency and reporting throughout the plastics value chain.”

“Future research needs to address the multiple aspects of materials production, use and circularity. This should be done using a systems perspective to ensure that our new choices are truly [environmentally] sustainable, and the new circular economy is truly restorative and regenerative,” she says.

“We should avoid regrettable substitutions, situations in which we solve one problem and replace it with another.”

By Louis Gore-Langton

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