Compostable food packaging may contaminate compost
US research flags presence of potentially hazardous substances leaching from takeaway containers. Andrew Masterson reports.
Compostable food containers might not be the environmental boon they appear to be, with a study finding that substances used in their manufacture can degrade and leach – with thus far unknown consequences.
Researchers led by Youn Jeong Choi of Purdue University in Indiana, US, found that per- and polyfluoroalkyl substances (PFAS), used as oil- and water-repellents in the making of the containers, transform into perfluoroalkyl acids (PFAAs) inside large-scale composters.
PFAAs have been shown to migrate from commercial fertilisers into humans.
The PFAS used in container manufacture are classified as short-chain varieties, and little is known about the potential effects of their ingestion by humans.
Long-chain PFAS – particularly perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) – have been linked to poor health outcomes, including increased cholesterol and lower fertility.
As a result, US companies have phased out production and shifted to the short-chain varieties. Little research regarding their health impacts has so far been conducted.
The research of Choi and colleagues, thus, brings no evidence related to any particular health concern, but provides a brute measure of the degree to which perfluoroalkyl acids persist through commercial composting processes.
To make their findings, the researchers tested 10 samples, drawn from facilities in five US states. Seven of the samples were drawn from large-scale composting plants that used the food containers in their mix. Two were from operations that excluded the containers, and one was from a backyard compost bin.
All of the samples contained perfluoroalkyl acids, but levels were much higher in those derived from composts that included food containers. Most of the PFAAs were directly attributable to the degradation of short-chain PFAS, although all samples also contained smaller amounts of the long-chains types – reflecting their continued use in some other countries.
Although health impacts for short-chain PFAS have yet to be fully defined, some states in the US have opted for pre-emptive regulation. Washington, for instance, has legislated to ban them in the use of paper food packaging from 2022.
The research is published in the journal Environmental Science & Technology Letters.