In vitro study assesses hormonal activity of leachates from bio-based polymers used in food packaging; demonstrates integration of toxicity testing in packaging development can help reduce toxicity and design safer bio-based packaging
In an article published on September 20, 2022, in the journal Frontiers in Toxicology, Emma Harper and co-authors from Queen’s University Belfast, United Kingdom, analyzed the endocrine-disrupting properties and metabolic activity of leachates from bio-based polymers originating from several renewable resources.
Specifically, the scientists studied polymers extracted from biomass (thermoplastic starch); polymers produced using bio-derived monomers such as polybutylene succinate (PBS), polycaprolactone (PCL), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT) and blends thereof; or by the action of microorganisms (polyhydroxy butyrate). Inorganic waste additives (poultry litter ash and eggshell), conventional non-bio-based polypropylene (PP), and PP with mixtures of different additives were also included. Harper et al. performed overall migration experiments according to European standards (24 h and 10 days at 20 and 40 °C, water, and methanol). Subsequently, they applied the leachates to mammalian reporter gene assays measuring (ant)agonism of estrogen, androgen, and progestogen nuclear receptor transcriptional activity. They also performed the thiazolyl blue tetrazolium bromide (MTT) assay to monitor cytotoxic effects and assess metabolic activity.
The researchers reported that leachates of PLA, poultry feather-based polymer, poultry litter ash/PP (10:90), and eggshell/PP (40:60) induced estrogenic activity which was “within a range of 0.26–0.50 ng 17β-estradiol equivalents per ml.” The methanolic extract of poultry litter ash/PP (10:90) also induced anti-androgenic activity at 40 °C. None of the analyzed samples showed progestogenic effects. The methanolic extracts of eggshell/PP (0.1:99.9) and PP reduced the metabolic activity of the estrogen-responsive cell line as did the migrate of PP in water.
According to Harper and co-authors, “the major finding” was that changing formulations may help to reduce or eradicate a material’s toxic effects. For instance, the reduction of eggshell in PP/eggshell formulations reduced estrogenic activity compared to higher eggshell concentrations as did the blending of PLA with PBT compared to PLA alone. This demonstrates that performing toxicological analysis alongside the design of bio-based materials provides “a useful approach for safer packaging development.”
A previous study has shown that bio-based plastics are similarly toxic as conventional plastics (FPF reported) and a review discussed the pros and cons of bio-based plastics including toxicological aspects (FPF reported).