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Bioplastics: a clean alternative?

Are bioplastics toxic?

Pure research James Bowers, Chief editor at Polytechnique Insights
On February 2nd, 2021 |
3 mins reading time
4
Are bioplastics toxic?
Lisa Zimmermann
Lisa Zimmermann
PhD student in biology at Goethe University
Key takeaways
  • In 2019, biologist Lisa Zimmermann published findings which indicate that 67% of consumer items made of petroleum-based plastics contain chemicals with at least some level of toxicity.
  • Her most recent study found that 67% of the 43 bioplastic and plant-based products she tested contained chemicals that demonstrate ‘baseline toxicity’.
  • Lisa concludes that toxicity of bioplastics and plant-based materials matches that of conventional petroleum-based plastics.

As a con­sumer walk­ing down the super­mar­ket aisles, it is easy to see two very sim­i­lar look­ing types of pack­ag­ing and auto­mat­i­cal­ly assume that they are made from the same mate­r­i­al. But even two dif­fer­ent types of bio­plas­tic prod­ucts which may look the same can dras­ti­cal­ly vary in composition. 

Lisa Zim­mer­mann (Goethe Uni­ver­si­ty) stud­ies tox­i­c­i­ty in every­day plas­tic prod­ucts. A PhD researcher in the Plas­tX research group at the ISOE in Frank­furt, she con­sid­ers bio­plas­tics as alter­na­tives with poten­tial, “bio­plas­tics do have advan­tages. Biobased plas­tics can be pro­duced using renew­able resources and oth­er bio­plas­tics can be biodegrad­able – even if there are issues with biodegrad­abil­i­ty.” But she does warn that even if they could be bet­ter from an envi­ron­men­tal per­spec­tive, this is not always the case. And it also does not nec­es­sar­i­ly mean they are bet­ter from a tox­i­co­log­i­cal one. 

Last year, she pub­lished research show­ing that 67% of the 30 petro­le­um-based plas­tic con­sumer items she test­ed con­tained chem­i­cals with at least some lev­el of tox­i­c­i­ty 1. In addi­tion, she test­ed four items that were made from the sec­ond most com­mon bio­plas­tic, poly­lac­tic acid (PLA) – includ­ing a yoghurt cup and veg­etable tray. All four also had what the authors referred to as ‘high base­line tox­i­c­i­ty’, an indi­ca­tor that the prod­ucts con­tain chem­i­cals capa­ble of dis­rupt­ing the nat­ur­al func­tion­ing of bac­te­ria in a petri-dish (or in vitro). 

In her lat­est study pub­lished in Envi­ron­ment Inter­na­tion­al, Lisa Zim­mer­mann and her co-authors went fur­ther 2. They acquired 43 dif­fer­ent con­sumer prod­ucts made of sev­er­al types of bio-based and biodegrad­able mate­r­i­al – PLA, PHA, PBS, Bio-PE, Bio-PET, Starch and Cel­lu­lose. Her results showed that the same pro­por­tion (67%) as for the petro­le­um-based plas­tics analysed in the pre­vi­ous study induced in vit­ro tox­i­c­i­ty, thus indi­cat­ing that just as many bio­plas­tics can con­tain chem­i­cals sim­i­lar to those in tra­di­tion­al plastics. 

“This was a screen­ing of a diverse set of prod­ucts to see if they con­tain chem­i­cals that are poten­tial­ly harm­ful. It is still too ear­ly to say how they might affect human health,” she states. But it is known that some chem­i­cals used in plas­tics can dis­rupt hor­mone func­tion­ing (known as endocrine dis­rup­tion) and increase can­cer risk, amongst oth­er health issues. 

To bet­ter under­stand the tox­i­c­i­ty, future stud­ies using food or water are need­ed to see how the chem­i­cals migrate from the plas­tic under real-world con­di­tions. “What our study shows, how­ev­er, is that each plas­tic prod­uct on shelves, has an indi­vid­ual chem­i­cal com­po­si­tion and tox­i­c­i­ty. We see that some prod­ucts are safer by design than others.”

How­ev­er, com­pa­nies pro­duc­ing plas­tic have their own for­mu­la­tions, which are pro­tect­ed as intel­lec­tu­al prop­er­ty mean­ing the exact com­po­si­tions are not read­i­ly avail­able. Lisa Zim­mer­mann calls for more trans­paren­cy. “If plas­tic for­mu­la­tions were more trans­par­ent, it would be very help­ful for design­ing safer prod­ucts. Some of the prod­ucts we test­ed con­tained >1,000 chem­i­cal fea­tures and a lot of the chem­i­cals are unknown. You can’t test the tox­i­c­i­ty of some­thing you don’t know is there.”

She also points out that cur­rent safe­ty assess­ment of food con­tact mate­ri­als only test tox­i­c­i­ty of the indi­vid­ual start­ing mate­ri­als. “This means they don’t test for inter­ac­tions between two or more of these chem­i­cals togeth­er. If you don’t test the mix­tures con­tained in the end prod­uct, one sub­stance that might not be harm­ful on its own could be tox­ic when in a mix­ture with others.”

Fur­ther­more, tox­ic end points are usu­al­ly not includ­ed in cur­rent life cycle assess­ments of prod­ucts used to deter­mine the eco­log­i­cal foot­print of a prod­uct. This means that, for the moment, envi­ron­men­tal ben­e­fits are tak­en into con­sid­er­a­tion more than safe­ty aspects relat­ed to chem­i­cal tox­i­c­i­ty of prod­ucts. Lisa Zim­mer­mann calls for more con­sid­er­a­tion of chem­i­cal safe­ty when design­ing tru­ly “bet­ter” plas­tic alternatives. 

1https://​pubs​.acs​.org/​d​o​i​/​1​0​.​1​0​2​1​/​a​c​s​.​e​s​t​.​9​b​02293
2https://​pubmed​.ncbi​.nlm​.nih​.gov/​3​2​9​5​1901/