Are bioplastics toxic?

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.