- Emerging research shows that plant-based plastics — just like petroleum-based plastics — contain many thousands of synthetic chemicals, with large numbers of them extremely toxic. However, the bioplastics industry strongly denies that bio-based plastics contain hazardous substances.
- Scientists are finding that while plant sources for bioplastics, such as corn or cane sugar, may not themselves be toxic or have adverse health impacts, the chemical processes to manufacture bioplastics and the many performance additives needed to give them their attributes (hardness, flexibility, color, etc.) can be quite toxic.
- Those doing the research no longer see bioplastics as a solution to the global plastic pollution crisis and would like to see them regulated. However, a very large number of petroleum-based plastics and the chemicals they contain also lack tough government oversight.
- This week, representatives from the world’s nations gather for a fourth session to hammer out an international treaty to curb the global plastic pollution crisis. The High Ambition Coalition (including 65 countries) hopes to achieve a binding global ban on the worst toxins in plastics. But the U.S., China and other nations are resisting.
Almost 25 years after their hopeful debut, bioplastics contribute only about 1% of the global plastics market share, mainly for food packaging. But that may soon change.
The Biden administration announced an initiative in 2023 to “spur a circular economy” with the goal of replacing 90% of petrochemical-sourced plastics with bio-based materials over the next 20 years. With looming European mandates also aimed at addressing the plastic pollution crisis, analysts expect the bioplastics market to grow to 5 million metric tons by 2025.
At first glance this sounds like a good thing, but is it?
Motivated by the aggressive marketing of bioplastics as a solution to the plastic crisis, scientists are now peering inside these material innovations, and those doing the research don’t like what they see.
“Most people don’t know about toxins in plastics, period. And even people that do work with plastics don’t know about toxins in bioplastics,” says Bethanie Almroth, a professor of ecotoxicology and environmental science at the University of Gothenburg, Sweden, who has studied bioplastics.
These plant-based materials can be just as toxic as petroleum-based ones, she says. That’s not necessarily due to the plant world sourcing of base materials, but because of the chemical processes needed to make bioplastics and the additives required to achieve the many desirable qualities demanded of them (durability, flexibility, color, etc.).
In a 2020 study, researchers purchased bio-based plastic products such as food wrappers, food storage bags, reusable coffee cups, tea bags, disposable cutlery and coffee capsules. They also obtained raw materials (bio-based plastic pellets) at a plastics trade fair.
In the multipart study, the scientists first analyzed the pellet samples and found a complex mixture of thousands of chemicals, most of them unidentifiable. Next, the researchers exposed bacteria to extracts of the bioplastics; they found that the majority had multiple toxic effects.
And it didn’t seem to matter what type of bioplastic material was sampled when it came to toxicity: Bio-PET, polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polylactic acid (PLA) and polyhydroxyalkanoates (PHA) all contained similar numbers of chemicals with similar toxic effects. The biggest difference was that the consumer products tended to be more toxic than the pellets.
For a 2023 study published in Environmental Pollution, Almroth and her team placed plastic and paper cups lined with the bioplastic PLA in sediment and freshwater for up to four weeks. Then they added the contaminated water to a tank with mosquito larvae. The larvae exposed to the leachate from PLA-lined cups saw just as much mortality, inhibited growth and deformities as those exposed to petrochemical-based polystyrene and polypropylene.
These results don’t bode well for people drinking and eating out of bioplastic foodware, though toxicity effects on humans were not evaluated in the study, and more research needs to be done to back up the findings of these two early studies.
A plastic panacea or more of the same?
Bioplastics, a term that includes both bio-based plastics and biodegradable plastics, first came on the market in the early 2000s. Their growth has been slow, likely due to poor performance and a high price compared with regular plastic. Brands are also wary of adopting them at scale, fearing that cultivating sufficient agricultural inputs, like beets, corn, potatoes, and cane sugar, could lead to excessive land use and biodiversity loss — potentially raising red flags with consumers, environmentalists and governments. Plus, consumers are confused about whether and where to recycle or compost disposable bioplastic products.
Intuitively, it seems like a plastic made from corn instead of petroleum should contain fewer toxic chemicals. Unfortunately for people and wildlife, according to researchers, the only difference between bio-PET and PET is where the carbon to make the polymer comes from: plants or petroleum.
This differently sourced carbon, when processed and turned into plastic, comprises the same synthetic chemicals — the catalysts used to react and bond the chemicals to make bioplastics are the same or even stronger, while the performance additives to make them flexible, soft, colored, stretchy and more are also similar. In addition, both types of plastics can contain accidental contaminants, while bio-based plastics may include pesticide contaminants.
So, when you’re standing in front of a shelf full of disposable petroleum-based and bio-based foodware like cups and cutlery, which should you choose?
“From a toxicological perspective, my answer is quite simple: It doesn’t make any difference if you buy conventional or bioplastics,” says Martin Wagner, a biologist and professor in the Department of Biology at the Norwegian University of Science and Technology and an author on the 2020 study.
Wagner says the number of chemicals in regular and bioplastics can vary wildly, indicating that manufacturers could potentially engineer their products to be less toxic. “There must be some processes that work better than others,” he says. “I would love to see them [the companies] investing and designing safer and more sustainable materials. There’s a big potential for innovation. But they must acknowledge that they have a toxic problem in their bioplastics first.”
The European Bioplastics trade group has responded aggressively to research showing toxicity. It released a statement on the 2020 study led by Wagner saying, “bioplastics like all materials comply with the laws and regulations in force,” and that the study’s methods didn’t prove the toxicity of bioplastics. European Bioplastics also reached out to the University of Gothenburg, which then released a statement saying that Almroth’s 2023 study didn’t definitively attribute the toxic effects of PLA-lined paper to the PLA itself. European Bioplastics did not respond to Mongabay’s questions for this story.
In mid-March, a group of researchers in the European Union released a report sounding the alarm on plastic additives. They estimated that petroleum-based plastics contain 16,000 different chemicals, with 4,200 of them known to be highly hazardous and another 10,000 without sufficient hazard information.
Almroth says bio-based plastics show similar numbers, though researchers aren’t sure precisely how the additive mix differs between bio-based and petroleum-based plastics. They do know that there are a lot of chemical additives in bioplastics, and that bio-based plastics show signs of toxicity when tested in the lab.
The American Chemistry Council responded to the PlastChem report in a statement, saying the International Council of Chemical Associations supports efforts to bring transparency to plastic chemicals, and is developing an additives database and risk assessment framework.
But Almroth says, ‘There’s a massive lack of transparency and data reporting around these questions.” The researchers noted in their 2020 study that they repeatedly asked bioplastics suppliers for information about the kinds of materials used to make the products being tested, but didn’t get any definitive answers.
Almroth says she frequently experiences plastics industry stonewalling — a lack of transparency that hinders research and wastes taxpayer money by necessitating expensive chemical analyses. After the study on PLA-lined cups, “I had a lot of companies write to me, saying that they had this new nontoxic coating, but they wouldn’t tell me what it was,” she says.
International plastic treaty offers some hope
The Scientists’ Coalition for an Effective Plastics Treaty is calling for an independent expert body to develop safety criteria for all plastics, including the chemicals associated with bioplastics.
And the time to realize such sweeping global safeguards may be right now: The fourth session of negotiations to form a global plastics treaty is happening this week, running from April 23-29 in Ottawa, Canada. A majority of countries — particularly the 65-member nations of the High Ambition Coalition (HAC) — support a ban on what are called “chemicals of concern” in plastic, especially known carcinogens such as 4,4′-Oxydianiline, a substance used to create polymers. They are seeking to enshrine design criteria in the treaty for safer, more sustainable plastics.
But powerful nations, including the United States and China (both of which make vast sums of plastic and produce massive amounts of plastic waste), along with oil-producing nations such as Saudi Arabia and Russia, are not part of the High Ambition Coalition and have so far been resistant to tough binding treaty measures.
In the meantime, Almroth continues emphasizing that it’s not the type of plastic, but our throwaway culture, that is to blame for the environmental and public health menace that plastics have become. “You can’t always just work with replacing one thing with another thing. Sometimes we have to take away,” she says.
Wagner agrees, encouraging people to reduce their overall use of plastics wherever possible. “That is something that at least some of us can do. And then, of course, it’s asking for better regulation, asking for better policies, asking companies [to share information on] the chemicals that they sell to you in their plastic products.”
Almroth doesn’t think the plastics problem will be solved by encouraging altered consumer habits. “People have to be able to live their lives without getting sick and exposed to harmful or hazardous chemicals or products,” she says.
Banner image: Bioplastic samples being tested in a lab. Image by Jürgen Grünwald via Flickr (CC BY-NC-ND 2.0).
Citations:
Zimmermann, L., Dombrowski, A., Völker, C., & Wagner, M. (2020). Are bioplastics and plant-based materials safer than conventional plastics? In vitro toxicity and chemical composition. Environment International, 145, 106066. doi:10.1016/j.envint.2020.106066
Carney Almroth, B., Carle, A., Blanchard, M., Molinari, F., Bour, A. (2023). Single-use take-away cups of paper are as toxic to aquatic midge larvae as plastic cups. Environ Pollut. 1;330:121836. doi: 10.1016/j.envpol.2023.121836
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