Polymers—very large molecules—are thought to be too big and inert to migrate out of products or into people and therefore pose no health risks. As a result, polymers are used in a variety of everyday products from clothing to cosmetics and have largely avoided regulation worldwide. For example, Canada just initiated a process to regulate the entire class of per- and polyfluoroalkyl substances (PFAS) in products—except for PFAS polymers. Similarly, polymers are exempt from the Toxic Substances Control Act (TSCA) in the U.S. and REACH in the E.U.
That’s why as more harmful small chemicals are banned or phased out, the chemical industry is moving to using large molecule polymers which get a free pass from the testing and regulation that are required for other chemicals.
However a breakthrough peer-reviewed study published this month in Nature Sustainability questions the long-held belief that polymers are harmless, finding that they can break down into smaller more harmful chemicals. This study provides important new evidence that polymers need to be tested and regulated before they can be used in products.
The Trojan Horse Effect
“Our study suggests polymers can act as a Trojan horse for toxic chemicals,” explains Da Chen, senior author and scientist at Jinan University in China. Polymers, often marketed as “non-toxic” alternatives, are added to products as stable, large molecules. However, over time, they can break down, releasing harmful byproducts into the environment and potentially into our bodies.
The research focused on two polymeric brominated flame retardants (polyBFRs), widely used in electronics as substitutes for banned flame retardants. Alarmingly, both polyBFRs were found to degrade into dozens of smaller molecules. Toxicity tests on zebrafish exposed to these breakdown products found abnormalities in the brain, heartbeat and locomotor activity, as well as a curved spine and decreased body length. Such effects have previously been linked to effects from exposure to TBBPA monomers—the smaller molecules that make up the polyBRs.
The study didn’t stop with lab tests. Researchers also searched for these polymer breakdown products near electronic waste recycling facilities and found them in soil, air, and dust. The highest concentrations were detected closest to the facilities, with the levels decreasing further away from these sites. This discovery highlights how the widespread use of polyBFRs in electronics can contribute to environmental pollution and increased exposure and potential for health harm to humans and wildlife.
These chemicals appear to be used at high volumes, making the potential scope for harm considerable. The chemical producers and their trade groups have promoted polyBFRs as environmentally friendly and non-hazardous substitutes for banned monomeric flame retardants (e.g., hexabromocyclododecane and decabromodiphenyl ether) to meet flammability standards for electronics, building materials, vehicles, and more. Also noteworthy is that the real-world fire-safety benefits for many of these standards have not been demonstrated.
Beyond Flame Retardants: Implications For Other Polymers Like PFAS
The findings also have broader implications for other polymers used in consumer goods, such as PFAS polymers. Fluorinated polymers are found in everything from children’s uniforms to food packaging to cosmetics. Other studies have shown that PFAS polymers release smaller more toxic PFAS molecules over time. Despite industry claims that fluorinated polymers should be exempt from regulation, scientists maintain that they belong to the same hazardous class as other PFAS chemicals.
Moreover, many types of polymers are formulated with additives like plasticizers and stabilizers to enhance their performance. These additives can leach out of products during use or disposal, exposing humans and the environment to chemicals with known toxic effects.
Closing The Loophole
Polymers are being added to products we touch, wear, sit on, or eat from with little oversight. For example, under TSCA in the U.S., manufacturers can self-certify that their polymers meet certain criteria—such as high molecular weight or low solubility—that supposedly render them harmless. This allows them to forgo comprehensive toxicity testing or lifecycle assessments.
As a result, polymers and their harmful breakdown products are used in electronics, textiles, food packaging, plastics, and more. This widespread application increases the likelihood of environmental contamination and human exposure. Children are particularly vulnerable due to their developing body systems and higher exposure rates relative to body weight.
Exempting polymers from toxics regulations is a policy rooted in outdated science. While the intent was to streamline oversight for low-risk substances, new evidence underscores the need for comprehensive evaluation of polymers throughout their lifecycle. It’s time for policymakers to act decisively by closing these regulatory loopholes. The stakes are too high to continue treating polymers as inherently safe when so much evidence suggests to the contrary.