Toxic chemicals from tires could be filling your dinner plate through soil contamination

VIENNA, Austria — Toxic chemicals from car tires could end up on our dinner plates as more and more vegetables "ingest" pollutants, a new study warns. Researchers in Austria discovered that when particles from car tires break off, they leave a trail of potentially dangerous substances. These particles then travel with the wind and rain, ultimately ending up in rivers and sewage systems.

Wastewater and sewage sludge are often used as fertilizers in agriculture, which means tire particles can contaminate agricultural soils, affect growing plants, and potentially render them unsafe to eat. On average, the team from the University of Vienna says a person unknowingly leaves behind around one kilogram (2.2 pounds) of potentially toxic particles each year.

"Tire wear particles contain a number of organic chemicals, some of which are highly toxic," says Anya Sherman, a PhD student at the Centre for Microbiology and Environmental Systems Science (CMESS) and co-first author of the study.

"If these chemicals are released in the root zone of edible plants, they can pose a health concern for consumers – provided the chemicals are taken up by the plants," adds Thilo Hofmann, head of the research group, in a university release.

To reach their results, scientists added five chemicals to a lettuce plant. Four of these chemicals are ingredients in tire production, but not all of them have a proven history of being harmful. However, scientists have confirmed that the fifth chemical, called 6PPD-quinone, toxic. While it isn't a part of the tire production process, it is byproduct once people start using their new tires. Researchers have linked this particular chemical to mass deaths of salmon in the United States.

"Our measurements showed that the lettuce plants took up all the compounds we investigated through their roots, translocated them into the lettuce leaves, and accumulated them there," reports Sherman.

This also occurred when the lettuce plants were not directly exposed to the chemicals, but rather indirectly via the tire residue left behind.

"The lettuce plants continuously take up the potentially harmful chemicals that are released from the tire abrasion particles over the long term," reports Hofmann.

The substances from tires also interacted with the lettuce plants and produced new compounds. These compounds are unknown to scientists, meaning they cannot determine if they are toxic or not.

"The plants processed the substances and, in doing so, produced compounds that have not been described before. Since we don't know the toxicity of these metabolites, they pose a health risk that cannot be assessed so far," emphasizes Thorsten Hüffer, senior scientist at CMESS.

The team plans to trace the possible path of tire-wear pollutants from the road to the plate.

"The processes we have investigated probably take place differently in soil systems. In a next step, we are therefore looking at the possible uptake of tire additives by plant roots in natural soils," reports co-author Ruoting Peng, who, in her dissertation project, traces the presence of an even wider range of additives in the environment, focusing on the pollution of water bodies.

Pollutants from man-made objects are scattered all over the planet, with oceans, rivers, and lakes suffering greatly from their contamination. The researchers have previously investigated how long microplastics can continue releasing pollutants into water. They found that some can continue releasing harmful substances for over 500 years. This previous research focused on phthalates, additives that are used mainly in the production of PVC to provide flexibility and stability. PVC is one of the most commonly used plastics.

"These plasticizers have already been detected everywhere in the environment. Yet, little is known about their release process from the microplastics and how environmental conditions can influence the release," explains the first author of this study, Charlotte Henkel. "Our analyses have shown that the PVC microplastics studied can release phthalates into aquatic systems – for example, rivers, lakes, or groundwater – over more than 500 years."

"Once microplastics have reached the aquatic environment, they remain a source of potentially polluting substances, and in the case of phthalates, for a very long time," notes Hofmann.

This research highlights the potential dangers associated with tire-wear particles and other pollutants from man-made objects. As these substances find their way into our environment, they pose significant risks to the health of ecosystems, wildlife, and humans.

Understanding the full extent of these risks and the processes through which pollutants are released and absorbed by plants and other organisms is critical to developing effective strategies for mitigating their impact. Further research is necessary to explore the release of toxic substances from microplastics, tire particles, and other sources, as well as their long-term effects on ecosystems and human health.

In the meantime, the team says it is essential for governments, industries, and individuals to take action to reduce pollution, minimize the use of harmful chemicals, and promote sustainable practices to protect our environment and ensure the safety of our food supply.

This study is published in the journal Environmental Science & Technology.

Just like rubber particles coming off of tires, plastic pollution has a long history of contaminating the food we eat. Recently, scientists revealed that a new disease is killing seabirds and may be spreading to other species as well.

Unlike other viruses that sweep through nature, this one is result of plastic pollution. The international team is calling this new disease plasticosis, a condition with a direct link to the consumption of plastic particles in the environment.

This new report looked at the specific issues which are now plaguing birds like the Flesh-footed Shearwater of Australia. The study found that ingesting plastic directly affects the proventriculus organ – the first part of a bird's stomach.

Although the new study focused on one species in Australia, researchers warn that plasticosis is likely affecting other species around the world, based on the scale of plastic pollution globally.

"Our research team has previously looked at how microplastics affect tissues," says Dr. Alex Bond, Curator in Charge of Birds at the Natural History Museum. "We found these particles in organs such as the spleen and kidney, where they were associated with inflammation, fibrosis and a complete loss of structure."

South West News Service writer Alice Clifford contributed to this report.

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Study Finds sets out to find new research that speaks to mass audiences — without all the scientific jargon. Study Finds has been writing and publishing articles since 2016.

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