You probably haven’t given a lot of thought to the damaging effects of tire wear, at least when it comes to our food supply. But a study out of the University of Vienna (UV) will likely change your perspective on that. 

With concern for at least five known toxins in tire wear products (TWPs), researchers grew lettuce in a hydroponic system, adding TWPs to the water to measure the effect. They found the chemicals traveled up to the edible leaves of the plants. Although the toxicity of some of the pollutants tested are unknown, there’s strong evidence measuring the link between a compound known as 6PPD-quinone and mass salmon deaths. As evidenced in a study reported in Science, even a small exposure to 6PPD-quinone killed Coho salmon in the lab environment. Based on that information, the study at UV explored how TWPs in streams and other water sources could impact the safety of agricultural products. 

Related: Researchers develop new stronger concrete from scrap tires

“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,” said Anya Sherman, PhD student at the Centre for Microbiology and Environmental Systems Science (CMESS) and co-first author of the study.

Taking it a step further, the team added whole tire pieces to the water to measure the absorbance. They discovered the lettuce still metabolized the chemicals. The research is young, but the conclusions of the study lead to more questions. 

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

This specific study measured absorption via hydroponics and with the concerns produced from the results, the team will move on to evaluate the effects of adding TWPs to a soil-based growing environment instead. 

Throughout the experiment, the lettuce plants were exposed to diphenylguanidine (DPG), hexamethoxymethylmelamine (HMMM), benzothiazole (BTZ), N-phenyl-N′-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) and its quinone transformation product (6PPD-q). The study found lettuce readily absorbed TWP-derived compounds, with maximum concentrations ranging from approximately 0.75 μg g–1 for 6PPD to 20 μg g–1 for HMMM. Although the plants metabolized these compounds, several transformation products were identified, many of which proved to be more stable in lettuce leaves than the parent compounds.

The environmental impact TWP

What’s bad for the body is likely also bad for the environment and vice versa. While this specific study resulted in more questions than answers, the data is compelling enough to spark valid concerns for both humans and nature. 

According to the study, TWP emissions into the environment are estimated to be around 5.9 million tons per year worldwide. These particles can reach farmland soils through air, road runoff and the application of biosolids from wastewater treatment plants (WWTP). In Germany alone, it is estimated that between 1400 and 2800 tons of TWP are deposited on agricultural land annually through biosolid application. 

TWP introduce a wide range of organic compounds to farmland soils, and their effects on biota remain largely unknown. However, this isn’t the first study to identify environmental issues linked to tires. In fact, there are several conclusions scientists have previously established. 


As tires wear down over time, they release small particles known as microplastics into the environment. These microplastics are a significant contributor to plastic pollution in our ecosystems. They can contaminate soil, water bodies and even the air we breathe.

Water contamination

Tires contribute to water pollution in various ways. When it rains, water washes away tire particles from roads and deposits them into streams, rivers and other bodies of water. The chemicals and heavy metals present in tires can leach into the water, posing risks to aquatic life and potentially entering our drinking water sources.

Tire fires

Tire fires are a significant concern due to the environmental damage they cause. When tires catch fire, they release toxic smoke and pollutants into the air. These emissions contain harmful chemicals and pollutants, including dioxins, heavy metals and polycyclic aromatic hydrocarbons (PAHs), which can have detrimental effects on air quality and human health.

Habitat destruction

Improperly disposed of tires often end up in landfills or abandoned sites, leading to habitat destruction and a challenge for animals. Accumulated tires create breeding grounds for pests and disease-carrying insects, disrupting the natural balance of ecosystems. Furthermore, tire piles can serve as fire hazards and are challenging to manage and clean up.

Soil contamination

Tires contain a variety of chemicals and heavy metals, such as zinc, lead and cadmium. When tires degrade or are improperly disposed of, these substances can leach into the soil, posing risks to plant life and potentially entering the food chain. Contaminated soil may require extensive remediation efforts to restore its health and fertility.

Carbon footprint

The tire manufacturing process and the energy required for their production contribute to greenhouse gas emissions. Additionally, the disposal of tires through incineration or landfilling releases carbon dioxide and other pollutants into the atmosphere. This contributes to climate change and further environmental degradation.

These definitive research conclusions amplify the importance of implementing proper tire management practices, such as recycling, finding alternative uses for waste tires and raising awareness about the environmental impact of tire disposal. 

Building on that knowledge, the UV lettuce study accentuates the need for a better understanding of the impact our daily commute has on the food we eat. 

Via New Atlas 

Images via Pexels