In a laboratory study, researchers in Vienna discovered toxic additives from the wear of car tires in lettuce. The tire particles end up in the fields via wind, sewage sludge and wastewater, where the pollutants and sometimes highly toxic chemicals they contain can end up in the vegetables.
Car tires are an important source of microplastics. The magnitude of tire particulate emissions is still poorly quantified, according to the scientists led by environmental geoscientist Thilo Hofmann of the Center for Microbiology and Environmental Systems Science at the University of Vienna in their work, which was published in the journal “Environmental Science & Technologies”. Each year, about one kilogram of tire particles per inhabitant is blown into the environment by the wind and washed into rivers and sewers by rain. For example, the tire particles can end up on agricultural land. This also happens with sewage sludge, which is used as fertilizer in agriculture.
The particles contain additives that provide certain driving characteristics or durability in car tires. As Hofmann’s team has shown in previous studies, the microplastics usually release potentially harmful chemicals into the top layers of the soil.
chemicals added
In their current study, the scientists conducted several experiments to investigate whether edible plants absorb the pollutants. To do this, they added five chemicals to the nutrient solutions of lettuce plants in the lab, which are used in tire manufacturing or formed as a conversion product when the tires are used. Not all of these chemicals have yet been classified as harmful, but the metabolite “6PPD-quinone” has been found to be toxic and has been linked to the mass extinction of salmon in the US, for example.
“Our measurements showed that the lettuce plants took up all the compounds we examined through the roots, transferred them to the lettuce leaves and accumulated there,” says Anya Sherman of Hofmann’s team. This uptake also occurred when the lettuce plants were not exposed to the chemicals directly, but indirectly via tire granules in the root area.
The researchers also identified those substances formed from the chemicals absorbed during the plant’s metabolism. These metabolites are compounds that have not yet been described, the toxicity of which is unknown and therefore “present an unpredictable health risk”, emphasizes Thorsten Hüffer of Hofmann’s team.
In a next step, the scientists want to investigate how the processes observed in the laboratory take place in natural soils. The range of additives is also being expanded.
Microplastics harmful in the long term
How microplastics can pollute the environment in the long term, Hofmann’s research group recently showed in another study, also published in the journal “Environmental Science & Technology”: The scientists focused on additives mainly used in the production of PVC – the so-called “phthalates”. ”. Their analyzes have shown that the PVC microplastics studied can release these plasticizers into aquatic systems such as rivers, lakes or groundwater for more than 500 years. The extent to which this happens always depends on the environmental conditions.
Source: Krone
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