Chemical substances released by car tyres can be found in leafy vegetables eaten by humans, according to new research shedding light an environmental impact of both electric and combustion-engined vehicles.
Car tyres consist of a complex mixture of materials to improve their performance and durability. This also includes chemical additives, which comprise hundreds of substances.
Once released from the tyres, these particles are being washed into sewage treatment plants when it rains, say environmental scientists at the University of Vienna, and the sewage that accumulates there is often spread on fields as fertiliser.
"There they can be absorbed by plants and thus also reach humans," said Hofmann, head of the research group. The samples were analysed for a total of 16 chemical compounds that are associated with tyres.
The study, which analysed vegetables grown in Switzerland, Italy, Spain and Israel, was published in the scientific journal Frontiers in Environmental Science and confirms the results of an earlier laboratory study.
This finding also reflects other research that has found residues from medicines in plant foods.
Although the concentration of the substances was low, the evidence was nevertheless clear, and the results are transferable to other countries, said Thilo Hofmann from the Centre for Microbiology and Environmental Systems Science at the University of Vienna (CeMESS).
"While the concentrations and daily intake are fortunately relatively low, substances from car tyres are still found in food. That's not where they belong," said Hofmann.
The next steps should now be to investigate the health aspects. The study is a collaboration between CeMESS and the Hebrew University of Jerusalem.
According to previous research, around 500,000 tons of tyre abrasion are produced in the EU every year. In Germany, synthetic rubber, which is one of the plastics, accounts for around one third of all micro-plastic emissions as abrasion from car tyres.
The majority of tyre and road wear remains on the roadway or close to the carriageway. Most of it is collected and discharged by road surface water when it rains. It then seeps into the soil, causing pollution, or drains into sewers and makes its way into rivers and oceans.
While the impact on the environment is massive, tyre-wear particles are not known to be as harmful to humans as particulate matter from other sources such as brakes and road surfaces, which has been linked to millions of annual premature deaths, mostly in city dwellers.
Only a very small fraction of the tyre particles remains in the atmosphere over a longer period of time and affects humans via the air they breathe. Compared to smaller particulate matter, the tyre particles are very coarse and do not penetrate deeply into the human respiratory tract.
