Researchers have detected toxic additives from the abrasion of car tires in lettuce in a study. The tire particles enter the fields through wind, sewage sludge and wastewater, where the pollutants they contain can enter the vegetables.
As the scientists showed in experiments, lettuce plants absorbed all five chemicals studied, some of which were highly toxic. Their study appeared in the journal Environmental Science & Technology.
Car tires are a significant source of microplastics that pollute the environment. The extent of tire particle emissions remains poorly quantified, scientists led by environmental scientist Thilo Hofmann of the Center for Microbiology and Environmental Systems Science at the University of Vienna write in their paper. As they write in a news release, about one kilogram of tire particles per inhabitant per year is blown into the environment by wind and washed by rain into rivers and wastewater.
In their study, the scientists conducted several experiments to determine whether edible plants absorb the pollutants. To do so, they added five chemicals used in tire manufacturing to the laboratory’s nutrient solutions for lettuce plants.
“Our measurements showed that the lettuce plants took up all the compounds we studied through the roots, translocated them into the lettuce leaves and accumulated them there,” said Anya Sherman of Hofmann’s team. This uptake occurred even when the lettuce plants were not exposed to the chemicals directly but indirectly via a hoop granule in the root region.
The researchers also identified substances formed during the plant’s metabolism from the ingested chemicals. These metabolites are undescribed compounds whose toxicity is unknown and, therefore, “pose a health hazard that cannot be assessed,” emphasized Thorsten Hüffer from Hofmann’s team.
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