Chemicals from car tires are in leafy greens: study

This study might make you want to push the brakes on filling your plate with heaps of certain veggies.

Chemical additives from car tires have ended up in leafy greens, according to a new study. 

Researchers at the Centre for Microbiology and Environmental Systems Science at the University of Vienna and the Hebrew University of Jerusalem published their findings in the journal Frontiers in Environmental Science last month. 

They said that the chemical additives in car tires end up in agriculture through atmospheric deposition, meaning the chemicals travel to plants via precipitation in the atmosphere.  

Leafy greens absorb them through irrigation with treated wastewater and the use of sewage sludge as fertilizer.

“There they can be taken up by plants and thus also reach humans,” Thilo Hofmann, head of the research group, said in a press release. 

Car tires include a mixture of substances to make them more durable and improve their performance. Around 5% to 15% of these substances are chemical additives, which find their way into our food. 

“The toxicity of tire and road wear particles is related to their organic additives and associated transformation products,” Anya Sherman, Ph.D. student at the Centre for Microbiology and Environmental Systems Science and first author of the recently published study, explained.

The researchers analyzed vegetables from both Switzerland and Israel and calculated people’s daily intake to determine how many chemicals they were consuming. 

“We examined real samples from supermarkets in Switzerland and field vegetables from Israel,” Hofmann explained. 

The vegetables in Switzerland came from Italy, Spain and Switzerland, and the Israeli vegetables were field vegetables studied after harvest. 

Luckily, the concentration of tire additives was low. 

Depending on a person’s diet, their daily intake may be 12 to 1,296 nanograms of an additive called benzothiazole and 0.06 to 2.6 nanograms of 6PPD, which is toxic to certain fish, like coho salmon. 

The researchers said the concentrations of tire additives in vegetables are similar to the amounts of drug residue found, which, previous studies reported, also make their way into leafy greens. 

“While the concentrations and daily intake are fortunately relatively low, additives from car tires are still found in food. That’s not where they belong,” Hofmann said. 

Hofmann said more research is needed to determine the impact these food additives have on human health and the environment. 

Scientists first discovered that car additives could be absorbed by plants in 2023. 

“However, the question was whether this only happens in our mechanistic laboratory study or also in the field,” Sherman said.