A report from the Pew Charitable Trust found that 78 percent of ocean microplastics are from synthetic tire rubber. These toxic particles often end up ingested by marine animals, where they can cause neurological effects, behavioral changes, and abnormal growth. 

Meanwhile, British firm Emissions Analytics spent three years studying tires. The group found that a single car’s four tires collectively release 1 trillion “ultrafine” particles for every single kilometer (0.6 miles) driven. These particles, under 100 nanometers in size, are so tiny that they can pass directly through the lungs and into the blood. They can even cross the body’s blood-brain barrier. The Imperial College London has also studied the issue, noting that “There is emerging evidence that tire wear particles and other particulate matter may contribute to a range of negative health impacts including heart, lung, developmental, reproductive, and cancer outcomes.”

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