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Tiny particles of rubber cast off by car tires, which have long been known to harm wildlife, may also pose a risk to humans, according to a new study.
The chemical 6PPD, which is added to tires to prevent cracking, transforms when exposed to ozone pollution, which arises from car exhaust. One compound formed from this process, 6PPD-quinone, has been implicated in the deaths of spawning coho salmon in the Pacific Northwest. For decades, heavy rains have led to surges in salmon deaths as polluted stormwater washed into urban waterways.
The new study finds that many of the other chemicals derived from tire wear may pose a threat to humans when inhaled. “When you oxidize one chemical from a tire, it probably makes hundreds of chemicals in the mixture,” said coauthor John Liggio of Environment and Climate Change Canada.
To understand the potential health risks from tire pollution, researchers exposed human immune cells to a mixture of tire-derived pollutants as well as 6PPD-quinone on its own. The mixture caused rapid cell death, among other harms, according to the research, published in the journal Environment International. The findings, though far from conclusive, indicate that the risks from airborne tire pollution may be greater than realized.
Notably, 6PPD-quinone was not found to be particularly harmful to human cells on its own, said lead author Ali Abdul-Sater, of York University in Toronto. “This suggests,” he said, ”that focusing on a single compound may substantially underestimate the real health risks associated with tire-derived air pollution.”
