For decades, concerns about automobile pollution have focused on what comes out of the tailpipe. Now, researchers and regulators say, we need to pay more attention to toxic emissions from tires as vehicles roll down the road.

“You’ve got a chemical cocktail in these tires that no one really understands and is kept highly confidential by the tire manufacturers,” said Nick Molden, CEO of Emissions Analytics. “We struggle to think of another consumer product that is so prevalent in the world and used by virtually everyone, where there is so little known of what is in them.”