The short answer is that if you note a scent, some of the chemicals responsible for the aroma are finding their way into your body. Whether or not these are harmful depends on which specific compounds are absorbed, and to what extent. As always, toxicity is a question of dose. There is no doubt, however, that tires do contain some potentially nasty compounds.
Rubber tires are a technological marvel, one without which our most popular modes of transportation, namely automobiles, buses and planes, would grind to a halt. And it takes a host of chemicals to keep those tires rolling along. Dozens and dozens of chemicals. There are sulphur-based “vulcanization” agents that link rubber molecules together to keep tires from becoming too stiff when temperatures drop or too soft when they rise. “Accelerators” help speed up the vulcanization, antioxidants and antiozonants prevent the degradation of rubber on exposure to oxygen or ozone. Fillers like carbon black and silica confer elasticity, toughness and resistance to abrasion. Hydrocarbon oils are used to control viscosity, disperse the various processing chemicals and to “extend” the amount of rubber, basically making less rubber go further. Carbon disulphide is a solvent used to dissolve the rubber as it is being processed. The exact chemicals used in tire manufacture are proprietary and tire formulas are closely guarded trade secrets.
Analysis of the vapours that are released from tires reveals the presence of numerous compounds that constitute the “tire smell.” Some of these, mostly those emanating from the hydrocarbon oils, are potentially toxic. Some, like benzopyrene, are carcinogenic. Occupational exposure can often offer a glimpse into toxic effects of chemicals, but in the case of the tire industry, there are no significant studies, although one small study did suggest an increased risk of heart disease among workers who process tire chemicals.
An educated guess would be that long term exposure to tire smell should be avoided, particularly by people with respiratory problems. Curiously, there are people who love the scent of new tires, some even describing an addiction to the fragrance. Amazingly, there is even a woman who just loves to chew on tire shavings! Since her addiction began, she has consumed about fifty tires and seems not the worse for wear except for the occasional upset stomach. She claims she is not worried about the chemicals in the tires but does take the precaution of washing the rubber before giving her jaws a workout. I, on the other hand, would have some concern about treating my body to a snack featuring the likes of phenantrene, chrysene, benzylbutyl phthalate and benzothiazole. I would suggest chewing gum instead. Or better yet, an apple.
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