Tires are unfortunately anything but benign

At the onset of winter many of us go through the seasonal ritual of changing tires. Thetford residents often go to the garage in East Thetford run by Mike Watson for this service. And as far as driving safety is concerned, that’s a good thing. In colder weather, below 45 degrees F according to tire manufacturers,  all-season tires become stiff and lose traction.  Snow tires are made of a type of tire compound that remains supple and compliant at temperatures below freezing. It’s this ability to hug the road surface in the cold that gives winter tires their grip.

But no matter what tires we use, they all wear out eventually. In the U.S., the average car sheds about 5 pounds of tire material a year in the form of particles and fine dust. In Europe where driving distances are shorter, 2.5 pounds of tire material is shed per car per year. Interestingly, electric cars shed 20% more tire material than gasoline-powered cars because they are heavier and have greater torque, thus wearing out tires faster.

Tires are usually viewed as benign; indeed 2 billion – enough to reach the moon if stacked – are sold every year. Recycled tire material makes its way into many products, such as rubber floors, playground structures, mats, and running tracks, as well as rubberized asphalt and rubber-wrapped railroad ties. Old tires are also used, as is, for erosion control.

The fact that toxins are released from tires came to light as a result of 20 years of research into the cause of huge die-offs of spawning coho salmon in western streams following rainfalls. The researchers found that salmon were quickly poisoned by water containing particles from tires. Out of the hundreds of chemicals in this water, they traced the cause of mortality to a chemical known as 6-PPD, an anti-oxidant that is incorporated into tires to protect them from cracking and degradation. In the environment, 6-PPD from tire dust is converted to many other chemicals, including 6-PPD-quinone, which is lethal to several fish species, including coho salmon.  It is now recognized as one of the most harmful chemicals known and probably the most ubiquitous. 

This is just the tip of the iceberg in terms of toxins released by tire wear. Tire rubber compound contains more than 400 chemicals, including heavy metals, and many of them are carcinogenic. According to one expert, tires that are just sitting there release 100 times more volatile organic compounds than come from the tailpipe of a modern car. “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, the 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.”

One group of compounds that are known to pose a threat to workers who handle tires are polycyclic aromatic hydrocarbons (PAHs) that come from the use of high-aromatic oils in tire production. They are linked to off-gassing of carcinogenic benzene, naphthalene, and other compounds that are toxic to people in very low amounts. In addition, sunlight acts on them to make ozone or ground-level smog that contributes to respiratory illness.

The amount of particles produced by tire wear is also a huge concern. The four tires of a car release 1 trillion ultra fine particles for each kilometer driven, as well as larger particles. Ultra fine particles are so tiny they are able to pass through lung tissue into the bloodstream and then cross the blood-brain barrier. They remain suspended in the air and in road runoff that carries them into streams and rivers. A report from London University cited data that, globally, tires produce 6 million tons of particles a year, and 200,000 tons of them wind up in oceans.  The Pew Charitable Trust reported that 78 percent of ocean microplastics are synthetic rubber from tires, which breaks down far more slowly than natural rubber. Microplastics are ingested by marine life forms and can produce side effects which include neurotoxicity, stunted growth, and abnormal behavior. It is not surprising that plastic particles have been found in the gills and stomachs of seafood en route to being consumed by people.

Tire manufacturers have responded by forming the Tire Industry Project to investigate ways to reduce emissions from tires. Unfortunately there is no substitute for 6-PPD on the horizon, and old tires are recycled to become a constituent of new tires. However one company, Nokian, has already phased out the use of high-aromatic oils in their tire production and is incorporating more non-fossil, renewable oils like canola and “tallol,” a by-product of the kraft process of manufacturing wood pulp from coniferous trees. 

As an auto mechanic who is exposed to tire out-gassing and dust all the time, Mike Watson is enthusiastic about these developments and happy to supply this brand of tires to all who inquire.

Photo credit Li Shen