Tourists from around the world will descend on Motor Speedway this Sunday (May 26) for the 108th running of the Indianapolis 500. Called “The Greatest Spectacle in Racing,” the Indy 500 is the preeminent event in all of American car racing, starring the sport’s creme de la creme.
The unsung heroes of the race are undoubtedly the pit crews, who in about 7 seconds can change four tires, gas up the 18.5 gallon tank, and make adjustments to the vehicle’s exterior for optimal performance. Burning through rubber like there’s no tomorrow, Firestone provides some 5,000 tires for the Indy 500, including the race plus the practice and qualifying rounds. But, while the smell of tire fumes hang over the Midwestern plain, another burning question is quietly stinking up the clean energy agenda: the massive pollution effects of EV tire emissions.
Rev Your Battery
A bombshell study gained attention earlier this year for its shocking findings on EV tire particulates. The research, authored by U.K. consulting firm Emission Analytics, found that EV brakes and tires released 1,850 times more particulate matter than tailpipes on conventional internal combustion engine (ICE) vehicles. The efficiency of ICE exhaust pipes has improved dramatically over the past few decades, to the point that most pollution produced by modern cars comes from tire wear. As EVs are about 30% heavier than conventional cars, they drive and brake with more force, leading to more frequent tire replacements. The EV battery is the main (and essential) component responsible for the extra weight. While an average EV battery weighs about 1,000 lbs, larger models such as the Tesla Model Y and the Ford F-150 Lightning can weigh closer to 2,000 lbs. The Emission Analytics study showed that adding 1,000 lbs to a mid-sized conventional sedan resulted in 20% additional tire wear and attendant particulate emissions. EVs also produce more torque than ICE cars due to their faster acceleration rates, exerting further stress on tires.
Tire particulates contain hundreds of pollutants. As Nick Molden, Emission Anlaytics’ President and CEO recently told the New York Post, “tires are made up of a lot of nasty chemicals.” Most concerning are the volatile organic compounds (VOCs) derived from petroleum-based synthetic rubber, such as benzene, toluene, and xylene. VOCs are responsible for ground-level smog that can cause and aggravate lung diseases such as asthma. These chemicals are also particularly dangerous when released in the form of ultrafine particles (measuring <23 nm) through tire exhaust, because they can enter human organs through the bloodstream. Benzene has notably been linked to certain forms of leukemia.
In addition to VOCs, tire pollution has also been implicated in the growing problem of microplastics in the oceans and in drinking water, occurring when tiny particles of synthetic rubber leak into watersheds. A 2017 study from the International Union for Conservation of Nature and Natural Resources estimated that tires contributed 28.3% of ocean microplastics, second only to the synthetic textiles industry (34.8%).
Moreover, tires contain heavy metals and chemical additives to improve tire performance and durability that can be lethal to wildlife. A chemical called 6PPD was found to be the culprit of a mass die-off of spawning coho salmon in the Pacific Northwest. When released into the air, 6PPD mixes with ozone to become 6PPD-quinone, which according to a 2020 paper, is acutely toxic to some fish species, such as coho salmon.
At the Starting Line
Emissions from tires during the course of their useful lifetimes is only one side of the story. The environmental impacts begin deep in the jungles of Southeast Asia, where the global demand for tires is leading to widespread deforestation, clearing biodiverse tropical rainforests for monoculture rubber tree plantations. An analysis by the Royal Botanic Garden published in 2023 used high resolution satellite imagery to determine that since the 1990s, between 10 and 15 million acres of forests in Southeast Asia had been bulldozed for rubber farms, an area about the size of Switzerland. Altogether, rubber plantations now occupy about 35 million acres across Thailand, Indonesia, Vietnam, and Cambodia, 70% of which supply the tire industry.
The global market for new tires is valued at $262 billion, with nearly 2.5 billion units sold worldwide in 2023. However, because EVs use 30% more tires over their lifetimes compared to conventional vehicles, the increasing demand for EVs is set to turbo-charge the world’s hunger for rubber. This will only accelerate rainforest decimation in regions identified as home to rare and endangered wildlife species.
Impacts on human health are also serious. A few months ago, a Lyft driver told me about his family in Thailand, who live near a recently built tire factory and have suffered a variety of respiratory illnesses as a result. He added that he believed the increased tire demand due to EVs was the main culprit in the surge of pollution-related diseases in his hometown. Indeed, Thailand is the world’s second largest producer of tires (behind China), supplying around 7% of global tire exports. The country’s market share in the tire industry is expected to deliver a compound annual growth rate (CAGR) of 5.2% through 2033.
While tire manufacturing remains a critical part of the Thai economy, representing nearly 20% of the country’s total export value, it comes at the cost of the environment and human health. According to the International Agency on Cancer Research, occupational exposure to rubber manufacturing processes, including tire curing, synthetic rubber production, and vulcanization, increases the risk of plant employees to leukemias, lymphomas and bladder cancer. Because limitations on fume emissions during manufacturing are not as strict in Southeast Asian countries as in Western countries, health impacts are more severe. Poor management of toxic effluents and poor ventilation systems in these factories likewise pass on these particulate emissions to the wider community, adversely affecting ecosystems and residential neighborhoods.
The Final Lap
There are a number of engineering and policy solutions currently in the pipeline to ameliorate excessive EV tire pollution. Bridgestone launched a new product line last year, the Turanza EV, designed specifically for the EV market. The Turanza is purported to provide superior durability and longevity over conventional passenger car tires. However, they are significantly more expensive, priced at $319 for 50K mile warranty, compared to the non-EV Turanza ($312 for 80K mile warranty).
Pilot programs for tire recycling are currently underway in some Southeast Asian countries. Rather than discarding tires in landfills or using the degraded rubber for other products, a circular economy turning old tires into new ones could help reduce waste streams.
Regulators in the U.S. and E.U. are also keen to implement new emissions standards for tires. The Euro 7 standard was passed by the European Parliament in 2023. In addition to new restrictions on tailpipe emissions for buses and trucks, Euro 7 , set to go into effect in 2025, will “limit particle emissions from tires and brakes and increase battery durability.”
In response to the coho salmon poisoning, the California Department of Toxic Substances Control (DTSC) recently passed a directive requiring manufacturers to find a safer alternative to 6PPD. Manufacturers are also required to notify DTSC regarding any products currently on the market containing 6PPD. The California Air Resources Board (CARB) is also urging manufacturers to research the reduction of weight in non-battery EV components to lighten the load.
These remedies may be a step in the right direction. But the immovable object of lawmakers’ mandates for EVs inevitably meets the unstoppable force of humanity’s need for speed. Oh, how I love the smell of VOCs in the morning.
Electrically yours,
K.T.
Thank you K.T. for getting around to the topic of tire-related pollution - and how EVs exacerbate the air and water pollution problems.
Good One KT!
The polymer chemistry of tires and additives is fascinating and big business. Balancing traction and wear is a lab art.
The sticky performance tires are not a big issue particulate wise, it's the high mileage compounds and EVs that throw off the fines.
As an industrial chemist I was exposed to a lot of methyl ethyl bad shit. But particulates are the worst as they can lodge in lung tissue and stay there doing bad deeds.