IF INNER FITNESS | Special Chapter - The Tire Vanished.

Our IF Inner Fitness journey continues with a special added chapter. This chapter and all chapters are copyrighted, 1999 - 2025.

The Tire Vanished.

Examining Tire-Derived Toxins as Environmental Contributors to Disease.
A possible overlooked link to autism, developmental disorders and other serious health issues.

I had NO intention of writing this article. Infact, I was writing a completely different article about the difference between regular automotive tires and EV tires. As I read, ideas began to take shape. My last article was about the many possible causes and links to autism, ADHD, allergies and other serious diseases. As I read about tires I began to “connect some dots”. It’s the oddest thing. Everyone thinks about emissions. That’s easy. Perhaps because we can see it and it’s all the media talks about every day, but what about tires? I mean, we replace them all the time. Where do they go? It’s something we never really think about.

Let’s start with some interesting data. Every vehicle on the road sheds microscopic rubber particles (micro plastics). Globally, this produces more than 6 million tons of tire particles annually, with over 200,000 tons reaching the world’s oceans. While much attention has focused on “microplastics” as a broad environmental concern, this article examines the toxic chemical micro-plastics that tire particles carry into our bodies.

Unlike generic microplastics, tire wear particles contain a distinct and dangerous mix of neurotoxic heavy metals; including lead, cadmium, copper, zinc, and manganese, as well as a chemical additive called 6PPD (a chemical used in tires to prevent them from cracking and deteriorating due to ozone and oxygen exposure). When this chemical comes into contact with ozone in the air, it transforms into another compound called 6PPD-quinone, (6PPD-q) which is extremely toxic.

Introduction

Tire wear particles (TWPs) represent an emerging but under recognized environmental and public health concern. While attention has historically focused on auto emissions as the dominant form of vehicular pollution, advances in combustion efficiency and the rise of electric vehicles (EVs) have shifted the pollutant focus towards non-exhaust sources. Among these, TWPs are increasingly understood to be one of the largest contributors of micro and nano-particulate matter in urban air, aquatic systems, and soils. Yet, despite their ubiquity, they remain largely unregulated, and their biological impacts insufficiently characterized.

Unlike exhaust emissions, which have been extensively studied and legislated, TWPs are generated through mechanical abrasion of tires against road surfaces. Each tire contains a complex mixture of synthetic rubbers, plasticizers, metals, and chemical additives designed to enhance performance and durability. As tires degrade, friction and heat pull or lift microscopic fragments of these materials into the environment. These particles range from micrometers down to the nanoscale, with smaller fractions capable of atmospheric suspension, long range transport, and of course human exposure.

Recent findings have demonstrated that TWPs may contribute as much as 1,000 times more particulate pollution than exhaust emissions in newer vehicles. With EVs being heavier on average due to battery weight, this imbalance is projected to increase further, creating yet another EV paradox in which vehicles designed to reduce emissions may inadvertently amplify non-exhaust toxicity.

Composition of Tire Wear Particles

The material composition of TWPs is highly diverse in content, reflecting the proprietary formulations of tire manufacturers. A single tire can contain over 400 individual chemical constituents. Major components include styrene-butadiene rubber (SBR), butadiene rubber (BR), and natural rubber, each modified with plasticizers, stabilizers, vulcanization accelerators, and antioxidants. These serve critical functional roles but become potential toxicants once liberated and degraded in the environment.

Among the most concerning compounds identified are 6PPD-quinone (6PPD-q), a transformation product of the antioxidant 6PPD. Initially intended to prevent tire cracking from ozone exposure, 6PPD converts into 6PPD-q upon contact with ozone, forming one of the most toxic and persistent chemical derivatives currently detected in road runoff. 6PPD-q has been implicated in acute mortality events among coho salmon and demonstrates potent cytotoxic and neuroactive properties in mammalian models.

Additional ingredients of concern include zinc oxide, used as a vulcanization catalyst; polycyclic aromatic hydrocarbons (PAHs); benzothiazoles; phthalates; bisphenols; and various heavy metals, and this is important (e.g., lead, cadmium, and nickel) and 6PPD-q. Many of these compounds are recognized endocrine disruptors, carcinogens, or neurotoxins. Once released, TWPs undergo environmental weathering, further transforming into smaller, more bioavailable derivatives capable of leaching into air, water, and food chains.

Exposure Pathways.

Tire wear particles enter the environment through multiple, interconnected pathways. In the atmosphere, fine particulate fractions remain suspended and are inhaled directly. Larger particles deposit onto roadways and are transported via stormwater runoff into soil and aquatic ecosystems, where they settle in sediments or are ingested by aquatic organisms. Leaching from landfills and road dust resuspension also serve as secondary release routes.

Inhalation represents the most direct route of human exposure, particularly for ultrafine particles capable of translocating across the alveolar epithelium into systemic circulation. Once in the bloodstream, these particles can cross the blood-brain barrier, accumulate in neural tissue, and interact with neuroimmune signaling pathways. Dermal and oral exposures occur through contact with contaminated soil, dust, or food sources, especially in children, who exhibit greater hand-to-mouth behaviors and heightened vulnerability to environmental toxicants.

Emerging research suggests that TWPs can persist in indoor environments as well. Particles carried indoors on footwear or clothing may accumulate in household dust, extending exposure beyond outdoor air quality concerns (makes you think twice about running or exercising in a city or along a busy highway).

Health Implications: Neurodevelopmental and Systemic Effects.

The toxicological impacts of TWPs are multifaceted, reflecting both their chemical composition and nanoscale behavior. Unlike traditional particulates, which primarily exert oxidative or inflammatory stress through bulk deposition, the molecular constituents of TWPs may act through endocrine, mitochondrial, and neurochemical mechanisms.

Neurotoxicity and developmental outcomes: Laboratory and epidemiological studies have linked exposure to tire-derived compounds such as benzothiazoles, PAHs, and 6PPD-q to neurodevelopmental disruption, behavioral alterations, and impaired synaptic function. Experimental data demonstrate dopaminergic and serotonergic dysregulation following exposure to TWP contaminates, paralleling neurochemical profiles observed in conditions such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). These findings suggest that TWPs may represent a previously under appreciated environmental contributor to the rising prevalence of neurodevelopmental disorders.

Endocrine and reproductive disruption.

Tire additives including phthalates and bisphenols mimic or interfere with hormone signaling pathways, affecting reproductive development and metabolic regulation. Chronic exposure has been associated with reduced sperm quality, altered sex hormone ratios, and thyroid dysfunction.

Cardiopulmonary and inflammatory effects.

Inhaled TWPs induce oxidative stress and systemic inflammation, contributing to endothelial dysfunction and atherosclerotic processes. The presence of heavy metals such as zinc and cadmium may amplify these effects, potentially increasing cardiovascular risk in exposed populations.

Given their environmental persistence and ability to cross biological barriers, TWPs function not only as particulate pollutants but as complex chemical vectors capable of systemic bio accumulation and multigenerational impact.

The Electric Vehicle Paradox.

The increased mass of electric vehicles; typically 20–30% greater than internal combustion counterparts results in proportionally higher tire wear and particle generation. EVs do not eliminate emissions. They simply transfer auto emissions from the exhaust pipe to the plant where the electricity is generated. They also exacerbate non-exhaust emissions from tires and brakes, with some analyses estimating TWP output up to 20% higher per kilometer traveled.

This shift represents a critical oversight in current regulatory frameworks, which primarily measure vehicular emissions through exhaust pipe metrics. As EV adoption accelerates globally, the total load of tire-derived particulates released into the environment is projected to rise substantially, offsetting some of the environmental health gains achieved through electrification. Addressing this paradox requires reconceptualizing “zero-emission” mobility to account for all lifecycle and non-exhaust sources of pollution. This includes the sourcing of raw earth material used in manufacturing as well as manufacturing.

Barriers to Recognition and Regulation

Several factors have contributed to the delayed recognition of TWP related health risks.

First, tire formulations are proprietary, limiting transparency and hindering toxicological assessment. Second, regulatory testing has historically emphasized exhaust emissions, leaving non-exhaust sources largely unmonitored.

Third, TWPs do not fit neatly into existing pollutant classifications. They are simultaneously particulates, microplastics, and chemical mixtures, complicating risk assessment and enforcement.

The diffuse nature of TWP dispersion further obscures causal attribution. Unlike industrial point of source pollutants, tire wear releases are ubiquitous and spatially distributed, making exposure quantification challenging. Further, the latency of chronic health outcomes, particularly neurodevelopmental effects, hinders epidemiological detection without targeted longitudinal studies.

Causal attribution of autism and other complex diseases to tire-derived pollutants remains a hypothesis and epidemiological and mechanistic work is still emerging.

Balancing Intervention with Sobriety and Engineering Reality.

While removing toxic additives like 6PPD may seem like an obvious next step, doing so without a proven substitute could lead to new and equally serious problems. 6PPD wasn’t added to tires by accident, it prevents the rubber from breaking down when exposed to ozone and heat. Without it, tires will crack, harden, or fail prematurely, increasing the risk of blowouts and accidents. Shorter tire lifespans would also mean higher manufacturing demand, more raw-material consumption, and ironically, greater overall particulate emissions as more tires wear out faster.

In other words, a well-intentioned ban or new law, could trade one form of harm for another (which seems to happen all too often). This is a reminder that every “solution” in human engineering carries consequences a few moves down the road (pun intended). The responsible path forward is to identify and validate safer functional alternatives first; other compounds, methods and materials that protect tire integrity without producing persistent or toxic byproducts.

And that’s all I have to say about that. I did not intend to say anything.