Tyre Pollution NZ 2025: The Hidden Emissions From Every Km You Drive
Tyre Pollution NZ: The Hidden Emissions From Every Km You Drive
Most Kiwi drivers think "vehicle pollution" = exhaust. But every time you accelerate, brake, and corner, your tyres shed microscopic particles of rubber and road material. Those particles don't disappear — they build up on roadsides, wash into stormwater, and some become airborne. Here's what it actually means for New Zealand.
⚡ TL;DR — The 60-Second Version
🛞 Tyres are a pollution source. As exhaust gets cleaner, "non-exhaust" emissions (tyre wear, brake wear, road dust) become the dominant source of traffic-related particulate pollution.
🇳🇿 NZ scale: A 2024 estimate suggests 6,500–15,500 tonnes of tyre tread wear is released annually — about 1.26–2.97 kg per person per year.
🌧️ Main pathway: Most tyre wear ends up on/near the road as dust; rain washes it into streams, harbours, and eventually the ocean.
✅ Biggest driver actions: Correct pressure, good alignment, healthy suspension, smooth driving, and avoiding unnecessary weight all reduce abnormal wear (and keep you safer).
⚠️ Key chemical: A transformation product of a common tyre antioxidant (6PPD) — 6PPD-quinone — has been linked to acute coho salmon mortality at very low concentrations in stormwater.
📋 What's Covered in This Guide
What "Tyre Pollution" Actually Means
"Tyre pollution" is shorthand for two related things:
- Particles: Bits of tyre tread (rubber + fillers) that abrade off in normal driving. Many particles also pick up road material, forming tyre and road wear particles (TRWP).
- Chemicals: Additives in tyres (antioxidants, accelerators, oils, metals like zinc) that can leach out of particles into water — especially in stormwater conditions.
Tyre pollution sits under the wider umbrella of "non-exhaust emissions" (tyre wear, brake wear, road surface wear, and re-suspended road dust). As tailpipe emissions reduce with cleaner engines and EV adoption, non-exhaust becomes a larger share of traffic-related particulate pollution.
| Traffic Emission Type | What It Is | Why It Matters |
|---|---|---|
| Exhaust | Tailpipe gases + particles | Heavily regulated; trending down per vehicle |
| Tyre wear | Tread abrasion + TRWP | Not eliminated by EVs; major microplastic pathway |
| Brake wear | Pad/disc dust | Regen braking can reduce this (EV advantage) |
| Road dust | Dust lifted back into air by traffic | Can dominate roadside PM in dry conditions |
How Much Tyre Wear Does New Zealand Produce?
Here's the uncomfortable truth: even if every car in NZ became electric tomorrow, tyre wear would still exist — because it's created by contact, not combustion.
Those numbers come from a 2024 NZ discussion paper estimating annual tyre tread wear using vehicle travel statistics and emission factors from international studies. The authors highlight that uncertainty is high, and NZ-specific emission factor measurements are needed (because our road surfaces, climate, terrain, and fleet mix differ from overseas datasets).
The Physics: Why Tyres Shed Particles
A tyre works by deforming. That deformation creates grip — but it also creates heat and abrasion. Every time the tread scrubs against the road (especially under braking, acceleration, cornering, and rough chipseal), you lose microscopic material.
Wear = Rate × Distance
Your total tyre wear emissions scale with (1) how quickly you wear the tread and (2) how far you drive. "Rate" is where pressure, alignment, weight, driving style, and tyre compound all matter.
Typical Emission Factors
European inventory guidance includes tyre wear particle estimates by vehicle type. For a passenger car, the total suspended particle (TSP) tyre wear factor is on the order of ~0.010–0.012 g/km, with a portion of that mass in the PM10 and PM2.5 ranges.
| Vehicle Type | Tyre Wear (TSP) | What This Means |
|---|---|---|
| Passenger car | ~0.01 g/km (≈ 10 g per 1,000 km) | Turns "invisible dust" into a number you can picture |
| PM10 / PM2.5 share | Not all is "fine" PM; large fraction is coarse | Most material deposits near roads, not in lungs |
Real-World "Wear Multipliers" You Can Control
Why: Frequent acceleration/braking = more tread shear + more fine particles.
Why: Less harsh shear events means less tread loss.
Why: More normal force + more heat = faster tread loss if unmanaged.
Where It Goes: Air vs Stormwater vs Soil
Tyre wear doesn't behave like exhaust. Exhaust particles are emitted into the air immediately. Tyre wear mostly lands on the road and roadside — then moves with wind, traffic turbulence, and rain.
The "Three Compartment" Model
| Where It Ends Up | What Happens Next | Why This Matters in NZ |
|---|---|---|
| Road + roadside soil | Builds up as dust; mixes with road-wear material | Much of the mass is coarse (10–350 µm), so deposits near roads |
| Stormwater | Rain washes particles into drains → streams → harbour | Urban NZ has lots of hard surfaces. Runoff carries tyre chemicals |
| Air (fine fraction) | Some particles stay airborne; inhalation exposure possible | NZ estimate suggests up to ~10% by mass may be <10 µm |
What's In Tyre Wear? Rubber + Metals + Chemical Additives
If tyre wear was "just rubber", it would still be a microplastic problem. But tyres are engineered chemical systems — polymers, reinforcing fillers, and a cocktail of additives designed to manage grip, durability, heat, ozone exposure, and manufacturing.
| Component | Examples | Environmental Impact |
|---|---|---|
| Rubber polymers | Natural + synthetic rubber blends | Particles fall into "microplastic" size ranges and persist |
| Reinforcing fillers | Carbon black, silica | Influence abrasion rate and how particles behave |
| Metals | Zinc (from ZnO), trace metals | Zinc can leach and affects plants and aquatic life |
| Antioxidants | 6PPD (common), transforms to 6PPD-quinone | Some transformation products highly toxic to certain species |
| Accelerators | DPG, benzothiazoles, HMMM | Detected in runoff; some persist and move through water |
The 6PPD-Quinone Problem: Stormwater + Fish
The single biggest reason tyre pollution exploded into mainstream environmental science recently is one compound: 6PPD-quinone.
Here's the chain:
- Tyres commonly contain 6PPD, an antioxidant used to protect rubber from ozone and reactive oxygen species.
- In the environment, 6PPD reacts with ozone and forms 6PPD-quinone.
- Tyre particles carrying these chemicals are washed by rain into streams and waterways.
This does not mean "all stormwater kills all fish everywhere". It means tyre-derived chemicals can be present in stormwater at concentrations that are biologically meaningful — and that stormwater management (and tyre chemistry) are now part of aquatic ecosystem protection conversations.
What Actually Reduces Tyre Pollution?
There's no single silver bullet. Tyre pollution is the result of kilometres travelled × wear rate × runoff transport. The best solutions work at multiple levels: driver behaviour, vehicle maintenance, urban design, and tyre chemistry.
Level 1: Driver + Vehicle (Fast Wins)
Level 2: City + Stormwater (Where the Big Wins Are)
Because stormwater is a major transport pathway, councils and infrastructure have leverage:
- Gully trap maintenance + targeted street sweeping (removes roadside dust before rain moves it)
- Stormwater treatment trains (sedimentation + filtration + bio-retention)
- Green infrastructure designed to capture and treat runoff (actively researched for tyre-related chemicals like 6PPD-quinone)
Level 3: Tyre Design + Regulation (The Long Game)
Internationally, regulators and researchers are increasingly focused on measuring and reducing non-exhaust emissions. The OECD notes that non-exhaust emissions are expected to dominate road transport PM emissions in coming years, and that mitigation will require policy and technical innovation beyond tailpipes.
Tyre Pollution Myths — Busted
Reality: EVs remove tailpipe emissions, but tyre wear still occurs (and can increase with vehicle mass). Non-exhaust emissions become a bigger share as exhaust drops.
Reality: Tyre wear includes synthetic polymers and a complex additive mix. Research reports 214+ tyre-associated chemicals, many leachable and mobile in water.
Reality: Overinflation can concentrate load on the centre tread and increase centre wear (shortening tyre life). The goal is correct pressure for even wear, safety, and longevity.
Reality: Road runoff picks up brake dust, tyre residue, oil, and heavy metals and transports them into waterways.
Reality: NZ-specific estimates exist and suggest thousands of tonnes per year of tyre tread wear released into the environment. Research focus is now on measuring NZ-specific emission factors and hotspots.
Frequently Asked Questions
It's the mix of rubber/road dust particles and tyre-related chemicals created when tyres wear, plus the pathways that move those materials into air and waterways.
A 2024 estimate suggests roughly 6,500–15,500 tonnes/year, about 1.26–2.97 kg/person/year, with light passenger vehicles around 45% of the total.
No. Much of the mass is coarse and deposits near roads (10–350 µm). A smaller fraction may remain airborne as respirable particles (<10 µm).
It's formed when a common tyre antioxidant (6PPD) reacts in the environment. Research identified 6PPD-quinone in stormwater and linked it to acute coho salmon mortality at very low concentrations.
Oceans are one endpoint, but roadsides and freshwater are major compartments too. A global estimate attributed ~28% of primary ocean microplastics to tyre abrasion.
Keep pressures correct, fix alignment/suspension issues, rotate tyres, drive smoothly, and avoid unnecessary weight. These reduce abnormal wear and extend tyre life.
Yes — especially by capturing roadside dust and treating stormwater before it reaches streams. EPA notes active research into treatment options for tyre-derived chemicals.
Absolutely. NZ-specific emission factors, real-world hotspot measurements, and chemical mixture effects are active research areas.
"If you can see abnormal wear on a tyre, you're looking at pollution you could have prevented — and money you didn't need to spend."
Sources & References
This guide is based on peer-reviewed research, government reports, and industry data. Key sources include:
- NZ Tyre Wear Estimates: Moores, J. & Pattinson, P. (2024). Tyre wear particle emissions in New Zealand: A discussion paper. Prepared for Ministry for the Environment.
- Global Microplastics: Boucher, J. & Friot, D. (2017). Primary Microplastics in the Oceans: A Global Evaluation of Sources. IUCN, Gland, Switzerland.
- 6PPD-Quinone Research: Tian, Z. et al. (2021). "A ubiquitous tire rubber-derived chemical induces acute mortality in coho salmon." Science, 371(6525), 185-189.
- Tyre Chemical Composition: Wik, A. & Dave, G. (2009). "Occurrence and effects of tire wear particles in the environment." Science of the Total Environment, 407(12), 3691-3700.
- European Emission Factors: EMEP/EEA Air Pollutant Emission Inventory Guidebook 2019 — Road Transport: Automobile tyre and brake wear.
- NZ Stormwater: NIWA. "Urban stormwater quality." National Institute of Water and Atmospheric Research.
- Non-Exhaust Emissions: OECD (2020). Non-exhaust Particulate Emissions from Road Transport: An Ignored Environmental Policy Challenge. OECD Publishing, Paris.
- US EPA: "6PPD and 6PPD-quinone." United States Environmental Protection Agency — Research on tyre-derived chemicals in stormwater.
