Few drivers consider that their tires wear down over time—but that worn rubber often ends up polluting rivers, lakes, and even the ocean. Shockingly, tire wear particles now account for about 45% of all microplastics found in both terrestrial and aquatic environments worldwide.
Each time a vehicle moves, its tires shed microscopic particles of synthetic rubber. This situation is common on urban roads and highways with frequent braking and acceleration. Rain then washes these particles into ditches and storm drains. These drains eventually lead to streams, rivers, and oceans. They are filled with aquatic life and food sources.
Tire particles carry toxic additives like 6PPD. It is a common chemical used to prevent rubber degradation. 6PPD breaks down into 6PPD-Q, which is an extremely harmful compound. In one 2020 study, more than half of the coho salmon in Washington died when returning to spawn. They were exposed to 6PPD-Q in the water systems.
These chemicals are not just dangerous to fish. Studies have found 6PPD-Q in the urine of humans, raising growing concerns over long-term health effects on organs like the liver and kidneys.
TIRE PARTICLES ARE ALSO AIRBORNE, ESPECIALLY NEAR ROADS
It’s not just water at risk—tire wear particles can also become airborne. As a result, people and animals near busy roadways face potential long-term respiratory or systemic health issues.
This silent pollution source affects both urban and rural communities. Often, there are no visible signs until serious environmental or health problems arise.
In Oxford, Mississippi, researchers from the University of Mississippi collected over 30,000 tire particles from just 24 liters of stormwater runoff following two rainstorms. Concentrations are expected to be even higher in heavy traffic zones. In these areas, vehicle density and tire wear are significantly greater.
Why Filtering Stormwater Is the Most Promising Solution Right Now
Since tire manufacturers claim there’s no current replacement for 6PPD, intervention at the waterway level is a more immediate and effective option.
That’s where biofilters come in—natural, low-cost filtration systems using pine wood chips and biochar made from agricultural waste like rice husks.
BIOFILTERS MADE FROM PLANT WASTE REMOVE UP TO 90% OF TIRE PARTICLES
Researchers designed a filtration sock containing wood chips and biochar and placed it at a storm drain outlet. The results were remarkable.
After two storm events, water tested after passing through the biofilter contained up to 90% fewer tire wear particles. This proves these filters’ powerful potential.
WHY BIOCHAR AND WOOD CHIPS WORK SO EFFECTIVELY
Biochar has a porous structure and large surface area, allowing it to trap even the tiniest tire particles. It’s stable, low-cost, and highly absorbent.
Wood chips, rich in organic compounds, also remove chemical pollutants. Their natural, fibrous texture helps snare particles before they enter waterways.
SCALING THE SOLUTION: CHALLENGES AND LONG-TERM MONITORING
While promising, biofilters need ongoing maintenance, including proper disposal and eventual replacement as contaminants build up inside them over time.
Additionally, raw agricultural waste (not processed into biochar) may introduce its own organic pollutants, so sourcing and preparation remain crucial.
BIOFILTERS COULD BE A GAME-CHANGER IN POLLUTION CONTROL
With plastic pollution harming fish, ecosystems, and potentially human health, this simple, scalable approach offers communities a powerful line of defense.
By repurposing agricultural waste into sustainable filtration, we can dramatically reduce the microplastic load reaching our rivers, oceans, and food systems. When it comes to clean water, sometimes the best solution is rooted in nature.
