UBC Researchers Uncover Deadly Link Between Synthetic Turf and Coho Salmon

A groundbreaking study from the University of British Columbia (UBC) has exposed a hidden environmental threat lurking in Metro Vancouver's sports fields: artificial turf. Researchers discovered that runoff from these synthetic surfaces is releasing 6PPD-quinone (6PPD-Q), a highly toxic chemical derived from tire rubber, directly into stormwater systems. This pollutant is lethal to coho salmon (Oncorhynchus kisutch), a species already under pressure in urban waterways, at concentrations as low as 41 nanograms per liter—the median lethal concentration (LC50) for juvenile coho.

The findings, published in the journal Environmental Science: Processes & Impacts, highlight how everyday recreational infrastructure contributes to aquatic ecosystem decline. Led by PhD student Kate J. Moloney and supervised by Assistant Professor Rachel C. Scholes in UBC's Department of Civil Engineering, the research sampled infill material from 12 artificial turf fields across Metro Vancouver. What they found was alarming: even fields over a decade old continued leaching contaminants, acting as persistent point sources of pollution.

In one striking example, stormwater drainage from a monitored field reached 130.2 ng/L of 6PPD-Q—more than three times the lethal threshold for young coho salmon. This chemical, formed when N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), an antiozonant in tires, oxidizes, has been implicated in mass die-offs of coho in urban streams since its identification in 2020 near Puget Sound.

The Science Behind Crumb Rubber Infill and Its Toxic Leaching

Modern artificial turf relies on crumb rubber infill, ground from post-consumer vehicle tires, to provide cushioning and stability. An average field holds about 125 tonnes of this material—equivalent to roughly 20,000 tires. While recycling tires reduces landfill waste, the process mobilizes hazardous substances.

The UBC team's laboratory leaching experiments simulated rainfall on infill samples. Crumb rubber released significantly higher levels of 6PPD-Q, its parent compound 6PPD, zinc, and copper compared to alternatives like ethylene propylene diene monomer (EPDM) rubber or thermoplastic elastomer (TPE). Non-targeted analysis revealed 14 additional compounds, including the bioaccumulative dye leucomalachite green and plasticizers like di(2-ethylhexyl)phthalate (DEHP), an endocrine disruptor.

Stormwater samples collected during three rain events from three fields (aged 3.5 to 13.5 years) confirmed real-world release. Peaks occurred shortly after rain began: zinc at 30.3 µg/L, copper at 726.4 µg/L, and 6PPD-Q at levels far exceeding safe thresholds. Importantly, leaching did not diminish with age, suggesting fields remain hazardous for their full 10-15 year lifespan and beyond.

• Crumb rubber infill: High release of tire toxicants.
• Alternative infills (EPDM, TPE): Lower contaminant levels, but costlier and sometimes less durable.
• Annual release: Less than 1% of total 6PPD per field, ensuring long-term pollution.

Coho Salmon: A Canary in the Urban Waterway Coal Mine

Coho salmon, prized for their cultural and ecological value in British Columbia, are particularly vulnerable. Urban streams in Metro Vancouver serve as spawning grounds, but stormwater outfalls deliver untreated pollutants directly to these habitats. The UBC study notes that multiple fields draining into small watersheds could amplify concentrations, creating 'hotspots' deadly to juveniles.

Prior research established 6PPD-Q's potency: a 24-hour exposure at 41 ng/L kills 50% of hatchery-raised coho. Field measurements surpassing this underscore the risk. Heavy metals like zinc (toxic above 30 µg/L for salmonids) and copper exacerbate effects, disrupting gill function and osmoregulation.

The crisis echoes 'Dead of Autumn Syndrome' in Washington State, where tirewear particles from roads kill adult coho. Turf fields add a new vector, especially as Metro Vancouver expands recreational infrastructure ahead of events like the 2026 FIFA World Cup.

Metro Vancouver's Turf Landscape: Scale of the Problem

Metro Vancouver boasts hundreds of artificial turf fields at schools, parks, and community centers, prized for all-weather play amid rainy winters. Vancouver operates 12 out of 151 rectangular fields with turf; Surrey has 18 and plans more; Burnaby monitors closely. With fields lasting over a decade, cumulative runoff threatens local salmon runs.

The study was sparked by North Vancouver streamkeepers observing crumb rubber particles and dead coho near a turf field in late 2023. Stormwater pipes bypass treatment, dumping directly into creeks. As climate change intensifies storms, leaching events could surge.

Broader Canadian context: Similar fields proliferate in Toronto, Calgary, and Victoria. While B.C. leads salmon conservation, unchecked expansion risks fragile populations listed under Canada's Species at Risk Act.

Photo by Mathieu Deslauriers on Unsplash

Stakeholder Perspectives: From Cities to Conservationists

Municipal responses vary. Vancouver Park Board phased out crumb rubber, favoring inert EPDM. Surrey tests infill and uses catch basins. Burnaby collaborates with streamkeepers. All emphasize stormwater management but face budget constraints.

Conservation groups like the Pacific Salmon Foundation urge phase-outs. "Every time it rains, these fields release a mix of chemicals," warns Moloney. Scholes adds, "Our data can guide field design and treatment to protect ecosystems." Industry defends recycling benefits but eyes safer infills.

EU's microplastics ban on crumb rubber signals global shift; Canada may follow, balancing recreation with ecology.

Viable Alternatives: Balancing Play and Protection

Safer options exist, though trade-offs apply:

• EPDM rubber: Inert, low leaching; used in Vancouver.
• Cork or coconut fiber: Organic, biodegradable; freezes in cold climates.
• TPE/sand blends: Lower toxicants; higher cost (~2x crumb rubber).
• Natural grass with reinforcements: Hybrid systems reduce chemicals entirely.

Stormwater solutions shine: Bioretention cells (rain gardens) filter 90% of 6PPD-Q. UBC tests these, showing promise for retrofits. Cost-benefit analyses favor prevention over remediation.

Policy Pathways and Calls to Action

B.C. could mandate non-toxic infills, require treatment, or incentivize grass hybrids. Federal tire recycling programs need greener outlets. Schools and unis, major turf users, should audit fields.

UBC's work exemplifies higher education's role in sustainability. Explore environmental research positions or Canadian academic jobs tackling such challenges.

As Metro Vancouver weighs World Cup upgrades, evidence demands action. Protecting salmon safeguards biodiversity, fisheries, and First Nations rights.

UBC's Leadership in Urban Environmental Engineering

Scholes Lab pioneers stormwater toxicology, bridging engineering and ecology. This study builds on global 6PPD-Q research, informing policy. UBC's Okanagan campus tests turf alternatives; collaborations with municipalities accelerate solutions.

Higher education drives change: Student-led monitoring empowers communities. For aspiring researchers, UBC offers programs in civil engineering and environmental science.

Photo by Norbert Buduczki on Unsplash

Looking Ahead: Sustainable Recreation in Salmon Country

The UBC study spotlights a solvable crisis. With feasible fixes, Metro Vancouver can enjoy fields without sacrificing salmon. Ongoing monitoring, innovation, and policy will ensure urban growth harmonizes with nature.

Stakeholders unite: Reduce crumb rubber, treat runoff, innovate infills. Canada's commitment to wild salmon demands no less.