Every rainstorm washes salmon-killing chemicals from Vancouver's artificial turf into local streams

The project started with dead fish. In late 2023, streamkeepers in North Vancouver contacted researchers at the University of British Columbia after noticing crumb rubber washing off a nearby artificial turf field. Dead coho salmon had been found in an adjacent stream. The connection was not proven, but the suspicion was straightforward: the same chemical known to leach from tire particles on roads was probably leaching from the 125 tonnes of ground-up tires covering the playing field next door.

The researchers decided to test it. What they found, published in a new study, confirmed the worst-case scenario - and revealed that the problem does not fade with time.

12 fields, one consistent problem

The UBC team, supervised by civil engineering assistant professor Rachel Scholes, collected infill samples from 12 turf fields across Metro Vancouver - nine with traditional crumb rubber infill and three using alternative materials. They analyzed which chemicals leached into water and also collected drainage from one operating field during three rainstorms.

The target chemical was 6PPD-quinone, a transformation product of 6PPD, a rubber preservative added to virtually all tires. When 6PPD reacts with ozone in the environment, it produces 6PPD-quinone, which is acutely toxic to coho salmon. Research from the University of Washington identified this chemical in 2020 as the cause of mass coho die-offs in urban streams across the Pacific Northwest.

The crumb rubber fields consistently released 6PPD-quinone. The alternative-material fields released fewer contaminants. But the critical finding was about age: drainage from one monitored field showed 6PPD-quinone concentrations exceeding lethal thresholds for juvenile coho salmon even though the field's infill was more than six years old.

"An average turf field contains about 125 tonnes of crumb rubber, roughly 20,000 tires," said Katie Moloney, a PhD student in environmental engineering and lead researcher. "With fields typically lasting a decade or more, they can become long-term sources of tire-derived pollution entering stormwater pipes, and ultimately fish-bearing waterways - frequently without treatment."

A chemical cocktail beyond 6PPD-quinone

The researchers also identified numerous compounds not listed in regulatory inventories of tire ingredients. Some may come from chemicals transferred by field users - sunscreen, sports drinks, cleaning products - and from weather-driven chemical changes in the rubber over time. Heavy metals including zinc and copper, both harmful to aquatic life, were detected consistently across the crumb rubber fields.

"Every time it rains, these fields release a mix of chemicals into the drainage system," Moloney said. The problem is not a single toxin but a complex and poorly characterized chemical mixture entering waterways with each storm event.

Treatment is feasible but not happening

Unlike tire particles shed from moving vehicles across thousands of miles of roadway, turf field drainage flows through fixed pipe networks. That makes treatment technically feasible. A 2023 study from the same UBC group demonstrated that passing stormwater through a planted soil filter can reduce 6PPD-quinone concentrations roughly 10-fold.

The problem is that most turf field drainage currently receives no treatment at all. Stormwater flows directly from the field into municipal systems and, in many cases, into fish-bearing streams. Installing filtration systems would add cost to field construction and maintenance, but the engineering is not novel.

No easy substitutes

Switching away from crumb rubber infill is one obvious response, but it introduces its own complications. Alternative infills - including cork, coconut fiber, and engineered thermoplastics - released fewer contaminants in the study. But they tend to be more expensive, and some natural materials like cork can freeze in cold climates, limiting year-round play.

There is also a recycling paradox. Crumb rubber infill is one of the main markets for recycled tires. Eliminating it raises questions about what happens to the millions of tires currently diverted from landfills through turf production. The European Union has already banned crumb rubber sales under broader microplastics regulations, setting a phaseout in motion, but alternative tire recycling pathways at that scale do not yet exist.

For the salmon populations of the Pacific Northwest - already stressed by habitat loss, warming waters, and declining ocean conditions - the additional pressure from tire-derived chemicals in urban streams is one more insult in a long list. The difference with turf fields is that the source is fixed, the drainage is contained, and treatment technology exists. Whether communities will invest in implementing it is a policy question, not a scientific one.