Car tyre chemical liable for salmon kill – researchers

Researchers at the University of Toronto Scarborough helped discover a chemical by-product in tyres that may be responsible for killing wild salmon.

The chemical by-product, which a team of researchers in the US found, is likely responsible for killing wild coho salmon and is making headlines across the world, was first identified in Professor and chemist Andre Simpson’s lab at U of T Scarborough.

Simpson and his team were able to map out the structure of the chemical based on two tiny, 10-mcg samples sent to them by the study’s lead investigator Ed Kolodziej, an associate professor at the University of Washington. 

According to Simpson, the US team had isolated and broken the chemical soup from tyres down to the sub-component causing the toxicity, but they didn’t know what the individual chemical was. Over the course of six weeks, Simpson and his team were able to map out the chemical’s structure using nuclear magnetic resonance (NMR) technology. 

Simpson’s team was able to map out every single bond in the molecule and worked out how they linked together. Then, the team ran it through a database and realized it was a new chemical structure.

The chemical 6PPD is commonly used in automobile tyres to make them last longer, but as the tyre tread breaks down it leaves behind small microplastics on the road. As 6PPD reacts with ozone it becomes a different chemical by-product, known as 6PPD-quinone, that dissolves easily in water and shows greater stability, meaning it can easily enter aquatic environments and stay there for an extended period.      

Researchers found the chemical, which is highly toxic to coho salmon, in roadway runoff at sites across the west coast of the US. In recent years, scientists have been trying to figure out why the fish have been turning up dead in large numbers after heavy rain during the fall when the salmon swim inland to spawn.  

Kolodziej explained that they were able to identify the highly toxic chemical from a mix of 2,000 chemicals. This one highly toxic kills large fish quickly and is probably found on every single busy road in the world. The researchers say more work needs to be done to see if this chemical is toxic to other fish and aquatic wildlife in general.