Pollution washed from roads into waterways in California could threaten endangered coho salmon and steelhead trout, with a new study finding high levels of a chemical linked to tyre-wear in habitats where the fish live and spawn.
Researchers found that the pollutant, known as 6PPD-quinone, at levels known to cause harm to aquatic life in most water samples collected around the San Francisco Bay area and nearby parts of the Central California coast.
The chemical forms when 6PPD, a substance used to protect rubber tyres, reacts with ozone in the air – which it does by design, to pre-empt ozone causing damage to the rubber itself.
Tyre debris and the resulting pollutant can then be carried into streams and rivers by wind and rain.
Campaign group Earthjustice are currently pressing the US EPA to regulate the chemical under the Toxic Substances Control Act.
The research team, led by Ed Kolodziej, collected water samples from six road outfalls, 14 creeks and rivers and two estuaries during a rainstorm.
They found that 78% of samples exceeded the US Environmental Protection Agency’s value for the potential to cause acute harm to aquatic organisms. In 69% of samples, concentrations were higher than levels considered lethal to half of juvenile coho salmon exposed for 24 hours.
Pollutant levels tended to be higher in creeks near heavy traffic and substantially lower in estuaries, suggesting that proximity to busy roads plays an important role in contamination.
Other several fish species vulnerable to the chemical include brook, rainbow and steelhead trout.
Kolodziej, the study’s corresponding author, said: ‘These species are protected under the Endangered Species Act, and these are their most vulnerable and high-risk habitats.’
One creek had undergone extensive habitat restoration but also recorded some of the highest pollutant levels in the study.
‘A great habitat with toxic water quality makes the problem worse. You are creating an ecological trap for the fish,’ Kolodziej said.
The researchers say habitat restoration must therefore be accompanied by measures to improve water quality, particularly in areas designated as critical habitats for threatened and endangered species.
Potential solutions include treating stormwater runoff in heavily trafficked areas and developing tyres made with materials that are less toxic or non-toxic to the environment.
Kolodziej said: ‘6PPD-quinone is not the only harmful component of roadway runoff, so finding scalable and cost-effective solutions is important.’
Photo: Leo_Visions
