Preliminary Research Sheds Light on Proper Analysis and Sample Handling for the Tire-Derived Contaminants 6PPD and 6PPD-quinone
stormwater runoff
Tire and road wear particles have been shown to cause acute effects to sensitive aquatic animals and degrade their habitats. U.S. Geological Survey (USGS) scientists developed methods to accurately identify aquatic compounds, such as 6PPD and 6PPD-quinone, that can cause acute mortality events in coho salmon (Oncorhynchus kisutch).
6PPD is an antioxidant added during the production of tires to prevent them from degrading and cracking when exposed to ozone in the atmosphere. This reaction protects the tire, ensuring driver safety, but also transforms 6PPD into the compound 6PPD-quinone. During normal driving conditions, friction causes the accumulation of tire particles and chemicals on and around roads. These tire and road wear particles contain rubber and roadway materials. During stormwater runoff events these particles and chemicals, including 6PPD-quinone, are washed from the roadways and urban environments into the adjacent streams and other surrounding ecosystems.
Populations of coho salmon and other salmon off the western coast of the United States and Canada are at an all-time low. Previously, the population decline was attributed to climate change, freshwater habitat degradation, and fishing pressure. In highly urbanized watersheds, however, coho salmon population declines were linked to heightened mortality induced by toxic urban stormwater runoff. Scientists determined that, during these urban stormwater runoff events, 6PPD-quinone concentrations can exceed acute (short-term) toxicity thresholds for several salmonid species. Consequently, the potential role of 6PPD-quinone in the coho salmon population declines in the Pacific Northwest is an area of intense scientific study.
To accurately assess 6PPD-quinone effects on coho salmon and other sensitive species, USGS scientists experimented to inform best practices and accurate results for 6PPD-quinone sampling and analysis, including determining laboratory holding times, bottle material, headspace, and filter materials. In addition, the first reconnaissance of 6PPD and 6PPD-quinone in surface waters across the United States was completed to understand 6PPD-quinone stream concentrations better. In total, 526 samples were analyzed from agricultural, urban, industrial, and forested areas from 94 sites across the United States during high and low streamflow conditions.
It was determined that the chemical and microbial complexity of stormwater resulted in a range of stabilities for 6PPD-quinone. Results indicated that glass bottles are recommended for collection and 6PPD-quinone was stable for as many as 75 days in the refrigerator (5 degrees Celsius) with or without headspace in the sample bottle. Scientists also tested a range of filter materials to minimize interactions and losses during water sample filtration. They determined that binder-free borosilicate glass fiber and glass microfiber fiber resulted in the highest 6PPD-quinone recovery during sample filtration.
In the 526 samples collected across the United States, 6PPD was not detected in any sample, and the highest 6PPD-quinone concentrations, which were above the lethal concentration for coho salmon (lethal concentration at which 50% of the animals died was determined to be around 41 to 95 nanograms per liter), occurred only during stormwater runoff events. Specifically, water collected from urban-affected stormwater locations had the highest observed concentrations of 6PPD-quinone.
The final method for 6PPD-quinone minimized sorption and loss during sample collection in the field and optimized method performance to accurately assess 6PPD-quinone in water. Results also highlighted the importance of collecting water samples in urban areas during runoff conditions following storm events near ecologically important habitat or nursery grounds for sensitive fish species.
This study was supported by the USGS Ecosystems Mission Area, through the Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), as well as the Kansas Water Science Center and Western Fisheries Research Center. For information on previous studies, please see reports discussing establishing in vitro models to assess the toxicity of 6PPD-quinone by Greer and others (2023a), and more detail on how 6PPD-quinone induces mortality in coho salmon in Greer and others (2023b).
Tire and road wear particles have been shown to cause acute effects to sensitive aquatic animals and degrade their habitats. U.S. Geological Survey (USGS) scientists developed methods to accurately identify aquatic compounds, such as 6PPD and 6PPD-quinone, that can cause acute mortality events in coho salmon (Oncorhynchus kisutch).
6PPD is an antioxidant added during the production of tires to prevent them from degrading and cracking when exposed to ozone in the atmosphere. This reaction protects the tire, ensuring driver safety, but also transforms 6PPD into the compound 6PPD-quinone. During normal driving conditions, friction causes the accumulation of tire particles and chemicals on and around roads. These tire and road wear particles contain rubber and roadway materials. During stormwater runoff events these particles and chemicals, including 6PPD-quinone, are washed from the roadways and urban environments into the adjacent streams and other surrounding ecosystems.
Populations of coho salmon and other salmon off the western coast of the United States and Canada are at an all-time low. Previously, the population decline was attributed to climate change, freshwater habitat degradation, and fishing pressure. In highly urbanized watersheds, however, coho salmon population declines were linked to heightened mortality induced by toxic urban stormwater runoff. Scientists determined that, during these urban stormwater runoff events, 6PPD-quinone concentrations can exceed acute (short-term) toxicity thresholds for several salmonid species. Consequently, the potential role of 6PPD-quinone in the coho salmon population declines in the Pacific Northwest is an area of intense scientific study.
To accurately assess 6PPD-quinone effects on coho salmon and other sensitive species, USGS scientists experimented to inform best practices and accurate results for 6PPD-quinone sampling and analysis, including determining laboratory holding times, bottle material, headspace, and filter materials. In addition, the first reconnaissance of 6PPD and 6PPD-quinone in surface waters across the United States was completed to understand 6PPD-quinone stream concentrations better. In total, 526 samples were analyzed from agricultural, urban, industrial, and forested areas from 94 sites across the United States during high and low streamflow conditions.
It was determined that the chemical and microbial complexity of stormwater resulted in a range of stabilities for 6PPD-quinone. Results indicated that glass bottles are recommended for collection and 6PPD-quinone was stable for as many as 75 days in the refrigerator (5 degrees Celsius) with or without headspace in the sample bottle. Scientists also tested a range of filter materials to minimize interactions and losses during water sample filtration. They determined that binder-free borosilicate glass fiber and glass microfiber fiber resulted in the highest 6PPD-quinone recovery during sample filtration.
In the 526 samples collected across the United States, 6PPD was not detected in any sample, and the highest 6PPD-quinone concentrations, which were above the lethal concentration for coho salmon (lethal concentration at which 50% of the animals died was determined to be around 41 to 95 nanograms per liter), occurred only during stormwater runoff events. Specifically, water collected from urban-affected stormwater locations had the highest observed concentrations of 6PPD-quinone.
The final method for 6PPD-quinone minimized sorption and loss during sample collection in the field and optimized method performance to accurately assess 6PPD-quinone in water. Results also highlighted the importance of collecting water samples in urban areas during runoff conditions following storm events near ecologically important habitat or nursery grounds for sensitive fish species.
This study was supported by the USGS Ecosystems Mission Area, through the Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), as well as the Kansas Water Science Center and Western Fisheries Research Center. For information on previous studies, please see reports discussing establishing in vitro models to assess the toxicity of 6PPD-quinone by Greer and others (2023a), and more detail on how 6PPD-quinone induces mortality in coho salmon in Greer and others (2023b).