Event Details

Speaker: Dr. David Soucek, U.S. Geological Survey

Abstract: The tire rubber antioxidant 6PPD and its transformation product 6PPD-quinone (6PPDQ) have garnered much research attention since the latter was identified as the causative agent of urban runoff mortality syndrome for Coho Salmon in the Pacific northwest of the United States. Fewer than 10 species, all within the fish family Salmonidae, have been shown to be sensitive to 6PPDQ, while several fish and invertebrates are sensitive to the parent compound. USGS Columbia Environmental Research Center (CERC) has been investigating the effects of 6PPD and 6PPDQ on sensitive invertebrate species including the freshwater mussel and the mayfly. Both species were added to the list of those not sensitive to 6PPDQ at concentrations below solubility limits; however, in toxicity tests with 6PPD, there was evidence that the degradation of this tire wear compound produced unknown transformation products that caused mortalities in both species. CERC is also investigating the time-course and latency of 6PPDQ toxicity to sensitive salmonid species. While several studies have demonstrated the sensitivity of Coho Salmon, Rainbow Trout, and Brook Trout to 6PPDQ, the data are not all ideal for the development of Ambient Water Quality Criteria. Our aim was to address some of these data quality issues while also investigating differences among the species in acute effect concentrations over time. While most mortality for Coho Salmon and Brook Trout occurred early in the exposure period, Rainbow Trout continued to be affected throughout the four-day exposure. We did not observe any indication of latent toxicity when the surviving organisms were moved to clean water and observed for one-week post-exposure. We also evaluated tissue concentrations of 6PPDQ in these three species and noted differences in bioaccumulation factors. Our data illustrate the ephemeral nature of the 6PPDQ effects and will assist with the development of protective criteria for sensitive species.