Exposure of marine invertebrates to car tire rubber: Uptake of rubber particles and related organic chemicals

Abstract

Car tire rubber particles (CTRPs) are a major source of microplastic pollution to the environment, originating from abrasion during driving or the use of crumb rubber granulates made of discarded tires. However, large knowledge gaps remain regarding the distribution and presence of CTRPs in marine environments and interaction with marine organisms. The aims of this thesis were to investigate the uptake of CTRPs and associated organic chemicals in marine invertebrates exposed to car tire rubber (CTR), and to assess the use of these chemicals as markers of CTRP exposure in their environment. To do so, we used blue mussels (Mytilus edulis), shore crabs (Carcinus maenas) and edible crabs (Cancer pagurus) exposed to CTRPs. First, blue mussels (n = 60) were experimentally exposed for seven days to low or high concentrations of a CTRP mix (with a tenfold increase), followed by a depuration period of seven days and sampled throughout the experiment. In addition, crabs were sampled in situ in reference sites (Kristiansand) and in a highly contaminated site, by Norway’s largest car tire shredding facility in Frierfjorden (Southern Norway) were investigated for ingested rubber particles in stomachs (n = 49). Tissues of mussels and crab gills (n = 33) were analyzed for targeted CTRP-related compounds, specifically 6PPD and its transformation product 6PPD-quinone using gas chromatography/mass spectroscopy (GC/MS). Seven CTRP-related chemicals (6PPD, CPPD, DPPD, TPPD, DTPD, C21H26N2 and C23H26N2) were found in all experimentally exposed blue mussels, indicating that all of them ingested CTRPs and/or took up leachates from their surrounding water. We reported uptake of all associated chemicals in highly exposed individuals, except for 6PPD-Q. Moreover, our data indicated the accumulation of some chemicals during exposure (TPPD and (DTPD), as well as a linear relation between the exposure dose and the 6PPD uptake in mussel tissue. DTPD was detected in high concentrations and decreased slowly in mussels post-depuration and appears as a promising candidate marker in blue mussels for CTRPs in surrounding environments. While no large CTRPs (> 0.3 mm) were detected in wild crabs, 6PPD was detected at similar concentrations in gill tissue of both species from all sites, further highlighting gills to be a useful tissue to detect 6PPD. Overall, our study emphasizes that blue mussels and both crab species can be prime monitoring candidates for exposure to CTRP contamination in the environment. Their use as biomonitors of CTRP exposure is enhanced by their ecological characteristics such as the sessility of blue mussels and the robustness of crabs towards heavily polluted waters in addition to being both of relevance for human consumption.