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Date Permissions Signed
Date of Award
Master of Science (MS)
Sofield, Ruth M.
Hecker, Marcus (College teacher)
Tire-wear particles (TWPs) are considered among the largest contributors of microplastics to the environment. They are subject to break-down due to environmental weathering, which allows for potentially toxic chemicals to be released from and sorbed onto the particles. In this study, leachate generated from “weathered” and “un-weathered” TWPs were used for sublethal toxicity tests with Americamysis bahia. Organisms were exposed for 2, 4, and 6 days and the effects endpoints included changes in respiration rate and molecular responses (i.e., changes in the abundance of transcripts after 4 days of exposure). A threshold for stimulated respiration rate was detected for weathered leachate on day 2 only between 0.133 and 0.67 g/L TWP leachate. For the un-weathered leachate, the threshold was on days 4 and 6 and was between 0.54 and 1.08 g/L TWP leachate. There were dysregulated contig sequences, in all tested concentrations for weathered (0.67, 1.34, and 2.68 g/L) and un-weathered (0.27, 0.54, and 1.08 g/L) TWP leachates; the contigs had sequences orthologous to specific gene descriptions in arthropods and were considered significantly dysregulated at an FDR ≤ 0.05 and |log2FC| ≥ 1. There were 80 dysregulated contigs across all tested weathered leachate concentrations and 139 dysregulated contigs across all tested un-weathered concentrations. Upregulated contigs at 2.68 g/L for weathered and 1.08 g/L for un-weathered leachates showed enrichment compared to the de novo reference transcriptome; this coincided with a significant respiration stimulation observed at 1.08 g/L in the un-weathered leachate. There were five enriched pathways in the weathered group and 10 enriched pathways in the un-weathered group; serine hydrolase, serine-type peptidase, and peptidase activity were enriched in both groups. Many contig sequences mapped to gene descriptions that regulated physical body structure, inflammatory response, and mediated protein-protein interactions, signifying that TWP leachate exposure disrupts many internal molecular processes in A. bahia.
Tire particle leachate, respiration, transcriptomics, differential expression
Western Washington University
Subject – LCSH
Tires--Erosion; Microplastics--Environmental testing; Leachate--Toxicology; Mysidae--Effect of pollution on; Nucleotide sequence
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Leazer, Karrin, "Tire-wear-particle leachate toxicity to Americamysis bahia: analysis of sublethal and molecular effects" (2022). WWU Graduate School Collection. 1132.