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Date Permissions Signed


Date of Award

Fall 2021

Document Type

Masters Thesis

Department or Program Affiliation

Environmental Science - Toxicology and Chemistry

Degree Name

Master of Science (MS)


Environmental Sciences

First Advisor

Sofield, Ruth M.

Second Advisor

Montaño, Manuel D.

Third Advisor

McIntyre, Jenifer K.


For this study seven tire groups (six used-tire groups and one new-tire group) of the same brand and model tire spanning manufacture year 2013 to 2018 were used. Tire particles were artificially created and baseline toxicity was measured using the eluate from unweathered tire particle groups through 96-hour acute toxicity tests using Americamysis bahia. These results were then compared to toxicity results from a subset of the same tire groups that were deployed in a marine environment for weathering. Toxicity of unweathered tire particle groups had an LC50 range of 1.97 to 3.51 g/L and the toxicity of weathered tire groups had an LC50 range of 3.67 to 12.09 g/L. These toxicities were found to span four distinct toxicity categories based on ratio tests of the LC50 values. Eluate from each test treatment was analyzed for metals by ICP-MS. Cu and Ni were the only metals found to be significantly lower after weathering. The concentrations of Cu, Ni, and Zn at the LC50s were correlated with their respective LC50s based on the tire wear particle concentrations. Cu and Ni had strong positive correlations showing an inverse relationship with toxicity, indicating that these metals likely do not contribute to toxicity but instead that the tires are the source of the metals. Zn concentrations showed no correlation and was at the approximate LC50 for Zn alone, indicating that it may be contributing to toxicity.




Western Washington University

OCLC Number


Subject – LCSH

Tires--Environmental aspects; Tires--Erosion; Microplastics--Toxicology; Shrimps--Effect of pollution on




masters theses




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