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Thesis
EVALUATION OF THE RELATIVE ACUTE TOXICITY OF PPD ANTIOZONANT CHEMICALS AND THEIR TRANSFORMATION PRODUCTS ON COHO SALMON (ONCORHYNCHUS KISUTCH)
Washington State University
Master of Science (MS), Washington State University
05/2025
DOI:
https://doi.org/10.7273/000007407
Abstract
6PPD, a critical component of automobile tires, reacts with ozone in the environment to prevent rubber from cracking. The identification of 6PPD-quinone (6PPDQ), a transformation product of 6PPD, as the probable causal toxicant of pre-spawn mortality syndrome in coho salmon (Oncorhynchus kisutch) has led to increased efforts to find an alternative for 6PPD use in tires. Other chemicals in the PPD family are at the top of the priority list in the search for alternatives because they are likely to provide a similar antiozonant property. However, little is known about the toxicity of the PPD compounds and their transformation products, particularly to aquatic animals. In this study, the acute aquatic toxicity of five chemicals in the PPD family: 6PPD, 7PPD, 77PD, 44PD, and IPPD to coho salmon was investigated. Coho salmon were exposed to the PPD compounds for 24 hours to estimate median lethal concentrations (LC50s), based on the timeline of acute mortality of coho exposed to 6PPDQ. The relative toxicities of the parent compounds (LC50 ± 95% CI) were: 77PD (159 ± 28 μg/L), 44PD (202 ± 58 μg/L) > 6PPD (519 ± 95 μg/L), 7PPD (706 ± 123 μg/L) > IPPD (1113 ± 103 μg/L). 6PPD, 7PPD, and IPPD were selected to be ozonated using a novel gas-phase ozonation method that allows for large masses (>100mg) of PPD to be ozonated at once. Upon ozonation, each parent compound formed a respective quinone. The ozonated eluents exhibited significantly increased toxicity compared to the parent compounds. Of the ozonated eluents, 6PPD was the most toxic, followed by IPPD, with 7PPD being the least toxic. This preliminary investigation into the toxicity of PPDs on coho salmon has taken the critical first steps in exploring alternatives to 6PPD. Substantial additional research is required to find a safer antiozonant for use in tires.
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Details
- Title
- EVALUATION OF THE RELATIVE ACUTE TOXICITY OF PPD ANTIOZONANT CHEMICALS AND THEIR TRANSFORMATION PRODUCTS ON COHO SALMON (ONCORHYNCHUS KISUTCH)
- Creators
- Caitlin Anne Lawrence
- Contributors
- Jenifer McIntyre (Chair)Allan Felsot (Committee Member)John Stark (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of the Environment (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 67
- Identifiers
- 99901220470401842
- Language
- English
- Resource Type
- Thesis