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RP10 Aquatic Ecotoxicology
(DRA-1117-746824) Analysis of tire rubber leachate with a bacterial mutagenesis assay.
Benevento, S1, Draper, A1, 1 Trinity College, Hartford, CT, USA
ABSTRACT- Rubber particles from automobile tires wear off with use and contribute to water pollution as they leach harmful chemicals into the environment. In an effort to examine the effects of these water-soluble chemicals, Salmonella typhimurium was used to assess the mutagenicity of tire rubber leachate. Tire tread particles were leached in hard water for 10 days at room temperature with constant agitation, filtered through a 0.45 m nylon membrane and stored at 4°C until use. The leachate was concentrated 10- and 100-fold with a C-18 solid phase extraction column, extracted into hexane, dried under N2 and reconstituted in DMSO. Bacterial mutagenesis assays using Ames strains TA 1535 and TA 1538 were performed according to Standard Methods. Briefly, bacteria were pre-incubated in nutrient broth for 12 hr at 37°C with shaking. Then, 0.1 ml of test material (in DMSO), 0.5 ml of rat liver S-9 mixture, and 2.5 ml of melted top agar were added. After 20 min additional incubation, the contents were vortexed, poured on minimal agar plates, and incubated at 37°C for 60 hr before being scored. Revertant colonies were counted and scored against negative control plates (DMSO), and diagnostic mutagens analyzed with each experiment served as positive controls. Evidence suggests that tire rubber leachate requires metabolism to induce mutation and may be mutagenic at elevated concentrations. While no mutagenesis was detected with unconcentrated tire rubber leachate, proportional mutagenesis was observed with 10:1 and 100:1 concentration. With a growing number of automobiles on the road there is a marked increase in the amount of tire rubber particles entering the environment: collecting on roadways as dust and eventually being washed into local waterways. Further work will be directed towards identifying the mutagenic chemical(s) in these particles and may suggest the elimination of toxic compounds in future tire production.
Key words: mutagenesis, tire rubber leachate, Salmonella mutagenesis assay
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