Evaluation of tire tread particle toxicity to fish using rainbow trout cell lines.

Tire and road wear particles (TRWP) resulting from tire abrasion while driving raise concerns due to their potential contribution to aquatic toxicity. Our study aimed to assess cryogenically milled tire tread (CMTT) particle toxicity, used as a proxy for TRWP, and associated chemicals to fish using two Rainbow Trout (Oncorhynchus mykiss) cell lines representing the gill (RTgill-W1) and the intestinal (RTgutGC) epithelium. CMTT toxicity was evaluated through several exposure pathways, including direct contact, leaching, and digestion, while also assessing the impact of particle aging. Following OECD TG249, cell viability was assessed after 24 h acute exposure using a multiple-endpoint assay indicative of cell metabolic activity, membrane integrity and lysosome integrity. In vitro EC50 values for the fish cell lines exceeded river TRWP concentrations (2.02 g/L and 4.65 g/L for RTgill-W1 and RTgutGC cell lines, respectively), and were similar to in vivo LC50 values estimated at 6 g/L. Although toxicity was mainly driven by the leaching of tire-associated chemicals, the presence of the particles contributed to the overall toxicity by inducing a continuous leaching, highlighting the importance of considering combined exposure scenarios. Aging and digestion conditions were also found to mediate CMTT toxicity. Thermooxidation resulted in a decreased chemical leaching and toxicity, while in vitro digestion under mimicked gastrointestinal conditions increased leaching and toxicity. Specific chemicals, especially Zn, 2-mercaptobenzothiazole, 1,3-diphenylguanidine, and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) were identified as contributors to the overall toxicity. Although 6PPD-quinone was detected in CMTT digestate, cytotoxicity assays with RTgill-W1 and RTgutGC cell lines showed no toxicity up to 6 mg/L, supporting the notion of a specific mode of action of this chemical. This study provides insights into the toxicological mechanisms induced by tire particles and their associated chemicals and can help in the evaluation of potential risks to aquatic life associated with TRWP.

[Ab-interno sclerostomy with the excimer laser via a quartz fiber in albino rabbits]. / Ab-interno Sklerostomie mit dem Excimerlaser über Quarzfaser am Albinokaninchen.

After attempting to induce experimental glaucoma in 20 albino rabbits by topical administration of 0.1% dexamethasone, ab-interno sclerostomy with an excimer laser at 308 nm via a quartz fiber was performed in one eye of each animal. Preoperatively, the sclera was stained with a UV-absorbing drug (sulfisomidine) in 10 rabbits; to shield the lens from scattered radiation, another UV absorber (fluorescein) was injected additionally into the anterior chamber. The other 10 rabbits were operated on without pretreatment. A full-thickness sclerostomy was performed in all animals. Most of the eyes upon operated showed minimal inflammation in the first few postoperative days. The intraocular pressure in the operated eyes was reduced compared to the fellow eye for about 3 months. Histology showed a 50-microns broad, smooth, thermally damaged zone at the edges of the sclerostomy. Clinical and histological investigation showed no evidence of UV-induced damage on the lens or retina in either group. Application of the UV absorber led to a significant decrease in the number of pulses required to perforate the sclera, but had no influence on the clinical history.