Bioaccessibility of Organic Compounds Associated with Tire Particles Using a Fish In Vitro Digestive Model: Solubilization Kinetics and Effects of Food Coingestion

Abstract

Tire and road wear particles (TRWP) account for an important part of the polymer particles released into the environment. There are scientific knowledge gaps as to the potential bioaccessibility of chemicals associated with TRWP to aquatic organisms. This study investigated the solubilization and bioaccessibility of seven of the most widely used tire-associated organic chemicals and four of their degradation products from cryogenically milled tire tread (CMTT) into fish digestive fluids using an in vitro digestion model based on Oncorhynchus mykiss. Our results showed that 0.06−44.1% of the selected compounds were rapidly solubilized into simulated gastric and intestinal fluids within a typical gut transit time for fish (3 h in gastric and 24 h in intestinal fluids). The environmentally realistic scenario of coingestion of CMTT and fish prey was explored using ground Gammarus pulex. Coingestion caused compoundspecific changes in solubilization, either increasing or decreasing the compounds' bioaccessibility in simulated gut fluids compared to CMTT alone. Our results emphasize that tire-associated compounds become accessible in a digestive milieu and should be studied further with respect to their bioaccumulation and toxicological effects upon passage of intestinal epithelial cells.

Chemical characteristics, leaching, and stability of the ubiquitous tire rubber-derived toxicant 6PPD-quinone

“…The solvent extractable 6PPDQ measured here aligned well with reports by Masset et al (14 mg 6PPDQ per gram cryogenically milled tire tread). 55 These data indicate that ∼46% of the total surcial 6PPDQ mass was water leachable over 6 hours. Note here that these estimates do not consider formation of additional 6PPDQ upon the continued 6PPD reaction with ozone or long-term TMP dynamics.…”

Environmental Occurrence and Toxicity of 6PPD Quinone, an Emerging Tire Rubber-Derived Chemical: A Review

“…Furthermore, limited studies have been conducted on investigating the toxicity of 6PPDQ on freshwater crustaceans (e.g., Daphnia magna and Hyalella azteca), 60 fish larvae, 53 and also in vitro studies. 61,62 Of all the fish species investigated for their susceptibility to 6PPDQ, Oncorhynchus kisutch (Coho salmon) has been the subject of the most extensive research due to its high sensitivity. An approximate median lethal concentration (LC 50 ) of 800 ng/L was initially estimated for Coho salmon; 5 however, more recently this LC 50 was updated to 95 ng/L.…”

“…Since the identification of 6PPDQ in 2020, worldwide research has focused on the potential effects of 6PPDQ on aquatic life, particularly various fish species ,− (Supporting Information: Acute lethality (LC50) in fish (adult and larvae) species during exposure to 6PPDQ (Table S2)). Furthermore, limited studies have been conducted on investigating the toxicity of 6PPDQ on freshwater crustaceans (e.g., Daphnia magna and Hyalella azteca ), fish larvae, and also in vitro studies. , …”

Inhalation of climbing shoe particles is highly relevant for the human exposure to rubber-derived chemicals in indoor facilities

“…These results suggest that, as in other rubber products, 2SH-BTZ is used as a vulcanization accelerator during the curing process 26 . Other benzothiazoles are also present and are typically considered to be impurities or degradation products 21,27 . Unlike benzothiazoles, DPG and aniline were not detected in every shoe sample, with concentrations ranging from <LOQ to 814 µg/g and <LOQ to 225 µg/g, respectively.…”