Impact of Pristine and Weathered Environmentally Relevant Multi-Tire Mixture on the Model Estuarine species Fish Menidia beryllina and Mysid shrimp Americamysis bahia

The rapid increase in plastic production and inadequate waste management are transforming the world’s oceans into a repository for plastic waste. Million tons of plastic enter the oceans every year, with car tires representing one of the most significant sources. In the United States alone, an estimated 1,524,740 metric tons of tire wear particles (TWP) are released into the environment annually, primarily through road friction. This study aims to evaluate the impacts of TWP exposure on larval growth, particle internalization, and behavior in two model species: the estuarine fish Menidia beryllina and the mysid shrimp Americamysis bahia. We used a cryo-milled tire tread (CMTT) composite provided by the U.S. Tire Manufacturers Association. The composite was a representative mixture of what may be in our environment and contained three types of tire in proportions that are estimated for the U.S. - 41% Passenger Car Tire, 14% Light Truck Tire, and 45% Truck/Bus Tire. To better simulate environmental conditions, micro- and nano-tire particles in our study were weathered using a solar simulator for 72 hours. Particularly, 5-day post-fertilization fish embryos and 7-day-old mysid shrimp were exposed to micro (1–20 μm) and nano (<1 μm) tire particles at four concentrations (10, 100, 1000, and 10,000 particles/mL), as well as to leachate derived from both pristine and weathered tire particles. At the conclusion of the experiment, behavioral assays were performed using a DanioVision Observation Chamber, where each organism was subjected to a dark: light cycle stimuli. Growth measurements were assessed through the index W/L× d (W = width, L = standard length, d = days the organisms were exposed to tire particles), and organisms were cleared with clearing reagents (Cubic-L and Cubic-R solutions) to visualize and count the internalized particles. Previous studies have shown that tire particles from a single tire type can induce behavioral toxicity and inhibit growth in these species. This research advances our understanding by evaluating, for the first time, the effects of both pristine and weathered environmentally relevant multi-tire mixtures on M. beryllina and A. bahia.