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Daphnia Reproductive Impacts Following Chronic Exposure to Micro- and Nano-Scale Particles from Three Types of Rubber

Brittany Cunningham , Bryan Harper, Susanne Brander, Stacey Harper

Abstract

Rationale High levels of rubber microplastics in aquatic environments are often attributed to particles from driven tires; however, the use of recycled or crumb rubber particles in outdoor surfaces is another source. Chronic toxicity assessments with tires are limited, and there is a need to evaluate impacts of rubber particles from different sources to better understand their role in conferring toxicity. Methodology We investigated the impact of chronic exposure of Daphnia magna to micro (1-20 µm, 3.13x10⁴ – 1.25x10⁵ particles/mL) and nano (<1 µm, 1.25x10⁵ – 1.00x10⁷ particles/mL) sized synthetic rubber particles. These included tire particles (TP) and two types of rubber from recycled tires (called recycled rubber (RR) and crumb rubber (CR)). Mortality, reproduction, and molting were assessed daily, and growth was measured at the end of the exposure. Additionally, the F₁ generation was reared to assess multigenerational impacts. Results Chronic exposure to micro rubber particles had severe impacts, delaying, decreasing, and even eliminating reproduction starting at 6.25x10⁵ particles/mL. Chronic exposure to nano rubber particles had less severe impacts, but delayed and decreased reproduction at the highest exposure level, 5.00x10⁷ particles/mL. Exposure to nano rubber in the parental generation had impacts on reproduction in the F₁ generation. Discussion This is the first comparison of chronic and generational toxicity between different sizes and compositions of rubber particles. The reproductive effects of chronic exposure to rubber particles could have devastating impacts on populations of Daphnia. Research is needed to identify which components leached from rubber particles impact reproductive ability.

EN23131  Accepted 11 November 2024

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