Car and truck tire wear particles in complex environmental samples - A quantitative comparison with traditional microplastic polymer mass loads

Tire wear particles (TWP) are assumed to be the most dominant source of environmental microplastics (MP). Besides rubber components around 60% of tires are additives such as filling material and various chemicals added for vulcanization. The inevitably released TWP in daily traffic are therefore considered a threat to the ecosystem. Nevertheless, published studies on MP mass loads often exclude elastomers. Data concerning composition and concentrations of TWP compared to prominent traditional MP polymers, such as polyethylene, polypropylene, poly(ethylene terephthalate) and poly(vinyl chloride), are missing. Identification and quantification of TWP was implemented in an existing pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) method for MP determination. An approach to differentiate between car and truck tire wear and to quantify their respective mass loads is presented. Complex environmental samples such as road dust, fresh water and marine sediments, blue mussels, and marine salts were partly retrospectively analyzed using Py-GC/MS. The results showed ratios of car to truck tire wear up to 16 to 1 and underline the dominance of car compared to truck tire wear mass loads in all analyzed samples. Even though some retrospective data sets might be affected by suboptimal density separation conditions (NaBr, rho = 1.5 g/cm(3)), TWP concentrations in road dust clearly exceeded those of traditional MP (empty set 5 g TWP vs 0.3 g MP per kg road dust (dry weight). Samples included in this study, which were archived further away fromTWP sources such as roads, reflected decreasing TWP concentrations (empty set 24 mu g TWP vs. 107 mu g MP per kg sediment (dry weight); empty set 126 mu g TWP vs. 378 mu g MP per kg marine salt) or were no longer present (blue mussels), while traditional polymers were still ubiquitously distributed. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Tire wear particles are identified as a major source of environmental microplastics, posing a threat to the ecosystem. Results show that car tire wear dominates over truck tire wear in terms of mass loads, with significantly higher concentrations of tire wear particles compared to traditional microplastics.