Quantification of tire wear particles in road dust based on synthetic/natural rubber ratio using pyrolysis-gas chromatography-mass spectrometry across diverse tire types.

Increase in road traffic leads to increased concentrations of tire-wear particles (TWPs), a prominent source of microplastics from vehicles, in road dust. These particles can re-enter the atmosphere or move into aquatic ecosystems via runoff, impacting the environment. Consequently, accurately assessing and managing TWP levels in road dust is crucial. However, the ISO method (ISO/TS 20593 and 21396) uses a constant ratio of styrene-butadiene rubber (SBR) to natural rubber (NR) for all tires, disregarding the variability in tire composition across different types and brands. Our study found substantial SBR content (15.7 %) in heavyweight truck tires, traditionally believed to be predominantly NR. We evaluated the SBR/NR content in 15 tire types and proposed a method to more accurately evaluate TWP concentrations in road dust from five different locations. Our findings suggest that the conventional ISO method may underestimate the concentrations of TWP due to its reliance on a static ratio of SBR/NR. This study underscores the necessity for a more flexible approach that can adapt to the variability in SBR and NR content across different tire types. By delineating the limitations inherent in current assessment methods, our research contributes to a more adaptable understanding of TWP concentrations in road dust. This advancement prompts the development of a revised methodology that more accurately reflects the diverse compositions of tire rubber in environmental samples.

Rapid generation of aged tire-wear particles using dry-, wet-, and cryo-milling for ecotoxicity testing.

Strict environmental laws have been enacted to regulate the emission of exhaust particulate matter (PM), which is one of the most hazardous pollutants that reduce air quality and pose a serious risk to the human health. In addition, non-exhaust PM, such as road wear, tire wear, and brake wear debris, is a significant source of airborne pollutants. Road dust less than 100 µm in size may include tire wear particles (TWPs), which are broken down into finer particles with sizes on the order of tens of micrometers because of weathering. TWPs can be transported to water bodies via runoff, potentially contaminating water systems and negatively affecting aquatic ecosystems. Therefore, ecotoxicity tests using reference TWPs are required to investigate the impact of TWPs on the human health and environment. In this study, aged TWPs were produced using dry-, wet-, and cryo-milling methods, and the dispersion stability of TWPs in dechlorinated water was evaluated. Aged TWPs prepared by dry- and wet-milling had an average particle size of 20 µm, whereas pristine TWPs had an irregular shape and average particle size of 100 µm. The capacity of the ball-milling cylinder and excessively long 28-d generation time constrain the amount of aged TWPs that can be produced through conventional milling. In contrast, cryo-milling reduces the particle size of TWPs at the rate of -275.0 µm/d, which is nine times higher than that upon dry- and wet-milling. Dispersed cryo-milled TWPs had a hydrodiameter of 2.02 µm and were more stable in the aqueous phase in relation to the other aged TWPs. The results of this study suggest that cryo-milled TWPs can be used for aquatic exposure assessments as controls for real-world TWPs.

Rapid estimation of tire-wear particle concentration in road dust using PM10 and traffic data in a ternary plot.

Air pollution, a pressing global issue, is significantly exacerbated by airborne particulate matter (PM), affecting air quality and human health. Urban vehicular activities majorly contribute to PM rise through both exhaust and non-exhaust emissions. Despite strides in managing exhaust emissions, non-exhaust particles, such as tire wear particles (TWP) remain under-addressed. This research proposes a method for estimating TWP concentrations using PM10 data and traffic activity, which could offer a valuable tool for controlling roadside fine particles and TWP. This paper introduces a ternary plotting technique and step-by-step procedure to estimate TWP levels in road dust using only PM10 and traffic data. Traditional analysis of TWP via pyrolysis-gas chromatography-mass spectrometry is complex and time-consuming. Hence, our proposed approach presents an alternate method that leverages readily accessible PM and traffic data, providing critical information for road management interpretation. The triangular plot analysis demonstrated a linear correlation: [log(Traffic) + 2]-[250,000/TWP-13]-0.18PM10. While the resulting correlation may vary based on specific road conditions, the method can be tailored to different regions, offering insights into efficient estimation of TWP concentrations and promoting improved roadside pollution management.

Overall distribution of tire-wear particles, nano­carbon black, and heavy metals in size-fractionated road dust collected from steel industrial complexes.

Tire-wear particles (TWP) from vehicles serves as a non-exhaust emission source. The mass content of metallic species in road dust may increase owing to the traffic of heavy vehicles and industrial activity; consequently, metallic particles are also present in road dust. Herein, road dust collected from steel industrial complexes with high traffic of high-weight vehicles and the composition distribution of five size-fractioned particle sizes were analyzed. Road dust samples were collected from three areas near steelmaking complexes. The mass distribution of TWP, carbon black (CB), bituminous coal, and heavy metals (Fe, Zn, Mn, Pb, Ni, As, Cu, Cd, and Hg) in different size fractions of road dust was quantified by combining four different analytical techniques. In the magnetic separation for <45 µm fraction, 34.4 wt% and 50.9 wt% was removed for steelmaking and steel-related industrial complexes, respectively. As the particle size decreased, the mass content of Fe, Mn, and TWP increased. The enrichment factors of Mn, Zn, and Ni were higher than two, indicating that they were related to industrial activities in steel complexes. The maximum concentrations of TWP and CB originating from the vehicle varied depending on the region and particle size range: TWP 2.066 wt% at 45-75 µm (industrial complex) and CB 5.559 wt% at 75-160 µm (steel complex). Coal was only found in the steel complex. Finally, to reduce the exposure of the finest particles to road dust, three methods were suggested. Magnetic fraction must be removed from road dust using magnetic separation; the fly dust of coal during transportation must be suppressed, and covers must be used in coal yards; the mass contents of TWP and CB in road dust should be removed by vacuum cleaning instead of water flushing.