STOTEN's minimum requirements for measurement of plastics in environmental samples

Adapting Methods for Isolation and Enumeration of Microplastics to Quantify Tire Road Wear Particles with Confirmation by Pyrolysis GC-MS

The complex, varied composition (i.e., rubbers/elastomers, carbon black, fillers, additives, and embedded road materials) and wide density range of tire road wear particles (TRWPs) present challenges for their isolation and identification from environmental matrices. Reliable quantification is important for understanding the environmental fate and potential adverse effects of TRWPs. To address environmental monitoring needs, the present work adapts a series of isolation and identification steps from methods commonly applied for microplastic analysis for single-particle-level enumeration of TRWPs from environmental samples. We present the method performance of a two-stage density separation with saturated NaCl and sodium polytungstate to isolate TRWPs from sediment matrices, the compatibility of tire microrubber with reagents used for digestion of environmental matrices, and the use of elasticity and heat resistance observations to differentiate TRWPs from bitumen particulates, which are potential visual interference. We found that alkaline digestions (NaOH and KOH) are compatible with tire microrubbers, but hydrogen peroxide and sodium hypochlorite can cause TRWPs to lose elasticity and flatten or break when probed. The adapted methods were applied to road dust samples, and a subset of identified TRWPs was qualitatively confirmed by both scanning electron microscopy and pyrolysis-gas chromatography-mass spectrometry. Further, a compilation of aspect ratio measurements of TRWPs between 63 and 500 μm (N = 780) that were isolated from urban sediments shows the potential diversity of TRWP shapes in the environment.

Microplastics monitoring in freshwater systems: A review of global efforts, knowledge gaps, and research priorities

The escalating production of synthetic plastics and inadequate waste management have led to pervasive microplastic (MP) contamination in aquatic ecosystems. MPs, typically defined as particles smaller than 5 mm, have become an emerging pollutant in freshwater environments. While significant concern about MPs has risen since 2014, research has predominantly concentrated on marine settings, there is an urgent need for a more in-depth critical review to systematically summarize the current global efforts, knowledge gaps, and research priorities for MP monitoring in freshwater systems. This review evaluates the current understanding of MP monitoring in freshwater environments by examining the distribution, characteristics, and sources of MPs, alongside the progression of analytical methods with quantitative evidence. Our findings suggest that MPs are widely distributed in global freshwater systems, with higher abundances found in areas with intense human economic activities, such as the United States, Europe, and China. MP abundance distributions vary across different water bodies (e.g., rivers, lakes, estuaries, and wetlands), with sampling methods and size range selections significantly influencing reported MP abundances. Despite great global efforts, there is still a lack of harmonized analyzing framework and understanding of MP pollution in specific regions and facilities. Future research should prioritize the development of standardized analysis protocols and open-source MP datasets to facilitate data comparison. Additionally, exploring the potential of state-of-the-art artificial intelligence for rapid, accurate, and large-scale modeling and characterization of MPs is crucial to inform effective strategies for managing MP pollution in freshwater ecosystems.

Understanding Human Health Impacts Following Microplastic Exposure Necessitates Standardized Protocols

Microplastics (MPs; 1 µm to 5 mm) are a persistent and pervasive environmental pollutant of emergent and increasing concern. Human exposure to MPs through food, water, and air has been documented and thus motivates the need for a better understanding of the biological implications of MP exposure. These impacts are dependent on the properties of MPs, including size, morphology, and chemistry, as well as the dose and route of exposure. This overview offers a perspective on the current methods used to assess the bioactivity of MPs. First, we discuss methods associated with MP bioactivity research with an emphasis on the variety of assays, exposure conditions, and reference MP particles that have been used. Next, we review the challenges presented by common instrumentation and laboratory materials, the lack of standardized reference materials, and the limited understanding of MP dosimetry. Finally, we propose solutions that can help increase the applicability and impact of future studies while reducing redundancy in the field. The excellent protocols published in this issue are intended to contribute toward standardizing the field so that the MP knowledge base grows from a reliable foundation. © 2024 Wiley Periodicals LLC.

Rebuttal of the arguments put forward in the Letter to the Editor by Nizzetto et al

In their Letter to the Editor, Nizzetto et al. challange a recent article in which I show that there has been unwarranted alarmism about biodegradable mulch films due to the publication of numerous articles based on preliminary data that are irrelevant for drawing conclusions on environmental risk. The tendency to over-emphasise results in order to attract attention is a growing problem in the scientific world and has been studied by many scholars. Nizzetto et al. accuse me of not using scientific methodology and of not disclosing that I am a scientist working for a company that produces biodegradable plastics. In this rebuttal I show that Nizzetto et al.'s accusations suffer from a number of logical fallacies, in particular the "straw man" fallacy and the "ad hominem" fallacy.

The characteristics and influencing factors of farmland soil microplastic in Hetao Irrigation District, China

Microplastic pollution, a major global concern, has garnered increasing attention in agricultural ecosystem research. China's Hetao Irrigation District, vital for grain production in the Yellow River Basin, lacks sufficient research on microplastic pollution of agricultural soils. This study, based on a detailed background investigation and testing of 47 samples, is the first to elucidate the characteristics and potential influencing factors of microplastics in the Hetao Irrigation District. The abundance of microplastics in the farmland soil ranged from 1810 to 86331 items/kg, with 90% measuring below 180 µm and mainly in film and fragment forms. Predominant polymers were polyethylene (PE, 43.0%) and polyamide (PA, 27.8%). Key pollution influencers were identified as agricultural inputs, with low-density polyethylene (LDPE) being the most extensively used plastic type. The carbonyl index and hydroxyl indices of the detected LDPE microplastics ranged from 0.041 to 0.96 and 0.092 to 1.20, respectively. The study highlights the significance of mulching management and agronomic practices in shaping microplastic characteristics. Potential pollution sources include agricultural inputs, irrigation equipment, domestic waste, and tire wear. Proposed effective strategies include responsible plastic use, robust waste management, and irrigation system upgrades, establishing a foundation for future ecological risk assessments and effective management approaches in the Hetao Irrigation District. ENVIRONMENTAL IMPLICATION: The harmful substances studied in this paper are microplastics, which are widely distributed in the environment and have potential ecological risks. This study is the first to investigate the characteristics of microplastics in farmland soil within the Hetao Irrigation Area, a region that is of critical importance to agricultural production in the Yellow River Basin of China. The study provides comprehensive insights into the factors influencing the characteristics of microplastics and speculates on their sources. These findings offer a novel perspective on the assessment of microplastic contamination in the area and provide valuable recommendations for prevention and control measures.