Identification and quantification of additive-derived chemicals in beached micro-mesoplastics and macroplastics

Quantification of additives in beached plastic debris from Aotearoa New Zealand

Plastics have become an essential part of modern society. Their properties can be easily manipulated by incorporating additives to impart desirable attributes, such as colour, flexibility, or stability. However, many additives are classified as hazardous substances. To better understand the risk of plastic pollution within marine ecosystems, the type and concentration of additives in plastic debris needs to be established. We report the quantification of thirty-one common plastic additives (including plasticisers, antioxidants, and UV stabilisers) in beached plastic debris collected across Aotearoa New Zealand. Additives were isolated from the plastic debris by solvent extraction and quantified using high-resolution liquid chromatography-mass spectrometry. Twenty-five of the target additives were detected across 200 items of debris, with plasticisers detected at the highest frequency (99 % detection frequency). Additives were detected in all samples, with a median of four additives per debris item. A significantly higher number of additives were detected per debris item for polyvinyl chloride (median = 7) than polyethylene or polypropylene (median = 4). The additives bis(2-ethylhexyl) phthalate, diisononyl phthalate, diisodecyl phthalate, and antioxidant 702 were detected at the highest concentrations (up to 196,930 μg/g). The sum concentration of additives per debris item (up to 320,325 μg/g) was significantly higher in polyvinyl chloride plastics (median 94,716 μg/g) compared to other plastic types, primarily due to the presence of phthalate plasticisers. Non-target analysis was consistent with the targeted analysis, indicating a higher number and concentration of additives in polyvinyl chloride debris items compared to all other polymer types. Feature identification indicated the presence of more additives than previously detected in the targeted analysis, including plasticisers (phthalate and non-phthalate), processing aids, and nucleating agents. This study highlights phthalates and polyvinyl chloride as key targets for consideration in ecotoxicology and risk assessments, and the development of policies to reduce the impacts of plastic pollution.

Solvent extraction of UV stabilizers in plastics: A step towards methodology harmonization

The environmental pollution caused by plastics and their chemical additives has drawn global attention. UV stabilizers are among the major plastic additives that were used to protect against discoloration and degradation under sunlight. They are recognized as harmful due to its persistence, bioaccumulation, adverse effects, and potential for long-range environmental transport via plastics. However, non-harmonized methodology to analysis UV stabilizers in plastics has brought remarkable challenge to compile data across studies and conduct further risk assessment. Especially, the extraction solvent was diverse, whereas their extract efficiency was unknown. To address this knowledge gap, this study assessed the extraction efficiency of three commonly used organic solvents (dichloromethane (DCM), methanol (MeOH) and toluene (PhMe)) for UV stabilizers in different type of plastics, including foil-based polymer (Polyethylene, Polypropylene, Polystyrene, and Polyethylene terephthalate), bio-based plastics (Polylactic acid) and tire rubber. A total of 8 UV stabilizers were detected with a concentration range between 0.01 and 257.94 μg/g. OC had the highest detection rate (100%) and concentration (0.21-257.94 μg/g). The extraction performance of the three extractants was further evaluated, and it was found that not only the extraction performance but also the stability, DCM performed significantly better than MeOH and PhMe.

Leaching potentials of microplastic fibers and UV stabilizers from coastal-littered face masks

Synthetic fibrous textiles are ubiquitous plastic commodities in everyday existence. Nevertheless, there exists a dearth of understanding regarding their environmental occurrence and the releasing capacities of associated additives. In this study, ten additives were determined in twenty-eight kinds of daily used plastic products including face masks, synthetic clothing, and food containers. Our results revealed that a typical kind of fibrous plastic, face masks, contained a greater variety of additives with UV stabilizers in particular, when compared to other plastic commodities. The above phenomena triggered our field investigation for the occurrence and release potentials of face mask fibers and the co-existing UV stabilizers into the environment. We further collected 114 disposed masks from coastal areas and analyzed their UV stabilizer concentrations. Results showed that the abundance of littered face masks ranged from 40-1846 items/km2 along the Yangtze Estuary, China; and UV stabilizers were of 0.3 ± 0.7 ng/g and 0.7 ± 1.7 ng/g in main bodies and ear ropes, respectively. The UV stabilizer concentrations in the field collected masks were only ∼7 % of their new counterparts, implying their potential leaching after disposal. By simulating the weathering scenario, we predict that a substantial amount of microplastics, with 1.1 × 1010 polypropylene fibers and 3.7 × 1010 polyester fibers, are probably be released daily into the coastal environment after face masks disposal; whereas the accompanied leaching amount of UV stabilizers was relatively modest under the current scenario.

Detection of benzotriazole-type ultraviolet stabilizers in sea turtles breeding in the Northwest Pacific Ocean

Benzotriazole-type ultraviolet stabilizers (BUVSs) are emerging contaminants whose exposure to wildlife is of concern. In this study, we investigated the contamination status of BUVSs in green turtles (Chelonia mydas) breeding at Ogasawara Islands, Japan, through chemical analysis of 10 BUVSs and 26 congeners of polychlorinated biphenyls (PCBs) in adipose tissue (n = 21) and blood plasma (n = 9). BUVSs were detected significant levels in adipose tissue (19 of 21 turtles), and UV-327 (not detected - 14.8 ng/g-lipid, detection frequency: 76 %), UV-326 (not detected - 24.1 ng/g-lipid, 29 %), and UV-328 (not detected - 5.8 ng/g-lipid, 24 %) were frequently detected. Turtles exhibiting sporadically high concentrations of BUVSs (>10 ng/g-lipid) did not necessarily correspond to individuals with high total PCB concentrations (1.03-70.2 ng/g-lipid). The sporadic occurrence pattern of BUVSs suggested that these contaminants in sea turtles cannot be explained solely by diet but are likely derived from plastic debris.

Source traceability of microplastics in road dust using organic/inorganic plastic additives as chemical indicators

Microplastics (MPs) are environmental pollutants of great concern around the world. The source of MPs in road dust need to be identified to develop strategies to control and reduce MPs emissions by stormwater runoff, one of the main sources of MPs to the aquatic environment. However, little information on the sources of MPs in road dust is available due to lack of their suitable indicators. In this study organic/inorganic plastic additives were used as chemical indicators to understand the source of MPs in road dust. The polymers, organic additives, and heavy metals in 142 commercial plastic products suspected of being source of MPs in road dust were determined. As the results, 147 organic additives and 17 heavy metals were identified, and different additive profiles were found for different polymer types and use application of plastic products. Further, 17 road dust samples were collected from an urban area in Kumamoto City, Japan. and analyzed the MPs (1-5 mm diameter) and their additive chemicals. Polymethyl methacrylate (PMMA) was the dominant polymer accounting for 86 % in the samples, followed by ethylene vinyl acetate (EVA) and polyvinyl chloride (PVC). In total, 48 organic additives and 14 heavy metals were identified in the MPs samples. The organic/inorganic additive profiles of plastic products and MPs in road dust were compared, and several road dust-associated MPs had similar additive profiles to road paints, braille blocks, road marking sheets, and reflectors. This suggested that the MPs were originated from these plastics on the road surface. Road paint was the most important contributor of MPs in road dust (60 % of the MPs), followed by braille block (23 %), road marking sheet (8.3 %), and reflector (2.4 %). These results indicated that organic/inorganic plastic additives in plastic products can be used as chemical indicators to trace the sources of MPs in road dust.

A global review on the abundance and threats of microplastics in soils to terrestrial ecosystem and human health

Soil is the source and sink of microplastics (MPs), which is more polluted than water and air. In this paper, the pollution levels of MPs in the agriculture, roadside, urban and landfill soils were reviewed, and the influence of MPs on soil ecosystem, including soil properties, microorganisms, animals and plants, was discussed. According to the results of in vivo and in vitro experiments, the possible risks of MPs to soil ecosystem and human health were predicted. Finally, in light of the current status of MPs research, several prospects are provided for future research directions to better evaluate the ecological risk and human health risk of MPs. MPs concentrations in global agricultural soils, roadside soils, urban soils and landfill soils had a great variance in different studies and locations. The participation of MPs has an impact on all aspects of terrestrial ecosystems. For soil properties, pH value, bulk density, pore space and evapotranspiration can be changed by MPs. For microorganisms, MPs can alter the diversity and abundance of microbiome, and different MPs have different effects on bacteria and fungi differently. For plants, MPs may interfere with their biochemical and physiological conditions and produce a wide range of toxic effects, such as inhibiting plant growth, delaying or reducing seed germination, reducing biological and fruit yield, and interfering with photosynthesis. For soil animals, MPs can affect their mobility, growth rate and reproductive capacity. At present epidemiological evidences regarding MPs exposure and negative human health effects are unavailable, but in vitro and in vivo data suggest that they pose various threats to human health, including respiratory system, digestive system, urinary system, endocrine system, nervous system, and circulation system. In conclusion, the existence and danger of MPs cannot be ignored and requires a global effort.

Leaching and transformation of chemical additives from weathered plastic deployed in the marine environment

Plastic pollution causes detrimental environmental impacts, which are increasingly attributed to chemical additives. However, the behaviour of plastic additives in the marine environment is poorly understood. We used a marine deployment experiment to examine the impact of weathering on the extractables profile, analysed by liquid chromatography-mass spectrometry, of four plastics at two locations over nine months in Aotearoa/New Zealand. The concentration of additives in polyethylene and oxo-degradable polyethylene were strongly influenced by artificial weathering, with deployment location and time less influential. By comparison, polyamide 6 and polyethylene terephthalate were comparatively inert with minimal change in response to artificial weathering or deployment time. Non-target analysis revealed extensive differentiation between non-aged and aged polyethylene after deployment, concordant with the targeted analysis. These observations highlight the need to consider the impact of leaching and weathering on plastic composition when quantifying the potential impact and risk of plastic pollution within receiving environments.

The molecular level degradation state of drift plastics in the Sea of Japan coastline

Polyethylene (PE) and polyethylene terephthalate (PET) are among the most abundant plastics polluting the oceans. However, their environmental fate depends on how they have been weathered. Due to its unique geography, the Sea of Japan is a pollution hotspot where plastics accumulate. In this study, the structures of plastics, having drifted into the Sea of Japan coastline environment, were analyzed with a particular focus on examining polymer crystallization and carbonyl formation; two factors which influence microplastic formation and the adsorption of contaminants onto plastic surfaces. PE in the coastal environment did not show evidence of crystallization, although carbonyl formation did increase. By contrast, PET bottles were shown to not be uniform in structure, with unaged bottles being less crystalline in the neck component compared to the body. Because of this difference, in environmental PET bottles, it was the bottle neck that showed increases in crystallization and carbonyl group formation.

Impact of accelerated weathering on the leaching kinetics of stabiliser additives from microplastics

The release of additives from microplastics is known to harm organisms. In the environment, microplastics are exposed to weathering processes which are suspected to influence additive leaching kinetics, the extent and mechanism of which remain poorly understood. We examined the impact of weathering on stabiliser additive leaching kinetics using environmentally relevant accelerated weathering and leaching procedures. Nine binary polymer-additive formulations were specifically prepared, weathered, analysed, and evaluated for their leaching characteristics. Cumulative additive release (Ce) varied widely between formulations, ranging from 0.009 to 1162 µg/g. Values of Ce generally increased by polymer type in the order polyethylene terephthalate < polyamide 6 < polyethylene. The change in leaching kinetics after accelerated weathering was incongruous across the nine formulations, with a significant change in Ce only observed for three out of nine formulations. Physicochemical characterisation of the microplastics demonstrated that additive blooming was the primary mechanism influencing the leaching response to weathering. These findings highlight the dependency of additive fate on the polymer type, additive chemistry, and the extent of weathering exposure. This has significant implications for risk assessment and mitigation, where the general assumption that polymer weathering increases additive leaching may be too simplistic.

Cross-sectional microstructural analysis to evaluate the crack growth pattern of weathered marine plastics

Fragmentation of degraded plastics and release of smaller secondary microplastics is usually attributed to the growth of environmental stress cracks. Analysis of crack patterns derived from chemical degradation can be useful not only for assessing the cause of plastic fracture and evaluating the useful lifetime of a product, but it can also potentially provide valuable information on the generation of microplastics. However, the literature with respect to microplastics generation is generally limited to surface observations of polypropylene and polyethylene. Here, we used ion-beam milling to prepare cross-sections of fragments of 15 plastic products made from five commodity plastics (polypropylene, polyethylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate) that were collected at two beaches in Japan, and then we examined the microstructures of those cross-sections by means of scanning electron microscopy and energy dispersive X-ray spectroscopy. Crack growth in the depth direction was examined to provide insights into microplastic generation behavior. In all of the polypropylene samples, and some of the low-density polyethylene and polystyrene samples, cracks with a depth exceeding 100 μm from the sample surface were observed. Considering that crack growth causes fracture of degraded plastic and microplastic release, these observations suggest the release of sharp-edged microplastics from the crack fracture surface. In contrast, in the high-density polyethylene and polyvinyl chloride samples, crack growth was limited to within 20 μm of the sample surface, suggesting the release of irregularly shaped microplastics and additive particles. The present results suggest that the degradation behavior of plastic products in the depth direction is dependent on the type of plastic.