Marine plastic debris (MPD) pollution is ubiquitous in Asian coastal areas; however, there is limited information on the types of polymers and quantification of MPD in the coastal regions of Myanmar. This study collected beach plastic debris samples from low- and high-tide strandlines across three coastal areas in the Ayeyarwady region to quantify and characterize the abundance of macroplastics (>25 mm) and mesoplastics (5–25 mm). The mean abundance values of plastic debris in the low-tide strandline were consistent: 1.7±0.5 pieces/m² in Ngayoke Kaung, 1.6±0.6 pieces/m² in Chaung Thar, and 1.1±0.7 pieces/m² in Ngwe Saung. In contrast, higher abundances of plastic debris were detected in the high-tide strandline, with 9.3±5.7 pieces/m² in Ngwe Saung, 7.0±4.4 pieces/m² in Chaung Thar, and 4.9±0.5 pieces/m² in Ngayoke Kaung. This variation may be attributed to the larger size of the MPD and its entanglement with the large driftwood. The dominant shapes of the MPD found in low- and high-tide strandlines were fragments, films, and foam, typically white or transparent. The types of polymers were analyzed using Fourier-transform infrared, revealing that polypropylene (PP) and polyethylene (PE) were the most abundant in all sampling sites. The primary sources of this plastic debris are likely consumer products such as food and drink packaging and aquaculture gear. The presence of plastic debris in Myanmar’s coastal areas may be linked to waste management practices, highlighting the need for enhanced environmental education within local communities to control plastic emissions into marine ecosystems.

Microplastics (MPs) and plastic additives have attracted global attention as emerging environmental pollutants. Herein, we analysed MPs and 56 organic plastic-derived chemicals in road dust (n=3), stormwater (n=4) and urban small-scale river sediment (n=8) samples collected from a downtown area of Kumamoto, Japan. The MP levels were 57,500–160,000 items/kg dw, 2.2–42 items/L and 1,600–15,800 items/kg dw in road dusts, stormwater and river sediments, respectively. The compositions of the polymers (tyre road wear particles [TRWPs], polymethyl methacrylate [PMMA] and polyethylene terephthalate [PET]) were consistent among the analysed samples; this result indicates that road dust–associated MPs were transferred to the river sediment via stormwater. A large amount of glass beads, an indicator of traffic-related particulate contaminants, was found in the road dust and sediments, suggesting that the urban small-scale river was strongly impacted by traffic activities. In total, 32 plastic-derived chemicals were identified in road dust and sediments with 6,900–32,000 and 620–13,000 ng/g dw concentrations, respectively. Notably, these concentrations were positively correlated with the abundance of MPs, indicating that MPs act as carriers of plastic-derived chemicals. We determined the concentrations of plastic additives in 28 traffic-related plastic products to identify the potential source of additive-derived chemicals in the road surface environment. Several road marking sheets and road paints contained large quantities (up to 1.7% w/w) of high-concerned substances, including phthalate esters, benzotriazole ultra-violet (UV) stabilisers and benzophenones. The additive profiles of the MPs and traffic-related products were similar to those of some PMMA-based MPs detected in the samples and PMMA-based road paints. This indicates that PMMA-based road paint was identified as an original source of MPs, contributing to 24%–54% of the total number of MPs in the road dust, stormwater and river sediment. In conclusion, an urban small-scale river was highly contaminated with road dust–associated MPs and plastic additives, and high-priority plastic products were identified as an important source of those contaminants in urban road areas.

This study analyzed benzotriazole UV stabilizers (BUVSs), including UVP, UVPS, UV329, UV9, UV320, UV350, UV326, UV327, UV328, and UV234, in beached polypropylene (PP) pellets. First, the efficiency of soaking extraction in hexane was confirmed. This extraction method was then applied to 37 PP pellet samples (each sample basically consisted of 50 pellets) collected from beaches worldwide (Europe, Africa, the Middle East, Asia, Oceania, and the Americas). Twenty samples had low levels of BUVSs that were <0.2 μg/g, while 14 samples exhibited high concentrations, ranging from >1 μg/g of BUVSs (sum of the 10 BUVSs) to 70 μg/g. These high concentrations were observed only for one or two BUVS (UV326, UV327, UV329, and UV328) in individual PP pellet samples. Piece-by-piece analyses of pellets from eight locations revealed sporadic and inhomogeneous occurrences of specific BUVSs. Pellets with high concentrations of BUVSs were industrially compounded with additives and/or were recycled, and they were even found on remote islands, such as, Macquarie Island, Hawaii Island, Ogasawara Island, and Hachijo Island. The concentrations of BUVSs in pellets from remote areas were similar orders of magnitude to those observed in anthropogenically impacted areas near industrial areas, such as Sydney or Tokyo. This study demonstrates that BUVSs, as plastic additives, travel in millimeter-sized plastics across thousands of kilometers without drastic desorption or degradation. The findings highlight the need for international regulation of plastics and associated chemicals.

Understanding realistic exposure profiles of mixtures is crucial for effectively predicting the ecological risks and effects of metal mixtures in natural environments on a large scale (e.g., at a country level). In this study, we aimed to compile available measurement data for metals relevant to ecological risk assessment in rivers across Japan, identify metals of particular concern based on their relative ecological risks, and derive realistic exposure profiles of these metals based on the compiled data. We focused on six metals of concern (Ni, Cu, Zn, Pb, Cd, and Al) selected by comparing available measurement data and 10% inhibition concentrations for the daphnid Ceriodaphnia dubia. We then compiled measurement data on these metal concentrations, ensuring sufficiently low detection/quantification limits relevant to ecological risk assessments, from a total of 531 riverine sites. At 194 metal-contaminated sites, concentrations generally increased in the following order: Cd (median: 0.013 μg/L), Pb (0.072 μg/L)<Ni (0.45 μg/L)<Cu (1.2 μg/L)<Zn (9.1 μg/L), Al (22 μg/L). Using hierarchical cluster analysis, we classified the metal-contaminated sites into three groups (Group 1: 56 sites; Group 2: 104 sites; and Group 3: 34 sites). Groups 1 and 3 were characterized by higher concentrations of Cd and Ni, respectively, compared to Group 2. Further compilation and accumulation of measurement data, particularly in small rivers (e.g., tributaries of major rivers), are required to more accurately assess contamination levels and ecological risks from metals in rivers nationwide.

It is fundamental to understand the status of microplastic contamination in various sea turtle rookeries to assess the current and future effects of microplastics on sea turtles. The Ogasawara Islands, Tokyo, Japan, are the largest rookeries for green turtles (Chelonia mydas) in the Northwest Pacific and are remotely located 1,000 km from the Japanese mainland. To assess whether microplastic contamination occurred in the important nesting beaches of green turtles in the Northwest Pacific, we investigated the abundance and polymer types of microplastics collected at the surface and the nest depth (60 cm deep) in the sand of the 14 nesting beaches of the Ogasawara Islands. Results showed that microplastics were found at both the surface and the nest depth, and no significant difference in microplastic abundance was observed between them. The presence of microplastics at nest depth may be due to oceanographic and turtle nesting processes. Polystyrene, polypropylene, and polyethylene were identified, and expanded polystyrene was predominant. Furthermore, hexabromocyclododecanes, which are frequently compounded additives for expanded polystyrene, were semi-quantitatively analyzed using a pyrolizer coupled with a gas chromatograph-mass spectrometer in half of the expanded polystyrene microplastics collected in the present study. Result showed that hexabromocyclododecanes were detected in more than 30% of the analyzed microplastics, and the microplastics from both the surface and the nest depth contained hexabromocyclododecanes. The toxicological effect of such plastic-associated chemicals on turtles is a concern if they are transferable during egg incubation. Our data provide a baseline for assessing microplastic contamination in sea turtles on the Ogasawara Islands.