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.

Polychlorinated biphenyls (PCBs) are toxic pollutants that are distributed worldwide. Indigenous microorganisms are believed to contribute significantly to their degradation. To better understand how environmental microorganisms degrade toxic pollutants, such as PCBs, we identified the indigenous bacteria involved in the natural attenuation of PCBs and PCB congener profiles in sediments from harbors on Awaji Island, Hyogo, Japan. High-resolution gas chromatography and high-resolution mass spectrometry (HRGC/HRMS) were used to analyze the PCB congener profiles. The sediment samples contained 2,200–3,800 pg PCBs/g dry, while the sediment sample with 100 pg PCBs/g dry served as a control harbor. The profiles of PCB congener composition in each homolog group using cosine theta (cos θ) analysis suggested that the polluted harbor with 2,200–3,800 pg PCBs/g dry was primarily affected by multiple commercial PCB products. Furthermore, the main congeners in the polluted harbor exhibited a positional preference that was not observed in the control harbor or in commercial PCB products; this suggests the possibility of microbial degradation rather than merely the presence of multiple commercial PCB products. Additionally, 16S ribosomal RNA (rRNA) next-generation sequencing (NGS) analysis revealed similar alpha-diversity but different bacterial community compositions between the two harbors, particularly in the sediments, with the presence of PCB-dechlorinating Dehalococcoidaceae species in the polluted harbor sediments. Polymerase chain reaction (PCR) amplification revealed the presence of PCB-dechlorinating bacteria, namely Dehalogenimonas sp., only in the polluted harbor. These findings suggest that anaerobic PCB-dechlorinating bacteria such as Dehalogenimonas sp. play a key role in the natural attenuation of PCBs by dechlorination in polluted harbors. Overall, we not only provided insight into the biodegradation process by indigenous microorganisms and the potential for the natural attenuation of PCBs in polluted environments but also demonstrated that the combination of PCB congener analysis using HRGC/HRMS and microbial analysis using environmental DNA is a powerful tool for assessing PCB pollution and indicating natural attenuation in the environment.

Since 1993, neonicotinoid insecticides have been used extensively in Japan, primarily for rice cultivation and pine forest protection. The spread of neonicotinoids to the natural environment is largely through runoff from agricultural lands; however, precipitation could also become a potential medium even though neonicotinoids have low vapor pressures. While previous studies have reported the dry deposition and particulates of neonicotinoids in the air, this study investigated the wet deposition of these insecticides. Rainwater samples from Tsukuba and Kashiwa, Japan, were collected and analyzed by liquid chromatography–tandem mass spectrometry in April, June, and September 2023, as well as in January, April, June, August, and September 2024. Results revealed that 91% of the samples contained neonicotinoids, with the highest total concentration of 1.72 ng/L detected in August 2024. Acetamiprid ranked first with a detection frequency of 82% and an average concentration of 0.36 ng/L, followed by thiacloprid (73%, 0.28 ng/L) and dinotefuran (45%, 0.52 ng/L). This research is the first report on neonicotinoid presence in precipitation, suggesting that neonicotinoids, as low volatile matter, can still be dispersed to the environment via precipitation.

Mercury is used in artisanal and small-scale gold mining (ASGM) to extract gold by forming an amalgam. This raises considerable concern about mercury pollution in the surrounding environment and plants. This study aimed to investigate mercury concentrations in soil and cacao in the ASGM area of Ghana and to evaluate the human health risk of mercury in cacao. Agricultural soil and cacao (root, leaf, bean, and pod) samples were collected from three ASGM communities (Manso Abore, Nweneso No. 1, and Nweneso No. 2) in the Ashanti Region of Ghana. The mean total mercury concentrations in the soil were 76±36 µg/kg dry weight (n=42), corresponding to moderate contamination by the contamination factor. In the cacao samples, the highest mean total mercury concentration was found in the roots (211 µg/kg dry weight, n=12) and lowest in the beans (27 µg/kg dry weight, n=12). The bioaccumulation and transfer factors indicated a high accumulation of mercury in the roots of cacao (bioaccumulation factor=3.1) from the soil but a lesser accumulation in the aerial parts from the roots (transfer factor<1). The health risk assessment from the ingestion of cacao beans indicated no possibility of noncarcinogenic health effects (hazard quotient<1). Continuous mercury pollution may lead to accumulation along the food chain, which may be detrimental to human health. Therefore, strict measures and monitoring in ASGM communities are needed to protect human health.

Microplastics are ubiquitous environmental contaminants that have significant adverse effects on ecosystems and human health. Lichens, recognized as reliable pollution bioindicators, have been proposed as effective monitors of atmospheric microplastic contamination. This study investigated the dynamics of microplastic deposition and accumulation in lichen thalli using Ramalina celastri as a model organism. Lichen thalli were exposed to controlled suspensions of microfibers across three size categories (<1, 1, and 5 mm) over a 4-week period. Microplastic particles were extracted using a novel sodium hypochlorite oxidation technique. The results revealed a distinct differentiation between the deposited microfibers, which correlated with the environmental deposition rates, and the accumulated microfibers, which showed temporal increases and greater retention of smaller particles. These findings challenge the existing assumptions in microplastic research that extracted particles solely represent accumulated material, emphasizing the need for refined terminology. To address this, we propose the term “retained” to encompass deposited and accumulated particles. The sodium hypochlorite oxidation technique provides a cost-effective and safer alternative to traditional wet peroxide oxidation, enhancing its feasibility for researchers in resource-limited settings. Furthermore, the use of NaCl and oil extraction proved effective in isolating microplastics across varying densities. This work underscores the importance of precise definitions and robust methodologies in the study of microplastic bioindicators, contributing to a more comprehensive understanding of microplastic dynamics in lichens and their utility in environmental monitoring.

The chromatographic separation of tetra- to octa-chlorinated dibenzo-p-dioxins and dibenzofurans was evaluated using a DB-17ms column 80 m long, with a 0.18-mm inner diameter (ID) and a 0.18-μm film thickness. This column effectively resolved two 2,3,7,8-substituted congeners, 1,2,3,7,8-pentachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran, which had previously been co-eluted with other congeners on a 60-m×0.25-mm ID, 0.25-μm-film-thickness DB-17ms column. All seventeen 2,3,7,8-substituted congeners were separated effectively in a single injection using the narrow-bore extended-length DB-17ms column. To the best of our knowledge, this represents the first report of a column capable of achieving effective separation of all seventeen 2,3,7,8-substituted congeners.

A total of 27 groundwater samples, including deep-well (>100 m) samples; 8 surface water samples, including Nile River samples; 9 wastewater samples; and 2 tap-water samples were collected in Sudan and analyzed for artificial sweeteners and antibiotics. Acesulfame (ACE), an artificial sweetener, was frequently (59%) detected in groundwater samples collected in Khartoum, the highly populated capital city of Sudan, with a concentration ranging from 2 ng/L to 2,900 ng/L, and in sewage samples (~10,000 ng/L). ACE concentrations detected in the groundwater were positively correlated with the population density. No substantial amounts of ACE were detected in the Nile River at Khartoum, although high ACE levels were expected because of the large population and insufficiency of the sewage treatment system. These findings suggest that sewage generated in Khartoum is trapped in the ground rather than discharged to the Nile River, probably because the arid climate limits runoff and facilitates sewage infiltration into the ground. This contrasts with the findings reported in tropical Asian rivers. In addition, we detected ACE in deep groundwater in other arid countries, including Iran, Kenya, and Mozambique, where the available aquifers are primarily unconfined and vulnerable to the vertical infiltration of pollutants from the ground. These findings suggest that populated cities in the arid climate zone are at a high risk of deep groundwater contamination with sewage and associated chemicals. Antibiotics were widely detected in urban and rural environments. In the Nile River and the deep groundwater at Khartoum, tetracyclines, especially chlortetracycline (CTC), predominated among the 17 antibiotics measured, including sulfonamides, macrolides, and tetracyclines. CTC was detected in 65% of the samples, with a concentration range of 0.3–90 ng/L. The concentrations of sewage-derived antibiotics estimated from the ACE concentrations and the CTC to ACE ratios in sewage were much lower than those observed in the Nile River and its vicinities. Considering the usage pattern of antibiotics in Sudan, we concluded that the antibiotics were derived from veterinary use. This study demonstrated that artificial sweeteners and antibiotics combined are useful as molecular markers for investigating environmental water pollution in developing countries with highly arid climates.

Hexavalent chromium (Cr(VI)) is a hazardous substance but has been used in various industrial applications. Consequently, it has caused severe environmental pollution in many regions worldwide. One notable site of concern is the final landfill of a former chemical factory located approximately 8 km east of central Tokyo, where high concentrations of Cr(VI) leach into the public sewage system and the surrounding environment. Rainfall plays an important role in the transport of substances in the environment; however, its specific effects on Cr(VI) behavior within this area remain unclear. To elucidate the effect of rainfall on the outflow of Cr(VI) from the former chemical factory site, we examined the relationship between Cr(VI) concentration, pH, redox potential (Eh), and antecedent dry hours in stagnant water samples collected from a rainwater inlet, after classifying the data based on the presence or absence of rainfall within a defined preceding time frame. The results revealed a strong positive correlation between Cr(VI) concentration and pH in samples collected after rainfall, thereby proving that rainfall accelerates Cr(VI) outflow. This phenomenon likely occurs because the hexavalent chromium slag, a potential source of contamination, is a highly alkaline material. Additionally, the rainfall-induced Cr(VI) outflow peaked approximately 6–24 hours following the rainfall event. This finding was supported by the relationships among the 4 factors mentioned above. The combination of low Eh values and high Cr(VI) concentrations in the water samples appears to result from a decline in Eh and accumulation of Cr(VI) in the groundwater during antecedent dry periods. This study highlights the importance of reinforcing pollution control measures, particularly during the critical 24 h window following rainfall. Further quantitative studies are needed to develop effective countermeasures to better understand Cr(VI) behavior, considering hourly rainfall patterns.

Pyrolysis-gas chromatography-mass spectrometry is one of the most promising techniques for investigating plastic particles ranging from micro to nano-sizes (less than 1 µm). However, most studies on the occurrence of micro- and nanoplastics in the air applied single-shot analysis (only pyrolysis), whereas double-shot analysis (thermal desorption followed by pyrolysis) has not been fully investigated. This paper compares single-shot and double-shot methods to investigate the pyrolysis conditions for the detection and quantification of urban outdoor airborne plastics. The findings are applied to the outdoor air in Tokyo (Japan), Bangkok (Thailand), and Kathmandu (Nepal). Relative to single-shot, the double-shot analysis detected the indicator substances of polymethylmethacrylate, polyamide 66, and polypropylene in the aerosol collected in Kyoto city, Japan, and separated some volatile compounds, such as those produced by the pyrolysis of the polymer. In addition, the result indicates that the double-shot analysis may affect the quantification of polyethylene terephthalate (PET) because the pyrolysis of this polymer can be initiated at a thermal desorption temperature of 320°C. Therefore, we optimized the double-shot method to a maximum final temperature of 300°C for thermal desorption and achieved good PET quantification. The total airborne plastic concentration sized between 0.43 and 11 µm was 325 ng/m³ in Tokyo, 141 ng/m³ in Bangkok, and 434 ng/m³ in Kathmandu. The size distribution of each polymer varied; for polyethylene and PET, the concentrations of the nano-sized fractions tended to be similar or higher than those of the micro-sized fractions, whereas styrene-butadiene rubber was not detected at the size fractions under 3.3 µm in Tokyo and 2.1 µm in Bangkok and Kathmandu.

The concentrations of 12 metals (V, Co, Ni, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, and Pb) in 150 duplicate diet samples collected from the adult Japanese during 2017–2019 were measured using inductively coupled plasma mass spectrometry preceded by nitric acid digestion. The concentrations of Ag, Sb, and Pb were below the detection limit in some samples, partly because of the low abundance in the diet and analytical contamination. The daily intake of the metals was calculated by multiplying the concentration in the diet by the consumption weight of the diet. The median daily intake was 7.20, 7.09, 86.4, 1.49×10³, 1.21×10³, 169, <0.71, 12.0, 0.712, 5.57, 334, and 2.24 μg/person/day for V, Co, Ni, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, and Pb, respectively. Oral exposure via the diet was nearly 100% of the total oral intake (diet+soil+house dust), except for V, Sb, and Pb, to which soil and/or house dust was estimated to contribute 20%–34% of the total intake. The intake levels of all of the metals were below the US EPA Reference Dose (RfD) (except for Co, Rb, Cs, and Pb for which RfD is not available), indicating that the health risk due to dietary intake, as well as oral intake, would be minimal. As diet is the predominant oral exposure source of metals, periodic and systematic monitoring of daily diet levels is warranted in Japan.

Plastic debris in coastal environments can serve not only as a physical pollutant but also as a carrier of trace elements. In this study, we analyzed 34 elements in four coastal invertebrate species—Nerita polita (Mollusca: Gastropoda), Cellana testudinaria (Mollusca: Gastropoda), Atactodea striata (Mollusca: Bivalvia), and Coenobita purpureus (Crustaeca: Decapoda: Anomura)—collected from two stations (Nita Beach and Furuzamami Beach) on Zamami-jima Island in the Ryukyu Islands. We assessed the uptake and accumulation of plastic-derived trace elements and interspecific differences. Trace element concentrations in muscle and internal organ tissues were measured using inductively coupled plasma mass spectrometry, and comparisons were made between stations, years, and species. The results revealed that concentrations of plastic additive-derived elements, such as As, Cd, Pb, and Cr, were higher at Nita Beach, where more plastic debris was observed, indicating plastic-derived contamination. In particular, As was detected at high concentrations across multiple tissues and species, suggesting ongoing exposure. A temporal comparison using C. purpureus between 2018 and 2023 revealed a decreasing trend for highly toxic elements such as Cd and Pb, whereas As showed a slight increase, raising concerns about persistent contamination. Interspecific comparisons showed that trace element concentrations were higher in gastropods than in bivalves, likely owing to differences in digestive physiology, such as the absence of microplastic egestion mechanisms like pseudofeces. These results indicate that monitoring of plastic-derived trace element contamination requires sampling across multiple species, years, and seasons. Furthermore, the phenomenon of minimal differences between stations suggests that even sites with seemingly little debris may experience unexpected exposures, possibly because of factors such as temporary heavy-pollution events followed by cleanups or accumulation of debris in coastal forests.