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2.
J Hazard Mater ; 427: 128144, 2022 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-34979390

RESUMO

Despite the importance of (micro)plastics in the release of plastic additives, the leaching mechanism of organic plastic additives from various plastic materials is poorly understood. In this study, the equilibrium leaching of five highly hydrophobic ultraviolet (UV) stabilizers (UV326, UV327, UV328, UV329, and UV531) from three plastics (low-density polyethylene (LDPE), polyethylene terephthalate (PET), and polystyrene (PS)), was investigated employing acetonitrile-water cosolvent systems. Their extrapolated water solubilities were in the 0.15-0.54 µg L-1 range, limiting their transport as "dissolved" in water and (micro)plastics are likely those particulate carriers. The equilibrium leaching of UV stabilizers from plastics was better explained by the Flory-Huggins model incorporating the nonideal behavior caused by the size disparity between UV stabilizers and polymer materials and their compatibility. Specifically, leaching of UV stabilizers from LDPE showed a positive deviation from Raoult's law, whereas slight negative deviations were observed in PET and PS. In addition, the equilibrium concentration of the benzotriazoles in LDPE increased linearly with the volume fraction up to only 0.4%. These observations could be explained by the unfavorable interactions of UV stabilizers with polyethylene, indicating that polymer type should be also important when evaluating the fate of hydrophobic additives. Because equilibrium distribution of additives between (micro)plastics and water is crucial for evaluating the fate and transport of hydrophobic plastic additives, further studies on the leaching equilibrium of various additives from different plastic materials are necessary.


Assuntos
Poluentes Químicos da Água , Plásticos , Polietileno , Polímeros , Poliestirenos , Poluentes Químicos da Água/análise
3.
Environ Sci Technol ; 54(3): 1503-1512, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31898898

RESUMO

Large quantities of microplastics are thought to be emitted to freshwater environments via wastewater treatment plants (WWTPs). To evaluate the occurrence of microplastics in Korean WWTPs, a nationwide study was conducted for the first time in 50 representative WWTPs with large treatment capacities. Grab sampling and laboratory filtration were used for influents, whereas in situ filtration using a custom-made sampling device was used for effluents. The filtrates were pretreated using wet peroxidation and density separation prior to the identification of microplastics with a dissection microscope and Fourier-transform infrared spectroscopy. Pooled analyses of the microplastics revealed that they were predominantly fragment-shaped, and thermoplastics and synthetic fibers were the dominant microplastic materials in WWTPs. The concentration ranged from 10 to 470 L-1 in influents and 0.004 to 0.51 L-1 in effluents. The removal efficiency of microplastics during wastewater treatment was calculated to be 98.7-99.99% in 31 WWTPs. Additionally, WWTPs using advanced phosphorus removal processes exhibited higher removal efficiency than those not implementing such processes. Power-law distribution was successful in describing microplastic particle sizes down to 100 µm, although it was not applicable for smaller particles. This comprehensive monitoring study provides information on the current level and characteristics of microplastics in WWTPs in Korea.


Assuntos
Águas Residuárias , Poluentes Químicos da Água , Monitoramento Ambiental , Microplásticos , Plásticos , República da Coreia , Inquéritos e Questionários , Eliminação de Resíduos Líquidos
4.
Chemosphere ; 222: 656-664, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30731386

RESUMO

Crude oil released into the environment contains many polycyclic aromatic hydrocarbons (PAHs). Alkylated PAHs are more abundant than unsubstituted PAHs and their toxicity is also of serious concern. Among the various physical, chemical, and biological weathering processes of crude oils, photodegradation is one of the most important for determining the environmental fate of oil residues. In this study, the photodegradation rate constants of naphthalene and alkylated naphthalenes were determined under simulated laboratory conditions at different temperature. Changes in the luminescence inhibition of Aliivibrio fischeri, as an indicator of the baseline toxicity, were observed in photodegradation mixtures. The major transformation products were also identified by gas chromatography-mass spectrometry. The photodegradation of naphthalene and the eight alkylated naphthalenes was described well by pseudo-first-order kinetics regardless of experimental temperature. The measured toxicity of the reaction mixtures obtained by photodegradative weathering slightly increased initially and then decreased with further weathering. In all cases, the observed toxicity was greater than accounted for by the parent compounds, indicating that the photodegradation products also contributed significantly to the overall toxicity of the mixtures. The identified photodegradation products were mostly oxygenated compounds such as alcohols, aldehydes, ketones, and quinones, which warrant further investigation.


Assuntos
Ecotoxicologia/métodos , Naftalenos/toxicidade , Fotólise , Aliivibrio fischeri , Alquilação , Cromatografia Gasosa-Espectrometria de Massas , Medições Luminescentes , Poluição por Petróleo/análise , Poluição por Petróleo/prevenção & controle , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Poluentes Químicos da Água/efeitos da radiação
5.
Environ Health Toxicol ; 33(3): e2018013-0, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30286589

RESUMO

Municipal sewage treatment plants (STPs) are thought to be important point sources of microplastics in freshwater systems and many peer-reviewed articles have been published on this issue since mid-2010s. In this review, we summarize existing literature on the occurrence of microplastics in STPs and experimental methods used for isolation and identification of microplastics. The number concentrations of microplastics in STP influents were 15.1-640 L-1 , whereas those in the STP effluents were highly variable and ranged from not detectable to 65 L-1 . For most of cases, conventional STPs are removing microplastics very effectively. Fragments and fibers are dominant shapes of microplastics. Thermoplastics (polyethylene and polypropylene) and polyester are the predominant materials recovered. Although further research is needed, size distribution of microplastics in STPs is likely to follow a power law, implying that different studies using different size cutoffs may be compared after establishing a power law relationship.

6.
Environ Sci Technol ; 50(21): 12004-12011, 2016 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-27715022

RESUMO

Worldwide, regulations of chemicals require short-term toxicity data for evaluating hazards and risks of the chemicals. Current data requirements on the registration of chemicals are primarily based on tonnage and do not yet consider properties of chemicals. For example, short-term ecotoxicity data are required for chemicals with production volume greater than 1 or 10 ton/y according to REACH, without considering chemical properties. Highly hydrophobic chemicals are characterized by low water solubility and slow bioconcentration kinetics, which may hamper the interpretation of short-term toxicity experiments. In this work, internal concentrations of highly hydrophobic chemicals were predicted for standard acute ecotoxicity tests at three trophic levels, algae, invertebrate, and fish. As demonstrated by comparison with maximum aqueous concentrations at water solubility, chemicals with an octanol-water partition coefficient (Kow) greater than 106 are not expected to reach sufficiently high internal concentrations for exerting effects within the test duration of acute tests with fish and invertebrates, even though they might be intrinsically toxic. This toxicity cutoff was explained by the slow uptake, i.e., by kinetics, not by thermodynamic limitations. Predictions were confirmed by data entries of the OECD's screening information data set (SIDS) (n = 746), apart from a few exceptions concerning mainly organometallic substances and those with inconsistency between water solubility and Kow. Taking error propagation and model assumptions into account, we thus propose a revision of data requirements for highly hydrophobic chemicals with log Kow > 7.4: Short-term toxicity tests can be limited to algae that generally have the highest uptake rate constants, whereas the primary focus of the assessment should be on persistence, bioaccumulation, and long-term effects.


Assuntos
Peixes , Invertebrados/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Interações Hidrofóbicas e Hidrofílicas , Cinética , Testes de Toxicidade
7.
Nutr Res Pract ; 10(5): 501-506, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27698957

RESUMO

BACKGROUND/OBJECTIVES: Corn silk (CS) extract contains large amounts of maysin, which is a major flavonoid in CS. However, studies regarding the effect of CS extract on cholesterol metabolism is limited. Therefore, the purpose of this study was to determine the effect of CS extract on cholesterol metabolism in C57BL/6J mouse fed high-fat diets. MATERIALS/METHODS: Normal-fat group fed 7% fat diet, high-fat (HF) group fed 25% fat diet, and high-fat with corn silk (HFCS) group were orally administered CS extract (100 mg/kg body weight) daily. Serum and hepatic levels of total lipids, triglycerides, and total cholesterol as well as serum free fatty acid, glucose, and insulin levels were determined. The mRNA expression levels of acyl-CoA: cholesterol acyltransferase (ACAT), cholesterol 7-alpha hydroxylase (CYP7A1), farnesoid X receptor (FXR), lecithin cholesterol acyltransferase (LCAT), low-density lipoprotein receptor, 3-hyroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase), adiponectin, leptin, and tumor necrosis factor α were determined. RESULTS: Oral administration of CS extract with HF improved serum glucose and insulin levels as well as attenuated HF-induced fatty liver. CS extracts significantly elevated mRNA expression levels of adipocytokines and reduced mRNA expression levels of HMG-CoA reductase, ACAT, and FXR. The mRNA expression levels of CYP7A1 and LCAT between the HF group and HFCS group were not statistically different. CONCLUSIONS: CS extract supplementation with a high-fat diet improves levels of adipocytokine secretion and glucose homeostasis. CS extract is also effective in decreasing the regulatory pool of hepatic cholesterol, in line with decreased blood and hepatic levels of cholesterol though modulation of mRNA expression levels of HMG-CoA reductase, ACAT, and FXR.

8.
J Hazard Mater ; 312: 200-207, 2016 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-27037474

RESUMO

Crude oil and refined petroleum products contain many polycyclic and heterocyclic aromatic hydrocarbons, in particular, alkylated PAHs. Although alkylated PAHs are found in significantly higher quantities than their corresponding unsubstituted PAHs, the most studies on the physico-chemical properties and toxicities of these compounds have been conducted on unsubstituted PAHs. In this study, we measured crucial physico-chemical properties (i.e., water solubility, partition coefficients between polydimethylsiloxane and water (KPDMSw), and partition coefficient between liposomes and water (Klipw)) of selected alkylated PAHs, and evaluated their toxicity using the luminescence inhibition of Aliivibrio fischeri and growth inhibition of Raphidocelis subcapitata. In general, the logarithms of these properties for alkylated PAHs showed good linear correlations with log Kow, as did those for unsubstituted PAHs. Changes in molecular symmetry on the introduction of alkyl groups on aromatic ring structure significantly altered water solubility. The inhibition of bacterial luminescence and algal growth by alkylated PAHs can be explained well by the baseline toxicity hypothesis, and good linear relationships between log Kow or log Klipw and log (1/EC50) were found.


Assuntos
Hidrocarbonetos Policíclicos Aromáticos/química , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Poluentes Químicos da Água/química , Poluentes Químicos da Água/toxicidade , Aliivibrio fischeri/efeitos dos fármacos , Clorófitas/efeitos dos fármacos , Petróleo , Solubilidade
9.
Environ Sci Technol ; 48(5): 2962-70, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24490901

RESUMO

A prediction model for estimating the ecotoxicity of the water-accommodated fraction (WAF) and water-soluble fraction (WSF) of heavy crude oil is proposed. Iranian heavy crude oil (IHC), one of the major components of the Hebei Spirit oil spill in Korea in 2007, was used as a model crude oil for the preparation of the WAF and the WSF. Luminescence inhibition of Vibrio fischeri was chosen as the model ecotoxicity test for evaluating the baseline toxicity of aromatic hydrocarbons in the IHC. The measured concentration of each chemical species in WAF and WSF agreed well with the predicted soluble concentration calculated using Raoult's law from the measured amount in the IHC. This indicates that the toxic potential of an oil mixture can be evaluated from the dissolved concentration of each species, which in turn, may be predicted from the composition of the crude or weathered oils. In addition, the contribution of each species in the mixture to the apparent luminescence inhibition by the WAF and the WSF was assessed using a concentration-addition model. The relative contributions of benzene, toluene, ethylbenzene, xylenes (BTEX), polycyclic aromatic hydrocarbons (PAHs), and alkylated PAHs in luminescence inhibition were estimated to be 76%, 2%, and 21%, respectively. It was further identified that C3- and C4-naphthalenes were the most important aromatic hydrocarbons responsible for baseline toxicity. This indicates that alkylated PAHs would be the major components of oil-spill residue. Further research is needed to evaluate the fate and ecotoxicity of alkylated PAHs.


Assuntos
Aliivibrio fischeri/efeitos dos fármacos , Hidrocarbonetos/toxicidade , Modelos Teóricos , Petróleo/toxicidade , Poluentes Químicos da Água/toxicidade , Aliivibrio fischeri/metabolismo , Hidrocarbonetos/análise , Hidrocarbonetos/química , Luminescência , Petróleo/análise , Solubilidade , Água/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química
10.
Ecotoxicol Environ Saf ; 94: 116-22, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23731864

RESUMO

Effects of individual petroleum hydrocarbons on the luminescence inhibition of Vibrio fischeri were evaluated according to a standard protocol to develop a quantitative structure-activity relationship and identify the apparent toxicity cutoff. Eighteen aromatic hydrocarbons, including benzene and its derivatives and polycyclic aromatic hydrocarbons (PAHs), were chosen as model compounds with their log K(ow) values between 2.7 and 6.4. The obtained values of 50 percent luminescence inhibition (EC50) showed a good linear correlation with log K(ow) up to ~5. However, toxic effects were not observed for more hydrophobic chemicals with log K(ow) value >5. The calculated chemical activities that caused EC50 were mostly between 0.01 and 0.1. This agrees with an earlier hypothesis concerning a chemical activity resulting the critical membrane concentration of aromatic hydrocarbons. The highest chemical activities for aromatic hydrocarbons with log K(ow) value >5 or melting point >100°C are <0.01 when they are spiked at their water solubility level according to the standard test protocol; this occurs for two primary reasons: (1) partitioning between organism and the test solution and (2) decreasing fugacity ratio with increasing melting point. Accordingly, luminescence inhibition by petroleum hydrocarbons is well explained by the baseline toxicity model. However, the apparent toxicity cutoff observed for single chemicals is not necessarily valid in a complex mixture, because baseline toxicity is regarded concentration additive.


Assuntos
Aliivibrio fischeri/fisiologia , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Poluentes Químicos da Água/toxicidade , Aliivibrio fischeri/efeitos dos fármacos , Relação Dose-Resposta a Droga , Luminescência , Medições Luminescentes , Petróleo/toxicidade , Relação Quantitativa Estrutura-Atividade , Solubilidade
11.
J Environ Monit ; 14(7): 1853-9, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22555157

RESUMO

Due to high usage of tetracycline antibiotics, concerns have been raised about their environmental fate. In this study, potential changes in the pseudo-first-order hydrolysis rate constants for three tetracyclines, tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC), were evaluated by measuring the rate constants in batch and column leaching experiments. The first-order hydrolysis rate constants were measured at pH 5, 7, and 9 using batch tests. The values were highest at pH 7 for all three tetracyclines (0.0030 ± 0.0004, 0.0042 ± 0.0001, and 0.0323 ± 0.0003 h(-1) for TC, OTC, and CTC, respectively), indicating relatively short environmental half-lives of tetracyclines. Interestingly, it was found that the rates of degradation of the parent tetracyclines were much faster when silica sand was present in a batch solution or when the solution was passed through a silica column. For example, the ratios of the first-order degradation rate constants obtained in the column experiments to those in batch experiments were 13.2, 2.1, and 2.0 for TC, OTC, and CTC at a volumetric flow rate of 0.08 mL h(-1), with an observed tendency for this ratio to increase with an increased flow rate. This indicates that the silica surface may serve as a catalyst for hydrolysis and that the actual environmental half-lives of tetracycline antibiotics could be shorter than those estimated from laboratory hydrolysis rate constants using the standard batch protocol. Furthermore, the toxicity of the column effluent containing hydrolysis metabolites was assessed using bioluminescence inhibition in Vibrio fischeri. It was estimated that the toxicity of the metabolites of CTC was lower than that of their parent compound, whereas the toxicity of metabolites of TC and OTC was as high as or higher than that of their parent compounds.


Assuntos
Antibacterianos/química , Dióxido de Silício/química , Tetraciclinas/química , Adsorção , Aliivibrio fischeri , Antibacterianos/toxicidade , Concentração de Íons de Hidrogênio , Hidrólise , Dióxido de Silício/toxicidade , Tetraciclinas/toxicidade
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