خيارات البحث
النتائج 191 - 200 من 2,459
Exposure of general population to PBDEs: A Progressive Total Diet Study in South Korea
2014
Nguyen, Khanh-Hoang | Pyo, Heesoo | Kim, Jongchul | Shin, EunSu | Chang, Yoon Seok
This study assessed the level of 24 polybrominated diphenyl ethers (PBDEs) in Korean foods following a Progressive Total Diet Study (TDS). The experiments comprised 96 types of dietetically representative foods, all were either cooked or edible raw. PBDEs were widely encountered in foodstuffs with the highest concentration in plant oils, fishes and shellfishes. Of all congeners tested for, BDE-47 was the most predominant and encountered in almost all food items except meats. The presence of nona-BDEs at significant levels indicated that Korean environments are still contaminated by deca-BDE. The daily dietary intake of PBDEs was estimated to be 63 ng d−1. The highest PBDEs intake was observed in the 19–39 year old group and gradually decreased as age increased. Our study suggests that the TDS approach using foods in the table-ready form should be used for a better estimation of dietary exposure to PBDEs.
اظهر المزيد [+] اقل [-]Uptake and elimination kinetics of metals in soil invertebrates: A review
2014
Ardestani, Masoud M. | Straalen, N. M. van | van Gestel, Cornelis A.M.
Uptake and elimination kinetics of metals in soil invertebrates are a function of both soil and organism properties. This study critically reviewed metal toxicokinetics in soil invertebrates and its potential use for assessing bioavailability. Uptake and elimination rate constants of different metals are summarized. Invertebrates have different strategies for essential and non-essential metals. As a consequence, different types of models must be applied to describe metal uptake and elimination kinetics. We discuss model parameters for each metal separately and show how they are influenced by exposure concentrations and by physiological properties of the organisms. Soil pH, cation exchange capacity, clay and organic matter content significantly affect uptake rates of non-essential metals in soil invertebrates. For essential metals, kinetics is hardly influenced by soil properties, but rather prone to physiological regulation mechanisms of the organisms. Our analysis illustrates that toxicokinetics can be a valuable measurement to assess bioavailability of soil-bound metals.
اظهر المزيد [+] اقل [-]Bioaccumulation of perfluoroalkyl compounds in midge (Chironomus riparius) larvae exposed to sediment
2014
Bertin, Delphine | Ferrari, Benoît J.D. | Labadie, Pierre | Sapin, Alexandre | Garric, Jeanne | Budzinski, Hélène | Houde, Magali | Babut, Marc
Midge larvae (Chironomus riparius) were exposed to sediments from a deposition sampled at a site along the Rhône River (France) downstream of an industrial site releasing various perfluorinated chemicals. This sediment is characterized by high concentrations of perfluoroundecanoic acid (PFUnA) and perfluorotridecanoic acid (PFTrDA) and a low perfluorooctane sulfonate (PFOS) concentration. Concentrations of 23 perfluoroalkyl compounds, including C4–C14 carboxylate acids, C4–C10 sulfonates, and seven precursors, were analyzed in overlying and pore water, sediment, and larvae. Midge larvae accumulated carboxylate acids (C11–C14), PFOS, and two precursors (perfluorooctane sulfonamide: FOSA and 6:2 fluorotelomer sulfonic acid, 6:2 FTSA). These substances accumulated mainly during the fourth instar larvae exponential growth phase. Accumulation of 6:2 FTSA, PFUnA, and PFOS occured via trophic and tegumentary routes. Other compounds mainly accumulated from food. Kinetics followed a partition model, from which uptake and elimination constants were derived.
اظهر المزيد [+] اقل [-]Atrazine contamination at the watershed scale and environmental factors affecting sampling rates of the polar organic chemical integrative sampler (POCIS)
2014
Dalton, Rebecca L. | Pick, Frances R. | Boutin, Céline | Saleem, Ammar
Polar organic chemical integrative samplers (POCIS) were used to estimate atrazine contamination at 24 stream/river sites located across a watershed with land use ranging from 6.7 to 97.4% annual crops and surface water nitrate concentrations ranging from 3 to 5404 μg/L. A gradient of atrazine contamination spanning two orders of magnitude was observed over two POCIS deployments of 28 d and was positively correlated with measures of agricultural intensity. The metabolite desisopropyl atrazine was used as a performance reference compound in field calibration studies. Sampling rates were similar between field sites but differed seasonally. Temperature had a significant effect on sampling rates while other environmental variables, including water velocity, appeared to have no effect on sampling rates. A performance reference compound approach showed potential in evaluating spatial and temporal differences in field sampling rates and as a tool for further understanding processes governing uptake of polar compounds by POCIS.
اظهر المزيد [+] اقل [-]Environmental externality and inequality in China: Current Status and future choices
2014
Zhao, Xiaoli | Zhang, Sufang | Fan, Chunyang
Along with China's rapid economic growth, the environmental externality in the country is getting more and more serious. China's environmental externality is accompanied by environmental inequality, which presents two characteristics: First, the health loss caused by environmental externality is concentrated in the elderly and children. We take Beijing as an empirical analysis to conclude that children (0–4 years old) are the largest group suffered from respiratory disease; while the seniors are the largest group suffered from cardiovascular disease. Second, China's environmental inequality is mainly caused by the transfer of industries from urban to rural areas/suburbs. The villagers in poor rural areas are the biggest victims. China's environmental inequality is reflected particularly by the phenomenon of “cancer villages” which has existed ever since the end of 1970s. Finally, policy recommendations are provided for reducing China's environmental externality and inequality.
اظهر المزيد [+] اقل [-]Mapping polycyclic aromatic hydrocarbon and total toxicity equivalent soil concentrations by visible and near-infrared spectroscopy
2014
Okparanma, Reuben N. | Coulon, Frederic | Mayr, Thomas | Mouazen, Abdul M.
In this study, we used data from spectroscopic models based on visible and near-infrared (vis-NIR; 350–2500 nm) diffuse reflectance spectroscopy to develop soil maps of polycyclic aromatic hydrocarbons (PAHs) and total toxicity equivalent concentrations (TTEC) of the PAH mixture. The TTEC maps were then used for hazard assessment of three petroleum release sites in the Niger Delta province of Nigeria (5.317°N, 6.467°E). As the paired t-test revealed, there were non-significant (p > 0.05) differences between soil maps of PAH and TTEC developed with chemically measured and vis-NIR-predicted data. Comparison maps of PAH showed a slight to moderate agreement between measured and predicted data (Kappa coefficient = 0.19–0.56). Using proposed generic assessment criteria, hazard assessment showed that the degree of action for site-specific risk assessment and/or remediation is similar for both measurement methods. This demonstrates that the vis-NIR method may be useful for monitoring hydrocarbon contamination in a petroleum release site.
اظهر المزيد [+] اقل [-]Uptake, localization and clearance of quantum dots in ciliated protozoa Tetrahymena thermophila
2014
Mortimer, Monika | Kahru, Anne | Slaveykova, Vera I.
Protozoa as phagocytizing cells have been shown to integrate engineered nanoparticles (NPs), while the mechanism, dynamics and extent of such uptake are unclear. Here our fluorescence microscopy data showed that CdSe/ZnS quantum dots (QDs) with primary size of 12 nm were readily phagocytized into the food vacuoles of Tetrahymena thermophila in a time- and dose-dependent manner. Twenty hours after the exposure to QDs in sublethal concentration the clearance of the QDs from the cells was incomplete suggesting that phagocytosis of QDs into food vacuoles was not the only pathway of uptake by T. thermophila. This was further proven by the results that the inhibition of phagocytosis did not block the internalization of QDs into protozoans. This study provides a new insight into uptake and cellular trafficking of subtoxic concentrations of nanoparticles that may, due to prolonged retention times in the cells, pose risks by potentially becoming available to higher trophic levels.
اظهر المزيد [+] اقل [-]Interrogating trees for isotopic archives of atmospheric sulphur deposition and comparison to speleothem records
2014
Wynn, P.M. | Loader, N.J. | Fairchild, I.J.
Palaeorecords which depict changes in sulphur dynamics form an invaluable resource for recording atmospheric pollution. Tree rings constitute an archive that are ubiquitously available and can be absolutely dated, providing the potential to explore local- to regional-scale trends in sulphur availability. Rapid isotopic analysis by a novel “on-line” method using elemental analyser isotope ratio mass spectrometry (EA-IRMS) is developed, achieving sample precision of <0.4‰ using sample sizes of 40 mg wood powder. Tree cores from NE Italy show trends in pollution, evidenced through increasing concentrations of sulphur towards the youngest growth, and inverse trends in sulphur isotopes differentiating modern growth with light sulphur isotopes (+0.7‰) from pre-industrial growth (+7.5‰) influenced by bedrock composition. Comparison with speleothem records from the same location demonstrate replication, albeit offset in isotopic value due to groundwater storage. Using EA-IRMS, tree ring archives form a valuable resource for understanding local- to regional-scale sulphur pollution dynamics.
اظهر المزيد [+] اقل [-]Setting ozone critical levels for protecting horticultural Mediterranean crops: Case study of tomato
2014
González Fernández, I. | Calvo, E. | Gerosa, G. | Bermejo, V. | Marzuoli, R. | Calatayud, V. | Alonso, R.
Seven experiments carried out in Italy and Spain have been used to parameterising a stomatal conductance model and establishing exposure– and dose–response relationships for yield and quality of tomato with the main goal of setting O3 critical levels (CLe). CLe with confidence intervals, between brackets, were set at an accumulated hourly O3 exposure over 40 nl l−1, AOT40 = 8.4 (1.2, 15.6) ppm h and a phytotoxic ozone dose above a threshold of 6 nmol m−2 s−1, POD6 = 2.7 (0.8, 4.6) mmol m−2 for yield and AOT40 = 18.7 (8.5, 28.8) ppm h and POD6 = 4.1 (2.0, 6.2) mmol m−2 for quality, both indices performing equally well. CLe confidence intervals provide information on the quality of the dataset and should be included in future calculations of O3 CLe for improving current methodologies.These CLe, derived for sensitive tomato cultivars, should not be applied for quantifying O3-induced losses at the risk of making important overestimations of the economical losses associated with O3 pollution.
اظهر المزيد [+] اقل [-]Chemical and biological characterization of air particulate matter 2.5, collected from five cities in China
2014
Leung, P.Y. | Wan, H.T. | Billah, M.B. | Cao, J.J. | Ho, K.F. | Wong, Chris K.C.
Fifteen polycyclic aromatic hydrocarbons (PAHs) in PM2.5 samples collected in five different cities (Hong Kong (HK), Guangzhou (GZ), Xiamen (XM), Xi'an (XA) and Beijing (BJ)) in China in the winter 2012–12 were analyzed by gas chromatography-mass spectrometry. The biological effects of organic extracts were assayed using the human bronchial epithelial cells BEAS-2B. All sixteen priority PAHs can be found in the PM2.5 samples of XA and BJ, but not in HK, GZ and XM, demonstrating the differential spatial source and distribution of PAHs. Our results showed that the total PAHs ranged from 3.35 to 80.45 ng/m3 air, leading by BJ, followed by XA, XM, GZ and HK. In the cell culture study, transcript levels of pro-inflammatory cytokine interleukin-6 (IL-6), CYP1A1 and CYP1B1 were found to be induced in the treatment. The cells exposed to extracts from XA and BJ demonstrated significant migratory activities, indicating a sign of increase of tumorigenicity.
اظهر المزيد [+] اقل [-]