Comparison of the exposure assessment of di(2-ethylhexyl) phthalate between the PBPK model-based reverse dosimetry and scenario-based analysis: A Korean general population study.

Di (2-ethylhexyl) phthalate (DEHP), classified as a reproductive toxicant, is a ubiquitous pollutant in foodstuffs, dust, and commercial products. In this study, to provide a useful cross-check on the accuracy of the exposure assessment, the estimated daily intake of DEHP was compared using reverse dosimetry with a physiologically-based pharmacokinetic (PBPK) model and a scenario-based probabilistic estimation model for six subpopulations in Korea. For reverse dosimetry analysis, the concentrations of urinary DEHP metabolites, namely mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl)phthalate (MEOHP), from three human biomonitoring program datasets were used. For the scenario-based model, we evaluated the various exposure sources of DEHP, including diet, air, indoor dust, soil, and personal care products (PCPs), and also determined its levels based on the literature review and measurements of indoor dust. The DEHP exposure doses using both exposure assessment approaches were similar in all cases, except for the 95th percentile exposure doses in toddlers (1-2 years) and young children (3-6 years). The PBPK-reverse dosimetry estimated daily intakes at the 95th percentile ranged between 22.53 and 29.90 µg/kg/day for toddlers and young children. These exceeded the reference dose (RfD) of 20 µg/kg bw/day of the US Environmental Protection Agency (EPA) based on the increased relative liver weight. Although, food was considered the primary source of DEHP, contributing to a total exposure of 50.8-75.1%, the effect of exposure to indoor dust should not be overlooked. The occurrence of high levels of DEHP in indoor dust collected from Korean homes suggests the use of a wide variety of consumer products containing DEHP. Furthermore, more attention should be paid to the high exposure levels of DEHP, especially in young children. Therefore, it is necessary to perform continuous monitoring of the indoor dust, consumer products, and the body burden of children.

Effects of the chorion on the developmental toxicity of organophosphate esters in zebrafish embryos.

Many toxicological studies have utilized zebrafish embryos to investigate the developmental toxicity of organophosphate esters (OPEs). However, in respect of the presence or absence of the chorion, a consistent experimental methodology has yet to be developed. In this study, we used a fixed exposure scheme to compare the developmental toxicities of six major OPEs in chorionated and dechorionated zebrafish embryos. Removal of the chorion increased sensitivity to OPEs: we found higher incidence of mortality and malformation in dechorionated embryos. In a behavioral assay, the locomotive activity of zebrafish larvae was consistently inhibited by OPEs except tris (1-chloropropyl) phosphate regardless of chorion presence. However, at the molecular level, the expression of ZHE1 and mmp9 was affected by the presence of the chorion in zebrafish embryos exposed to tributyl phosphate and triphenyl phosphate (TPHP), respectively. Furthermore, in zebrafish embryos exposed to TPHP, the increased expression of miR-137 and miR-141 was abolished by the presence of the chorion. Our results demonstrate for the first time that the presence of the chorion influences phenotypic morbidity, organismal behavior, and gene expression in zebrafish embryos exposed to chemicals; thus, we suggest that dechorionation is desirable for exploring the toxicity mechanisms that underlie effects of chemical exposure.

The occurrence and distribution of polychlorinated naphthalenes (PCNs), focusing on tissue-specific bioaccumulation in crucian carp in South Korea.

The occurrence and distribution of 41 congeners of polychlorinated naphthalenes (PCNs) were investigated in major tissues of crucian carp (muscle, gonad, liver, and blood) and in river sediment to assess the bioaccumulation potential of PCNs. The total PCN concentrations in sediment ranged from 4.37 to 19.5 pg/g dry weight (dw), mainly comprising CN-13, CN-33/34/37, and CN-38/40. Among fish tissues, higher PCN concentrations were observed in the gonads (29.6 ±â€¯10.3 pg/g wet weight, ww) and liver (25.7 ±â€¯4.35 pg/g ww) of crucian carp than in the muscle (2.17 ±â€¯0.68 pg/g ww). CN-28/43, CN-33/34/37, CN-42, CN-52/60, CN-53/55, and CN-66/67 congeners were detected most frequently and had the highest concentration among all crucian carp tissues. We investigated the association between the PCN concentration in each tissue (muscle, liver, and gonad) and the size of the fish (total length and weight) and found positive correlations between the PCN concentration in the gonads and the total length and weight (p < 0.05, Spearman correlation).

Trophic transfer of citrate, PVP coated silver nanomaterials, and silver ions in a paddy microcosm.

We used replicated paddy microcosm systems to estimate the tropic transfer of citrate-coated silver nanoparticles (AgNP citrate), polyvinylpyrrolidone (PVP)-coated AgNP (AgNP PVP), and silver ions (AgNO3) for 14 days under two exposure regimes (a single high-dose exposure; 60 µg L-1 and a sequential low-dose exposure at 1 h, 4 days and 9 days; 20 µg L-1 × 3 = 60 µg L-1). Most Ag ions from AgNO3 had dispersed in the water and precipitated partly on the sediment, whereas the two Ag NPs rapidly coagulated and precipitated on the sediment. The bioconcentration factors (BCFs) of Ag from AgNPs and AgNO3 in Chinese muddy loaches and biofilms were higher than those of river snails in both exposure conditions. These BCFs were more prominent for 14 days exposure (7.30 for Chinese muddy loach; 4.48 for biofilm) in the low-dose group than in the single high-dose group. Their retention of AgNPs and Ag ions differed between the two exposure conditions, and uptake and elimination kinetics of Ag significantly differed between AgNP citrate and AgNP PVP in the sequential low-dose exposure. Stable isotopes analyses indicated that the trophic levels between Chinese muddy loaches and biofilms and between river snails and biofilms were 2.37 and 2.27, respectively. The biomagnification factors (BMFs) of AgNPs and AgNO3 between Chinese muddy loaches and biofilms were significantly higher than those between river snails and biofilms under both exposure settings. The BMFs of AgNP citrate and AgNO3 between Chinese muddy loaches and biofilms were greater than those of AgNP PVP for 14 days in the single high-dose group, whereas the BMFs of AgNP PVP were greater than those of AgNP citrate and AgNO3 in the sequential low-dose group. These microcosm data suggest that AgNPs have the potential to impact on ecological receptors and food chains.

Comparison of Real Time Nanoparticle Monitoring Instruments in the Workplaces.

BACKGROUND: Relationships among portable scanning mobility particle sizer (P-SMPS), condensation particle counter (CPC), and surface area monitor (SAM), which are different metric measurement devices, were investigated, and two widely used research grade (RG)-SMPSs were compared to harmonize the measurement protocols. METHODS: Pearson correlation analysis was performed to compare the relation between P-SMPS, CPC, and SAM and two common RG-SMPS. RESULTS: For laboratory and engineered nanoparticle (ENP) workplaces, correlation among devices showed good relationships. Correlation among devices was fair in unintended nanoparticle (UNP)-emitting workplaces. This is partly explained by the fact that shape of particles was not spherical, although calibration of sampling instruments was performed using spherical particles and the concentration was very high at the UNP workplaces to allow them to aggregate more easily. Chain-like particles were found by scanning electron microscope in UNP workplaces. The CPC or SAM could be used as an alternative instrument instead of SMPS at the ENP-handling workplaces. At the UNP workplaces, where concentration is high, real-time instruments should be used with caution. There are significant differences between the two SMPSs tested. TSI SMPS showed about 20% higher concentration than the Grimm SMPS in all workplaces. CONCLUSIONS: For nanoparticle measurement, CPC and SAM might be useful to find source of emission at laboratory and ENP workplaces instead of P-SMPS in the first stage. An SMPS is required to measure with high accuracy. Caution is necessary when comparing data from different nanoparticle measurement devices and RG-SMPSs.

Transport, retention, and long-term release behavior of ZnO nanoparticle aggregates in saturated quartz sand: Role of solution pH and biofilm coating.

The transport, retention, and long-term release of zinc oxide nanoparticle aggregates (denoted below as ZnO-NPs) were investigated in saturated, bare and biofilm (Pseudomonas putida) coated sand packed columns. Almost complete retention of ZnO-NPs occurred in bare and biofilm coated sand when the influent solution pH was 9 and the ionic strength (IS) was 0.1 or 10 mM NaCl, and the retention profiles were always hyper-exponential. Increasing the solution IS and biofilm coating produced enhanced retention of ZnO-NPs near the column inlet. The enhanced NPs retention at high IS was attributed to more favorable NP-silica and NP-NP interactions; this was consistent with the interaction energy calculations. Meanwhile, the greater NPs retention in the presence of biofilm was attributed to larger roughness heights which alter the mass transfer rate, the interaction energy profile, and lever arms associated with the torque balance; e.g., scanning electron and atomic force microscopy was used to determine roughness heights of 33.4 nm and 97.8 nm for bare sand and biofilm-coated sand, respectively. Interactions between NPs and extracellular polymeric substances may have also contributed to enhanced NP retention in biofilm-coated sand at low IS. The long-term release of retained ZnO-NPs was subsequently investigated by continuously injecting NP-free solution at pH 6, 9, or 10 and keeping the IS constant at 10 mM. The amount and rate of retained ZnO-NP removal was strongly dependent on the solution pH. Specifically, almost complete removal of retained ZnO-NPs was observed after 627 pore volumes when the solution pH was 6, whereas much less Zn was recovered when the eluting solution pH was buffered to pH = 9 and especially 10. This long-term removal was attributed to pH-dependent dissolution of retained ZnO-NPs because: (i) the solubility of ZnO-NPs increases with decreasing pH; and (ii) ZnO-NPs were not detected in the effluent. The presence of biofilm also decreased the initial rate and amount of dissolution and the subsequent transport of Zn(2+) due to the strong Zn(2+) re-adsorption to the biofilm. Our study indicates that dissolution will eventually lead to the complete removal of retained ZnO-NPs and the transport of toxic Zn(2+) ions in groundwater environments with pH ranges of 5-9.

Serum and ultrastructure responses of common carp (Cyprinus carpio L.) during long-term exposure to zinc oxide nanoparticles.

The uptake of nanoparticles by aquatic organisms such as fish has raised concerns about the possible adverse effects of nanoparticles (NPs). In this study, we aimed to evaluate the toxicological effects in juvenile common carp exposed to zinc oxide nanoparticles (ZnO-NPs) for 12 weeks. The carp were exposed to 0 (control), 0.1, 0.3, 0.8, and 2.4mg/L of ZnO-NPs under a flow-through exposure system. Fish were sampled at 0, 4, 8, and 12 weeks to test for zinc in the test water and blood, and biochemistry analysis; further, they were sampled at 12 weeks to observe ultrastructural changes in the liver, kidney, and gill. In the organic serum, changes in the glutamic pyruvic transaminase/alanine aminotransferase (GPT/ALT) and glutamic oxaloacetic transaminase/aspartate aminotransferase (GOT/AST) levels were significant, but changes in the lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) levels were not significantly different across all exposure periods. In the inorganic serum, the magnesium (Mg), inorganic phosphorus (IP), sodium (Na(+)), and chloride (Cl(-)) levels were significantly different in the exposure group and across exposure periods. However, calcium (Ca) and potassium (K(+)) levels were not significantly different. In the enzyme serum, the glucose (GLU) level significantly increased for the highest exposure group, but the total cholesterol (TCHO), triglyceride (Tg), and total protein (TP) levels were not significantly different during the exposure period. Ultrastructural changes in the liver induced changes in the black granules (of various sizes) in the lysosomes, indistinct nucleus membrane, and non-spherical nucleus. In the kidney, some mild changes were observed in the size and number of the lysosomes in the renal tubule. Desquamation and hypertrophy of pavement epithelial cells and vacuolation in the cytoplasm of the chloride cells were observed in the gill. Nanoparticles were also observed in the red blood cells, cytoplasm of all tissues, and glomerulus of the kidney. The observed changes in the serum and tissues may provide useful information regarding environmental conditions and risk assessments of aquatic organisms.

Perfluorinated alkyl substances in water, sediment, plankton and fish from Korean rivers and lakes: a nationwide survey.

Water, sediment, plankton, and blood and liver tissues of crucian carp (Carassius auratus) and mandarin fish (Siniperca scherzeri) were collected from six major rivers and lakes in South Korea (including Namhan River, Bukhan River, Nakdong River, Nam River, Yeongsan River and Sangsa Lake) and analyzed for perfluorinated alkyl substances (PFASs). Perfluorooctane sulfonate (PFOS) was consistently detected at the greatest concentrations in all media surveyed with the maximum concentration in water of 15 ng L(-1) and in biota of 234 ng mL(-1) (fish blood). A general ascending order of PFAS concentration of water0.80, p<0.001) were observed between PFOS concentration in blood and liver tissues of both crucian carp and mandarin fish. This result suggests that blood can be used for nonlethal monitoring of PFOS in fish. Overall, the rank order of mean bioconcentration factors (BCFs) of PFOS in biota was; phytoplankton (196 L/kg)

Effects of ionization on the toxicity of silver nanoparticles to Japanese medaka (Oryzias latipes) embryos.

Increase in the use of manufactured nanomaterials (NMs) has led to concerns about the environmental impacts. Especially, hazard of metal-based NMs is more severe due to ions released from surface by water quality parameters and physicochemical properties after entering into the water environment. However, little is known about the effects of ionization on the toxicity of metal-based NMs in the water environment. To address this question, we prepared the suspensions of silver nanoparticles (AgNP) at 25 µg L(-1) containing different concentrations of Ag(+) (5, 10, 20, 45, and 75% Ag(+) to total Ag), and evaluated their toxicity to Japanese medaka (Oryzias latipes) embryos. Higher Ag(+) ratios in the AgNP suspension, suggesting the lower number of particles, led to the higher adverse effects on embryos and sac-fries. In addition, histopathology analysis revealed that AgNPs penetrated through chorion of eggs and skin membrane, and were distributed into the tissues. The results imply that the ionization could decrease the toxicity of metal-based NMs in the water environment.

Hexabromocyclododecanes in crucian carp and sediment from the major rivers in Korea.

The concentration of hexabromocyclododecanes (HBCDs) was measured in crucian carp muscles and eggs and in surrounding sediments collected from the 3 major rivers in Korea. HBCDs were detected in all carp and sediment samples, indicating widespread contamination of this area by HBCD flame retardants. The ∑HBCD (sum of α-, ß-, and γ-HBCDs) concentrations ranged from 0.19 to 13 ng g(-1)dry wt in sediments, 1.7 to 7.2 ng g(-1)lipid wt in carp eggs, and 4.8 to 6.6 ng g(-1)lipid wt in the muscle of carp. The α-diastereomer predominated in the crucian carp and γ-diastereomer predominated in sediments, accounting for 76% and 77% to the ∑HBCD, respectively. The ∑HBCD concentrations in carp and sediment samples collected along the rivers were higher than those in samples collected from an isolated pond, suggesting that the rivers are likely contaminated by HBCDs from the upstream or the environment surrounding the rivers. The diastereomer ratios in carp were different from those in commercial mixtures due to the enrichment of α-diastereomer in carp. The origin of this transition, however, is yet not known, since various transformation processes can lead to a change from the diastereomer ratio in commercial mixtures to that observed in the environment.

Stepwise embryonic toxicity of silver nanoparticles on Oryzias latipes.

The developmental toxicity of silver nanoparticles (AgNPs) was investigated following exposure of Oryzias latipes (medaka) embryos to 0.1-1 mg/L of homogeneously dispersed AgNPs for 14 days. During this period, developmental endpoints, including lethality, heart rate, and hatching rate, were evaluated by microscopy for different stages of medaka embryonic development. To compare toxic sensitivity, acute adult toxicity was assessed. There was no difference in acute lethal toxicity between embryo and adult medaka. Interestingly, we found that the increase in stepwise toxicity was dependent on the developmental stage of the embryo. Lethal embryonic toxicity increased from exposure days 1 to 3 and exposure days 5 to 8, whereas there was no change from exposure days 3 to 5. In addition, 7 d exposure to 0.8 mg/L AgNPs resulted in significant heart beat retardation in medaka embryos. AgNPs also caused a dose-dependent decrease in the hatching rate and body length of larvae. These results indicate that AgNP exposure causes severe developmental toxicity to medaka embryos and that toxicity levels are enhanced at certain developmental stages, which should be taken into consideration in assessments of metallic NPs toxicity to embryos.

Effect of dispersion stability on the deposition of citrate-capped silver nanoparticles in natural soils.

Although little is known about the behavior of engineered nanomaterials after exposure to terrestrial areas, recent studies indicate that silver nanoparticles (AgNPs) can perturb the soil environment due to their biocidal and catalytic properties. The fundamental evaluation of the environmental fate of AgNPs would be a significant step toward a comprehensive understanding of the harmful effects of such particles on ecosystems. Therefore, from an eco-toxicological perspective, the estimation of AgNP behavior in soil should be investigated. Among the various environmental characteristics, the deposition of nanoparticles in the soil constitute is a critical step in their migration into surface or groundwater and interaction with organisms, which is determined by the stability of aqueous dispersions in a soil micro-environment. In the present study, we observed the aggregation and deposition of AgNPs to natural soil surfaces by comparing the partitioning of AgNPs in a soil/water interface with that of Ag+ ion. Both AgNPs and Ag+ ion were selectively quantified by means of inductively coupled plasma (ICP) spectrometry and an ion-selective electrode (ISE). We interpreted the partitioning of AgNPs and Ag+ ion using the Freundlich isotherm and the findings indicate that AgNPs with reduced dispersion stability in a soil micro-environment were aggregated and deposited on the surface of natural soil. This study provides a fundamental basis for understanding the deposition of AgNPs, which will enable their accumulation and mobility in a soil environment to be predicted.

Serum kinetics, distribution and excretion of silver in rabbits following 28 days after a single intravenous injection of silver nanoparticles.

Serum kinetics, tissue distribution, and excretion of citrate-coated silver nanoparticles (AgNPs) were investigated in rabbits (n = 4) up to 28 days after a single intravenous injection. Following a single injection of AgNPs, the AUC(last) was reported to be 3.65 ± 0.68 µg·day/ml in 5 mg/kg-treated group and 0.90 ± 0.16 µg·day/ml in 0.5 mg/kg-treated group, respectively. The accumulation of silver was observed in all the tested organs including liver, kidney, spleen, lung, brain, testis, and thymus at 1 day, 7 day, and 28 day of measurement. The liver and spleen seemed to be the major targets because of high accumulation of silver. Excretion via feces and urine was also monitored during the entire experimental period. Unexpectedly, much more excretion of silver occurred via feces than through urine after an intravenous injection, which suggests biliary excretion of AgNPs. General toxicity was analyzed and histopathological changes were also evaluated.

Toxicity of citrate-capped silver nanoparticles in common carp (Cyprinus carpio).

Juvenile common carp (Cyprinus carpio) were used as a model to investigate acute toxicity and oxidative stress caused by silver nanoparticles (Ag-NPs). The fish were exposed to different concentrations of Ag-NPs for 48 h and 96 h. After exposure, antioxidant enzyme levels were measured, including glutathione-S-transferase (GST), superoxidase dismutase, and catalase (CAT). Other biochemical parameters and histological abnormalities in different tissues (i.e., the liver, gills, and brain) were also examined. The results showed that Ag-NPs agglomerated in freshwater used during the exposure experiments, with particle size remaining <100 nm. Ag-NPs had no lethal effect on fish after 4 days of exposure. Biochemical analysis showed that enzymatic activities in the brain of the fish exposed to 200 µg/L of Ag-NPs were significantly reduced. Varied antioxidant enzyme activity was recorded in the liver and gills. Varied antioxidant enzyme activity was recorded for CAT in the liver and GST in the gills of the fish. However, the recovery rate of fish exposed to 200 µg/L of Ag-NPs was slower than when lower particle concentrations were used. Other biochemical indices showed no significant difference, except for NH(3) and blood urea nitrogen concentrations in fish exposed to 50 µg/L of Ag-NPs. This study provides new evidence about the effects of nanoparticles on aquatic organisms.

Effects of chlorine on the decrease of estrogenic chemicals.

The effects of chlorination on the elimination of three estrogenic chemicals such as 17beta-estradiol, nonylphenol and bis-phenol A were investigated using yeast two-hybrid assay (YTA), estrogen receptor (ER) competition assay (ER-CA), and high-performance liquid chromatography/mass spectrometry (LC/MS). The results of YTA, ER-CA and the analysis of LC/MS indicated that the estrogenic activity of the above-mentioned three endocrine disruptors were significantly reduced as a result of chlorination. The decrease in estrogenic activity paralleled a decrease in estrogenic chemicals under the influence of free chlorine. One common characteristic of estrogenic chemicals is the presence of a phenolic ring. Considering that a phenolic ring is likely to undergo some sort of transformation in an aqueous chlorination solution, the above-mentioned results may be applied to the rest of the estrogenic chemicals in natural waters.