Arsenic contamination in the freshwater fish ponds of Pearl River Delta: bioaccumulation and health risk assessment

Effects of seasonal temperature regimes: Does Cyprinus carpio act as a health hazard during the construction of Suki Kinari hydropower project on Kunhar River in Pakistan?

The main purpose of the current study was to assess the levels of trace elements (iron, lead, zinc, copper, and manganese) in both water and fish muscles of common carp (Cyprinus carpio) in the Kunhar River during the development of the Suki Kinari hydropower project (SKHPP). Additionally, the aim was to shed light on the potential health hazards associated with the consumption of fish by residents. Surface water and fish (muscle and liver) from ten specific sampling locations in the Mansehra district (affected by an SKHPP) along the river were examined to determine the levels of trace elements. The findings divulged that the water at all locations exhibited concentration levels of iron (Fe), lead (Pb), and manganese (Mn) that surpassed the benchmarks established by the World Health Organization in 2011. Conversely, the concentration levels of copper (Cu) and zinc (Zn) fell beneath the stipulated standards. Moreover, the concentrations of Mn, Zn, and Pb were found to be excessively high. The findings presented in the present study offer a comprehensive comprehension of the spatial and distribution characteristics of trace elements in both water and fish species along the Kunhar River, taking into consideration the impact of the SKHPP. Additionally, our data emphasize the potential health hazards that may arise from the prolonged consumption of fish by the local population.

Trophic transfer patterns of arsenic in freshwater ecosystem layers in arsenic-endemic Ganges Delta and its potential human health risk

Arsenic (As) is a toxic environmental contaminant with global public health concern. In aquatic ecosystems, the quantification of total As is restricted chiefly to the individual organisms. The present study has quantified the total As in different trophic layers (sediment-water-phytoplankton-periphyton-zooplankton-fish-gastropod-hydrophytes) of lentic freshwater ecosystems. As transfer pathways quantifying the transmission rate across trophic-level compartmental route were delineated using a novel model-based approach along with its potential contamination risk to humans. Lentic water bodies from Indo-Gangetic region, a core area of groundwater As, were selected for the present investigation. The study revealed that among the lower biota, zooplankton were the highest accumulator of total As (5554-11,564 µg kg-1) with magnification (rate = 1.129) of the metalloid, followed by phytoplankton (2579-6865 µg kg-1) and periphytic biofilm (1075 to 4382 µg kg -1). Muscle tissue of zooplanktivore Labeo catla is found to store higher As (80-115 µg kg-1 w.w.) compared to bottom-dwelling omnivore Cirrhinus mrigala (58-92 µg kg-1 w.w.). Whereas, Amblypharyngodon mola has accumulated higher As (203-319 µg kg-1 w.w.) than Puntius sophore (30-98 µg kg-1 w.w.) that raised further concern. The hepatic concentration indicated arsenic-mediated stress based on As stress index (threshold value = 1). Mrigal and Mola showed significant biomagnification among fishes while biodiminution was observed in Catla, Bata, Rohu and Punti. All the studied fishes were under the arsenic mediated stress. In the 'sediment-water-periphytic biofilm-gastropod' compartment, the direct grazing accumulation was higher (rate = 0.618) than the indirect path (rate = 0.587). Stems of edible freshwater macrophytes accumulated lesser As (32-190 µg kg-1 d.w.) than roots (292-946 µg kg-1 d.w.) and leaves (62-231 µg kg-1 d.w.). The target cancer risk (TCR) revealed a greater concern for adults consuming edible macrophyte regularly. Similarly, the varied level of target hazard quotient and TCR for adults consuming fishes from these waterbodies further speculated significant health concerns. The trophic transfer rate of environmental As in soil-water-biota level at an increasing trophic guild and consumer risk analysis have been unravelled for the first time in the Indo-Gangetic plains, which will be helpful for the strategic mitigation of As contamination.

Arsenic speciation in freshwater fish: challenges and research needs

Food and water are the main sources of human exposure to arsenic. It is important to determine arsenic species in food because the toxicities of arsenic vary greatly with its chemical speciation. Extensive research has focused on high concentrations of arsenic species in marine organisms. The concentrations of arsenic species in freshwater fish are much lower, and their determination presents analytical challenges. In this review, we summarize the current state of knowledge on arsenic speciation in freshwater fish and discuss challenges and research needs. Fish samples are typically homogenized, and arsenic species are extracted using water/methanol with the assistance of sonication and enzyme treatment. Arsenic species in the extracts are commonly separated using high-performance liquid chromatography (HPLC) and detected using inductively coupled plasma mass spectrometry (ICPMS). Electrospray ionization tandem mass spectrometry, used in combination with HPLC and ICPMS, provides complementary information for the identification and characterization of arsenic species. The methods and perspectives discussed in this review, covering sample preparation, chromatography separation, and mass spectrometry detection, are directed to arsenic speciation in freshwater fish and applicable to studies of other food items. Despite progress made in arsenic speciation analysis, a large fraction of the total arsenic in freshwater fish remains unidentified. It is challenging to identify and quantify arsenic species present in complex sample matrices at very low concentrations. Further research is needed to improve the extraction efficiency, chromatographic resolution, detection sensitivity, and characterization capability.

Heavy Metal Pollution in Aquaculture: Sources, Impacts and Mitigation Techniques

Aquaculture is one of the fastest growing agro-industries as it presently accounts for nearly 50% of all fish for direct human consumption and 43% of total seafood supply. Fish provide about 20% average daily intake of animal protein for about 3.2 billion people globally. The treatment of aquaculture in recent years for the mitigation of heavy metals and other contaminants has been gaining traction due to the benefits of aquaculture to both man and the environment. This paper provides a review of the sources, impacts, and the various methods that have been deployed in recent years by various researchers for the treatment of heavy metal contaminated aquaculture. Related works of literature were obtained and compiled from academic search databases and were carefully analysed in this study. The dangers these metals pose to the sustainability of aquaculture were studied in this review. Studies indicate that some heavy metals, such as mercury, lead, and cadmium, due to their long-term persistence in the environment, allow them to accumulate in the food chain. Mitigation techniques such as adsorption, bio-sorption, and phytoremediation have been deployed for the treatment of heavy metal contaminated aquaculture. Some research gaps were also highlighted which could form the basis for future research, such as research centred on the effects of these metals on the embryonic development of aquaculture organisms and the alterations the metals caused in their stages of development.

Arsenic Bioaccumulation and Identification of Low-Arsenic-Accumulating Food Fishes for Aquaculture in Arsenic-Contaminated Ponds and Associated Aquatic Ecosystems

Arsenic-contaminated food including farmed fish is one of the main routes of human exposure. Fish farmed in contaminated environment accumulates arsenic in different tissues with great variability. Thus, it is utmost important to quantify the risk associated with different farmed fish species in arsenic-contaminated aquaculture systems. In the present study, arsenic content was measured in twelve fish species (Labeo rohita, L. catla, Cirrhinus mrigala, Oreochromis niloticus, O. mossambicus, Liza tade, Puntius javanicus, L. calbasu, Glossogobius giuris, Macrobrachium rosenbergii, Ctenopharyngodon idella, and Bellamya bengalensis (gastropod)) collected from arsenic-contaminated aquaculture systems. Among the studied finfishes, C. idella was found to accumulate the lowest amount of arsenic (< 0.05 ± 0.00 mg kg^-1) whereas the highest accumulation was noticed in O. mossambicus (1.0 ± 0.18 mg kg^-1). However, the estimated carcinogenic and non-carcinogenic risks of human were found to be low for all the studied fishes. The calculated target hazard quotient (THQ) value for adults ranged from 0.01 to 0.08 whereas for children it ranged from 0.05 to 0.27 for low-arsenic-accumulating fishes (arsenic conc. < 0.5 mg kg^-1). Based on these findings, C. mrigala, C. idella, and M. rosenbergii could be recommended as the candidate species for aquaculture in the arsenic-contaminated areas as farming of the low-arsenic-accumulating food fishes would also lower the risk of human exposure through food chain.

Occurrence of microplastic in the water of different types of aquaculture ponds in an important lakeside freshwater aquaculture area of China

Aquaculture ponds are exposed to numerous potential microplastic sources, but studies on their microplastic pollution are still limited. Various culture species may influence the occurrence of microplastic in ponds. In the present study, the occurrence of microplastics was studied in aquaculture ponds for fish, crayfish, and crab, as well as in the natural lake near the aquaculture area around the Honghu Lake, which is the principal freshwater aquaculture area of China. The microplastic abundances ranged from 87 items/m³ to 750 items/m³ in the aquaculture ponds, and 117 items/m³ to 533 items/m³ in the lake. The crab ponds contained higher abundances of microplastics than fish ponds and the nearby natural lakes. Microplastics that were between 100 and 500 μm and larger than 1000 μm in size were predominant in the ponds and nearby lakes, whereas the proportion of microplastics that were smaller than 100 μm was higher in crab ponds than those in other ponds. Fragments and fibers were the predominant shapes of microplastics in the ponds. The proportion of smaller microplastics in the ponds had a positive correlation with the proportion of fragment microplastics. The results of this study implied that differences in the use of plastics in various types of aquaculture ponds might affect their microplastic pollution characteristics. Microplastics discharged from ponds to nearby lakes through drainage processes require attention in further studies.

Arsenic in the top predators sailfish (Istiophorus platypterus) and dolphinfish (Coryphaena hippurus) off the southeastern Gulf of California

Distribution of arsenic (As) in tissues and gonads of the Indo-Pacific sailfish Istiophorus platypterus and the dolphinfish Coryphaena hippurus from the SE Gulf of California was evaluated. The bioaccumulation patterns of As were the same in the two species. In I. platypterus, As levels (mg kg^-1, wet weight) were gonads (7.4 ± 1.1) > liver (3.1 ± 0.1) > kidney (2.7 ± 0.1) > muscle (1.6 ± 0.1); in C. hippurus, As (mg kg^-1) levels were gonads (4.3 ± 0.6) > liver (3.2 ± 0.2) > kidney (2.3 ± 0.1) > muscle (1.2 ± 0.1). Differences in As distribution could be attributed to the biological functions of tissues. The hypothesis was confirmed that biomagnification was evidenced by the fact that As levels were lower in prey species than in predators. Intake of muscle from either fish did not represent a risk to humans if recommended portions a week are not exceeded, adults as much as 1802.4 g and 2454.1 g and children 257.5 and 350.6 g, for sailfish and dolphinfish, respectively. In addition, the likelihood of developing cancer due to consumption of edible tissues from either of these top predators was in the acceptable range (6.4 × 10^-5 to 27.3 × 10^-6 for a population that consumes 50 g of muscle in a week) but if a conservative combined slope factor is used the probabilities to develop bladder and lung cancer increments from 1.1 × 10^-3 to 9.1 × 10^-5.

Protecting water birds of wetlands: Using toxicological tests and ecological risk assessment, based on metal/loid (s) of water, sediment and biota samples

Water, sediment and biota (two fish and one shrimp species) samples were collected from rivers, ponds, mudflat and estuaries within the Mai Po Ramsar site in Hong Kong, China, to determine the concentrations of heavy metals/loid (HMs): cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), zinc (Zn), and arsenic (As). The mutagenicity and toxicity of water and sediment samples were evaluated using Ames test and Microtox® bioassay, respectively. Ecological risk assessments on water birds were also conducted based on HM concentrations in biota, sediment and water samples. In general, results showed that downstream of Shan Pui River and Ng Tung River had relatively higher HM concentrations (e.g. Cu: 0.992-9.49 μg/L; As: 0.342-5.83 μg/L) when compared with estuaries (Cu: 0.400-3.69 μg/L; As: 0.220-0.931 μg/L) and ponds (Cu: 0.0402-2.41 μg/L; As: 0.0501-2.10 μg/L), except Hg and Cd. On the other hand, sediment samples collected from Ng Tung River showed mutagenicity on Salmonella typhimurium tester strain TA100, while the mudflat samples had mutagenicity on tester strain TA98 used in the Ames tests. Microtox® bioassay indicated that only sediment of Ng Tung River showed acute toxicity with a 15 min half maximal effective concentration (EC₅₀) value of 30.5%. Results of ecological risk assessments showed that grey heron (Ardea cinerea), which feeds on fish and shrimps at Shan Pui River and ponds were not at risk. However, common sandpiper (Actitis hypoleucos), which feeds at ponds were subjected to a potential health risk due to its behavior of seeking food from the sediments, especially this bird species has a small body size. This indicates juvenile birds of other species may also be affected. Remediation should be implemented to relief the potential risk of Cu and Pb, to these water birds in the Mai Po Ramsar site.

Multiple exposure pathways of first-year university students to heavy metals in China: Serum sampling and atmospheric modeling

In this study, we collected 308 serum samples from 17 to 20 year old first-year university students who were recruited from Lanzhou University in China a few days after their enrollment to measure the serum Pb, Cd, Hg, and As levels, and specific questionnaires for age, sex, settlement and dietary structure were designed. A 3-D atmospheric transport model was used to simulate the atmospheric concentration and dry deposition across China based on gridded Pb emission inventory to examine the association between the spatial distribution of serum concentrations and environmental fates of Pb. The mean serum Pb, Cd, Hg, and As concentrations averaged over all participating young students were 21.38, 1.46, 3.86, and 4.69 μg/L, respectively. The Pb, Cd, and Hg levels in 3%, 7%, and 20% serum samples exceeded the standards. The minimum serum As and Hg concentrations and the maximum serum Pb and Cd concentrations occurred in urban areas. Seafood diet habits (P < 0.05), sex (P < 0.05), and relocation (P < 0.01) caused significant differences in serum As, Pb, and Cd concentrations. A cluster analysis was carried out to classify the exposure pathways for target contaminants. The results indicated that 4 heavy metals in the serum of volunteers from northern China could be grouped into the same category, in which significant positive correlations were found between the serum heavy metal levels and background concentrations of surface soil. However, in other provinces and metropolises, the atmospheric pollution level played a critical role involving in the inhalation exposure pathway. We demonstrated that serum Pb levels in freshman students were related to the atmospheric transport and dry deposition of Pb.

Trophodynamics of arsenic for different species in coastal regions of the Northwest Pacific Ocean: In situ evidence and a meta-analysis

China has been the major fishery producer in the Northwest Pacific Ocean for decades and the seafood safety deserves continuous concern. In this study, 188 organism and 27 sediment samples were collected from the Jiaozhou Bay, a typical semi-enclosed bay adjacent to the Northwest Pacific Ocean, to study the arsenic (As) pollution level and trophodynamics in the coastal regions of China combined with a meta-analysis. Results showed that arsenic was the most abundant in crustaceans with the average of 28.84 ± 4.95 mg/kg in dry weight, in comparison with molluscs (18.68 ± 2.51 mg/kg) and fish (9.31 ± 1.45 mg/kg). Additionally, based on a meta-analysis, arsenic in coastal organisms generally decreased from north to south in China. With increasing values of δ¹⁵N, arsenic was significantly biomagnified in the molluscs but bio-diluted in the groups of crustaceans and fish. When all the species were taken into consideration, overall bio-dilution of As was observed through the simplified food chain in the Jiaozhou Bay. Based on the target hazard quotient (THQ), the health risk of consuming seafood from the Jiaozhou Bay was not significant except for several kinds of crustaceans. The smaller THQs indicated lower health risk of eating molluscs and fish than crustaceans. Besides, urban households tended to undertake much higher risk than rural households. Based on our results, it is recommended for urban citizens to reduce the frequency of consuming crustaceans and give preference to fish when choosing seafood.

Elemental composition of aquaculture fish from West Bengal, India: nutrition versus food safety

Aquaculture production continues to grow in West Bengal, where on average people consume 8.2 kg capita^-1 of fish each year, and an extensive mosaic of aquaculture ponds has developed along the River Hugli as clay pits are repurposed. The adjacent brickworks and industry (especially tanneries) are a source of environmental pollution, with potential for bioaccumulation of potentially harmful elements (PHEs) in fish farmed in these ponds. Fish from aquaculture present an opportunity to meet food sufficiency in West Bengal; however, an investigation to assess their effectiveness for micronutrient supply balanced against food safety is required. Five ponds close to industrial brick manufacture (urban) and three from rural areas were assessed for the degree of pollution within their pond sediments and waters. Fish were also sampled from each location including a subset from the market in Kolkata to determine the concentrations of PHEs in their fish muscle tissue. Dietary intake and PHE loading were calculated for four fish species to evaluate their nutrient content with respect to recommended daily intakes for adults, e.g. calcium (Ca), potassium (K), magnesium (Mg), iron (Fe), zinc (Zn) and selenium (Se), and to establish whether the provisional maximum tolerable intakes (PMTIs) are exceeded for PHEs, e.g. aluminium (Al), arsenic (As), mercury (Hg), chromium (Cr), tin (Sn), copper (Cu) and lead (Pb). Preliminary results suggest that aquaculture is making an important contribution to nutrition, with fish being a good source of Se. However, in contrast to small wild-caught fish, aquaculture fish in the present study were poor sources of Fe, Ca and Zn. The fish also made substantial contributions (> 10%) to the PMTI of Hg and As. Therefore, there is an urgent need for ongoing monitoring and an expanded sampling programme, as well as research into approaches which might improve the nutritional quality of the farmed fish.

Health risk assessment of heavy metals in Cyprinus carpio (Cyprinidae) from the upper Mekong River

The purposes of this research are to quantify the concentration of heavy metals (Zn, Cu, As, Pb, Cd, and Hg) in the water and fish tissues of common carp (Cyprinus carpio) in the upper Mekong River and to thereby elucidate the potential dietary health risks from fish consumption of local residents. Surface water and fish tissues (gill, muscle, liver, and intestine) from four representative sample areas (influence by a cascade of four dams) along the river were analyzed for heavy metal concentrations. Results revealed that the levels of heavy metals in fish were tissue-dependent. The highest Cu and As levels were found in the liver; the highest Zn and Pb levels occurred in the intestine, and the highest Hg level was found in the muscle. The total target hazard quotient (THQ) value for residents is > 1 for long-term fish consumption, and local residents are, therefore, exposed to a significant health risk. Results from the current study provide an overall understanding of the spatial and tissue distribution of heavy metals in water and fish body along the upper Mekong River under the influence of cascade dams and highlight the potential health risk of As for the local residents of long-term fish consumption.

Aberrant methylation of FAT4 and SOX11 in peripheral blood leukocytes and their association with gastric cancer risk

Background: Aberrant DNA methylation, especially tumor suppressor gene hypermethylation, is a well-recognized biomarker of initial tumorogenesis stages. FAT4 and SOX11 are putative tumor suppressor genes and can be down-regulated by hypermethylation in various cancers tissues. However, in peripheral blood leukocytes, the association between these two genes methylation status, as well as the effects of gene-environment interactions, and gastric cancer (GC) risk remain unclear.

Methods: A hospital-based case-control study including 375 cases and 394 controls was conducted. Peripheral blood leukocytes DNA methylation status were detected by methylation-sensitive high-resolution melting (MS-HRM) assay. Logistic regression was adopted to analyze the relationship of FAT4 and SOX11 methylation with GC susceptibility.

Results: Positive methylation (Pm) and total positive methylation (Tpm) of FAT4 were significantly increased the risk of GC (OR = 2.204, 95% CI: 1.168-4.159, P = 0.015; OR = 1.583, 95% CI: 1.031-2.430, P = 0.036, respectively). Compared with controls, cases exhibited higher SOX11 Pm frequencies with OR of 2.530 (95% CI: 1.289-4.969, P = 0.007). Nonetheless, no statistically significant association between SOX11 Tpm and GC risk was observed. Additionally, interactions between FAT4 Tpm and increased consumption of freshwater fish (≥1 times/week) displayed an antagonistic effect on GC (OR = 0.328, 95% CI: 0.142-0.762, P = 0.009), and high salt intake interacted with SOX11 Tpm also showed statistically significant (OR = 0.490, 95% CI: 0.242-0.995, P = 0.048).

Conclusions:FAT4 aberrant methylation in peripheral blood leukocytes and gene-environment interactions were associated with the risk of GC, while SOX11 was controversial and needed to be more investigated.

Periphyton and abiotic factors influencing arsenic speciation in aquatic environments

Benthic periphytic biofilms are important food sources at the base of aquatic ecosystems. These biofilms also sit at the interface of oxic waters and hypoxic sediments, and can be influenced by or influence trace element speciation. In the present study, we compared arsenic (As) enrichment in periphyton exposed to arsenate (As[V]) or arsenite (As[III]) (20 μg/L, static renewal, 7 d), and we found similar accumulation patterns of total As (101 ± 27 and 88 ± 22 mg kg^-1 dry wt, respectively). Periphyton As was 6281- and 6684-fold higher than their aqueous exposures and occurred primarily as As(V). When these biofilms were fed to larval mayflies, similar total As tissue concentrations (13.9 and 14.6 mg kg^-1 dry wt, respectively) were observed, revealing significant biodilution (∼ 10% of their dietary concentrations). Finally, we investigated the influence of aeration and periphyton presence on As speciation in solutions and solid phases treated with As(III). Predominantly As(III) solutions were slowly oxidized over a 7-d time period, in the absence of periphyton, and aeration did not strongly affect oxidation rates. However, in the presence of periphyton, solution and solid-phase analyses (by microscale x-ray absorption spectroscopy) showed rapid As(III) oxidation to As(V) and an increasing proportion of organo-As forming over time. Thus periphyton plays several roles in As environmental behavior: 1) decreasing total dissolved As concentrations via abiotic and biotic accumulation, 2) rapidly oxidizing As(III) to As(V), 3) effluxing organo-As forms into solution, and 4) limiting trophic transfer to aquatic grazers. Environ Toxicol Chem 2018;37:903-913. © 2017 SETAC.

Distributions and contamination assessment of heavy metals in the surface sediments of western Laizhou Bay: Implications for the sources and influencing factors

Heavy metals (Cu, Pb, Cr, Cd and As) contents in surface sediments from western Laizhou Bay were analysed to evaluate the spatial distribution pattern and their contamination level. As was mainly concentrated in the coastal area near the estuaries and the other metals were mainly concentrated in the central part of the study area. The heavy metals were present at unpolluted levels overall evaluated by the sediment quality guidelines and geoaccumulation index. Principal component analysis suggest that Cu, Pb and Cd were mainly sourced from natural processes and As was mainly derived from anthropogenic inputs. Meanwhile, Cr originated from both natural processes and anthropogenic contributions. Tidal currents, sediments and human activities were important factors affecting the distribution of heavy metals. The heavy metal environment was divided into four subareas to provide a reference for understanding the distribution and pollution of heavy metals in the estuary-bay system.

Distribution of arsenic and other metals in crayfish tissues (Procambarus clarkii) under different production practices

Louisiana is one of the world's largest producer of crayfish. Arsenic (As) and other metals (Cd, Cu, Pb and Zn) concentrations were determined in crayfish tissues, plant and soil samples collected from Louisiana paddy rice fields, where crayfish/rice rotation farming is a common practice. The samples were collected from November 2013 to April 2014 from three different crayfish farming systems. Concentration of As in rice grain, rice straw, and native vegetation ranged between 0.33 and 0.41, 3.14-4.93, and 3.26-5.89mgkg^-1, respectively. The highest As levels in the crayfish external and internal body parts were found in gill (4.04±1.70mgkg^-1), followed by hepatopancreas (3.42±1.57mgkg^-1), exoskeleton (1.52±0.85mgkg^-1), and muscle (1.50±0.69mgkg^-1). Positive correlations between As levels in the crayfish muscle and the plant tissue on which they feed were found in all farming systems (r=0.405-0.438). The biomagnification factor (BMF) of As in different tissues varied between 0.29 and 1.08, having gill and hepatopancreas were the highest As accumulation while the lowest biomagnification was observed in crayfish muscle tissues which is a food source for human. The As levels along with other metals in crayfish muscle tissue were in acceptable levels for human consumption under all crayfish/rice rotation practices. Further studies are needed in determining the percentage of organic and inorganic arsenic in crayfish tissue.

Assessment of metal and bacterial contamination in cultivated fish and impact on human health for residents living in the Mekong Delta

Fish is the main source of animal protein and micronutrients for inhabitants in the lower Mekong River basin. Consumption of fish in the basin ranges from 41 to 51 kg capita(-1) year(-1). Thus, concerns of human health impacts caused by daily intake of metals contained in fish, and the incidence of bacterial contamination from Listeria and Escherichia coli have been raised. This study was conducted to 1) determine concentrations of metals, fecal indicator organisms, and Listeria spp. in cultivated common diet fish, and 2) assess human health risks as results of fish consumption on a daily basis. The results showed significant impacts of metal accumulation in fish especially from the intensive aquaculture. Chemical use to promote the rapid allometric growth of fish was expected to be the explanation for this finding. Concentrations of metals contained in different fish species were not statistically different with the exceptions of Na, Mn, and Zn. This might be due to the mobility of elements in aquaculture farms. Listeria and E. coli log CFU/g were 1.36 ± 0.11 (standard error) and 1.57 ± 0.1 s.e., respectively with higher counts observed in samples collected in market sites. Lastly, for human health risk assessment via fish consumption, it was found that hazard quotients of consuming As, Cu, and Zn contained in all fish species could contribute adverse health effects to the local residents (hazard quotients higher than 1). Therefore, risk management measures must be promoted and implemented in all study areas to reduce potential risks to local Vietnamese residents.

Life cycle exposure of the frog Silurana tropicalis to arsenate: Steroid- and thyroid hormone-related genes are differently altered throughout development

Arsenic contaminates water surface and groundwater worldwide. Several studies have suggested that arsenic acts as an endocrine disruptor in mammalian and non-mammalian species, although its chronic effect during development remains largely unknown. To address this question, life cycle exposures to 0, 0.3 and 0.8ppm of arsenate (pentavalent arsenic; As(V)) were performed in the Western clawed frog (Silurana tropicalis) from the gastrulae stage (developmental stage Nieuwkoop-Faber; NF12) until metamorphosis (NF66). Tissue samples were collected at the beginning of feeding (NF46; whole body), sexual development (NF56; liver), and at metamorphosis completion (NF66; liver and gonadal mesonephros complex). Real-time RT-PCR analysis quantified decreases in mRNA levels of genes related to estrogen- (estrogen receptor alpha and aromatase), androgen- (androgen receptor and steroid 5-alpha-reductase type 2), and cholesterol metabolism- (steroidogenic acute regulatory protein) at stage NF46. Similarly, arsenate decreased steroid 5-alpha-reductase type 2 expression in stage NF56 livers, but transcript increases were observed for both estrogen receptor alpha and steroidogenic acute regulatory protein at this stage. Given the changes observed in the expression of genes essential for proper sexual development, gonadal histological analysis was carried out in stage NF66 animals. Arsenate treatments did not alter sex ratio or produce testicular oocytes. On the other hand, arsenate interfered with thyroid hormone-related transcripts at NF66. Specifically, thyroid hormone receptor beta and deiodinase type 2 mRNA levels were significantly reduced after arsenate treatment in the gonadal mesonephros complex. This reduction in thyroid hormone-related gene expression, however, was not accompanied by any morphological changes measured. In summary, environmentally relevant concentrations of As(V) altered steroidogenesis-, sex steroid signaling- and thyroid hormone-related gene expression, although transcriptional changes varied among tissues and developmental stages.

Bioaccumulation Dynamics of Arsenate at the Base of Aquatic Food Webs

Periphyton is an important food source at the base of freshwater ecosystems that tends to bioconcentrate trace elements making them trophically available. The potential for arsenic-a trace element of particular concern due to its widespread occurrence, toxicity, and carcinogenicity-to bioconcentrate in periphyton and thus be available to benthic grazers is less well characterized. To better understand arsenate bioaccumulation dynamics in lotic food webs, we used a radiotracer approach to characterize accumulation in periphyton and subsequent trophic transfer to benthic grazers. Periphyton bioconcentrated As between 3,200-9,700-fold (dry weight) over 8 days without reaching steady state, suggesting that periphyton is a major sink for arsenate. However, As-enriched periphyton as a food source for the mayfly Neocloeon triangulifer resulted in negligible As accumulation in a full lifecycle exposure. Additional studies estimate dietary assimilation efficiency in several primary consumers ranging from 22% in the mayfly N. triangulifer to 75% in the mayfly Isonychia sp. X-ray fluorescence mapping revealed that As was predominantly associated with iron oxides in periphyton. We speculate that As adsorption to Fe in periphyton may play a role in reducing dietary bioavailability. Together, these results suggest that trophic movement of As in lotic food webs is relatively low, though species differences in bioaccumulation patterns are important.

Occurrence of perchloroethylene in surface water and fish in a river ecosystem affected by groundwater contamination

Long-term monitoring of the content of perchloroethylene (PCE) in a river ecosystem affected by groundwater contamination was performed at a site in the Czech Republic. The quality of surface water was monitored quarterly between 1994 and 2013, and fish were collected from the affected ecosystem to analyse the content of PCE in their tissue in 1998, 2011 and 2012. Concentrations of PCE (9-140 μg/kg) in the tissue of fish collected from the contaminated part of the river were elevated compared to the part of the river unaffected by the contamination (ND to 5 μg/kg PCE). The quality of surface water has improved as a result of groundwater remediation during the evaluated period. Before the remedial action, PCE concentrations ranged from 30 to 95 μg/L (1994-1997). Following commencement of remedial activities in September 1997, a decrease in the content of PCE in the surface water to 7.3 μg/L (1998) and further to 1 μg/L (2011) and 1.1 μg/L (2012) led to a progressive decrease in the average concentration of PCE in the fish muscle tissue from 79 μg/kg (1998) to 24 (2011) and 30 μg/kg (2012), respectively. It was determined that the bioconcentration of PCE does not have a linear dependence because the decrease in contamination in the fish muscle tissue is not directly proportional to the decrease in contamination in the river water. The observed average bioconcentration factors were 24 and 28 for the lower concentrations of PCE and 11 for the higher concentrations of PCE in the river. In terms of age, length and weight of the collected fish, weight had the greatest significance for bioconcentration, followed by the length, with age being evaluated as a less significant factor.

The associations between metals/metalloids concentrations in blood plasma of Hong Kong residents and their seafood diet, smoking habit, body mass index and age

The concentrations of metals/metalloids in blood plasma collected from 111 healthy residents (51 female, 60 male) in Hong Kong (obtained from the Hong Kong Red Cross Blood Transfusion Service, from March to April 2008) were quantified by means of a double-focusing sector field inductively coupled plasma optical emission spectrometer (ICP-OES). Results showed that concentrations of these toxic metals such as Hg, Cd, and Pb in Hong Kong residents were not serious when compared with other countries. Males accumulated significantly higher (p < 0.05 or 0.01) Fe (female 0.92 mg/L; male 1.28), Sn (0.44 μg/L; 0.60), Cr (0.77; 0.90), Hg (1.01; 1.73), and Pb (23.4; 31.6) than females. Smokers accumulated significantly higher (p < 0.05) Cd (smoker 0.27 μg/L; nonsmoker 0.17) and Pb (32.8; 17.6) than nonsmokers. Positive correlations were found between concentrations of As, Cd, Pb, and Hg, with respect to seafood diet habit, body mass index (BMI), and age. More intensive studies involving more samples are needed before a more definite conclusion can be drawn, especially on the causal relationships between concentrations of metals/metalloids with dietary preference and lifestyle of the general public.

Intake of freshwater fish and associated fatty acids and risk of breast cancer

To investigate the association between intake of freshwater fish and their fatty acids and the risk of breast cancer in Chinese women, we conducted a case-control study with 669 cases and 682 population-based controls in Jiangsu Province of China. A structured questionnaire was used to elicit detailed information. Unconditional logistic regression analysis was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Total freshwater fish intake was linked to decrease in the adjusted OR for breast cancer, but without dose-dependence. Analyses by freshwater fish species showed that consumption of black carp and silver carp was inversely related to breast cancer risk, with adjusted-ORs for the highest intake category of black carp (≥500g/month) of 0.54 (95%CI=0.33-0.92; P trend<0.002) and for silver carp (≥1000g/month) of 0.19 (95%CI=0.11-0.33; P trend<0.001). In contrast, consumption of crucian carp was positively related to breast cancer risk, with an adjusted OR for the highest intake category (≥1000g/month) of 6.09 (95%CI=3.04-12.2; P trend<0.001). Moderate intakes of SFA, PUFA, n3-PUFA and n6-PUFA from freshwater fish may decrease the risk of breast cancer among premenopausal women. The findings of this study suggest that intake of freshwater fish and their fatty acids may modify risk of breast cancer, and that different species of freshwater fish could have a different actions on breast cancer risk. Future epidemiologic studies are needed to know the effects of freshwater fish intake on breast cancer risk and the cause of these effects.