Induction of Adipocyte Differentiation by Polybrominated Diphenyl Ethers (PBDEs) in 3T3-L1 Cells

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants that were extensively used in commercial products. PBDEs are ubiquitous environmental contaminants that are both lipophilic and bioaccumulative. Effects of PBDEs on adipogenesis were studied in the 3T3-L1 preadipocyte cell model in the presence and absence of a known adipogenic agent, dexamethasone (DEX). A PBDE mixture designed to mimic body burden of North Americans was tested, in addition to the technical mixture DE-71 and the individual congener BDE-47. The mixture, DE-71, and BDE-47 all induced adipocyte differentiation as assessed by markers for terminal differentiation [fatty acid binding protein 4 (aP2) and perilipin] and lipid accumulation. Characterization of the differentiation process in response to PBDEs indicated that adipogenesis induced by a minimally effective dose of DEX was enhanced by these PBDEs. Moreover, C/EBPα, PPARγ, and LXRα were induced late in the differentiation process. Taken together, these data indicate that adipocyte differentiation is induced by PBDEs; they act in the absence of glucocorticoid and enhance glucocorticoid-mediated adipogenesis.     

The Correlation between Polybrominated Diphenyl Ethers (PBDEs) and Thyroid Hormones in the General Population: A Meta-Analysis

ObjectiveCertain epidemiological studies have suggested exposure to polybrominated diphenyl ethers (PBDEs) affect the production and secretion of thyroid hormones (TH); however, conflicting results have been reported in different studies. There is not a convincing conclusion about this debate to date.ConclusionThe findings in our meta-analysis indicate the effects of PBDEs on thyroid function may mainly depend on PBDEs exposure and their levels found in serum. The relationship between PBDEs exposure and changes in thyroid function seem to fit an approximate u-shaped curve. These predictions await further verification, namely a prospective longitudinal study.     

Polybrominated Diphenyl Ethers (PBDEs) in PM2.5, PM10, TSP and Gas Phase in Office Environment in Shanghai,China: Occurrence and Human Exposure

To evaluate risk via inhalation exposure of polybrominated diphenyl ethers (PBDEs) in office environment, thirty-six pairs air samples including PM_2.5 (particles with aerodynamic diameter less than 2.5 μm), PM₁₀ (particles with aerodynamic diameter less than 10 μm), total suspended particles (TSP) with matching gas phase were collected in office environment in Shanghai, China. The average concentrations of PM_2.5, PM₁₀ and TSP were 20.4, 27.2 and 50.3 μg/m₃, respectively. Σ₁₅PBDEs mean concentrations in PM_2.5, PM₁₀, TSP and gas phase were 51.8, 110.7, 148 and 59.6 pg/m³, respectively. Much more PBDEs distributed in fine fractions than coarse ones. PBDEs congener profiles found in PM_2.5, PM₁₀ and TSP (dominated by BDE-209) were different from that in gas phase (dominated by the tri- to penta-BDEs). Approximately 3.20 pg/kg/d PM_2.5 bound PBDEs can be inhaled into the lung; 3.62 pg/kg/d PM₁₀-PM_2.5(particles with aerodynamic diameter of 2.5-10 μm) bound PBDEs tended to be deposited in the upper part of respiratory system, and the intake of PBDEs via gas-phase was 2.74 pg/kg/d. The exposure of PBDEs was far below the minimal risk levels (MRLs), indicating lower risk from PBDEs via inhalation in the studied office in Shanghai.     

Reductive Debromination of Polybrominated Diphenyl Ethers by Anaerobic Bacteria from Soils and Sediments

Polybrominated diphenyl ethers (PBDEs) have attracted attention recently due to their proven adverse effects on animals and their increasing concentrations in various environmental media and biota. To gain insight into the fate of PBDEs, microcosms established with soils and sediments from 28 locations were investigated to determine their debromination potential with an octa-brominated diphenyl ether (octa-BDE) mixture consisting of hexa- to nona-BDEs. Debromination occurred in microcosms containing samples from 20 of the 28 locations when they were spiked with octa-BDE dissolved in the solvent trichloroethene (TCE), which is a potential cosubstrate for stimulating PBDE debromination, and in microcosms containing samples from 11 of the 28 locations when they were spiked with octa-BDE dissolved in nonane. Debromination products ranging from hexa- to mono-BDEs were generated within 2 months. Notably, the toxic tetra-BDEs accounted for 50% of the total product. In sediment-free culture C-N-7* amended with the octa-BDE mixture and nonane (containing 45 nM nona-BDE, 181 nM octa-BDEs, 294 nM hepta-BDE, and 19 nM hexa-BDE) there was extensive debromination of the parent compounds, which produced hexa-BDE (56 nM), penta-BDEs (124 nM), and tetra-BDEs (150 nM) within 42 days, possibly by a metabolic process. A 16S rRNA gene-based analysis revealed that Dehalococcoides species were present in 11 of 14 active microcosms. However, unknown debrominating species in some of the microcosms debrominated the octa-BDE mixture in the absence of other added halogenated electron acceptors (such as TCE). These findings provide information that is useful for assessing microbial reductive debromination of higher brominated PBDEs to less-brominated congeners, a possible source of the more toxic congeners (e.g., penta- and tetra-BDEs) detected in the environment.Since they were first developed in the 1960s, polybrominated diphenyl ethers (PBDEs) have been used as flame retardant additives in an array of common household and industrial appliances. As a result of their widespread use, PBDEs have become ubiquitous environmental contaminants, and increasing levels have been detected in the air, soil, and water (5, 12). In a recent study, Leung et al. reported the highest PBDE concentrations in soil samples (2.7 to ∼4.3 ppb) and combusted residues (33.0 to ∼97.4 ppb) that were collected in Guiyu, Guangdong Province, China (18). More worrisome is the fact that increasing concentrations of PBDEs have also been detected in marine mammals, birds, fishes, and human tissues (3, 14, 20, 30), and 63 ppm of PBDEs in bird eggs is the highest level ever found in biota (23). The PBDE concentrations in both environmental samples and biota have been increasing exponentially, with a doubling time of 4 to 6 years (5, 12). Although the PBDEs comprise 209 different congeners designated 1 to 209, the PBDE congeners most often detected in biota (e.g., human tissues) include tetra-brominated diphenyl ether (tetra-BDE) (congener 47), penta-BDEs (congeners 99 and 100), and hexa-BDEs (congeners 153 and 154), which may have originated directly from a commercially available penta-BDE technical mixture or indirectly via breakdown of an octa- or deca-BDE technical mixture (10, 12). PBDEs began to receive worldwide scientific and public attention when a temporal study performed from 1972 to 1997 revealed increasing concentrations of PBDEs in Swedish human breast milk (19). Toxicological studies of rodents using a commercial penta-BDE mixture (including tetra-, penta- and hexa-BDEs) and congeners in a commercial octa-BDE mixture (such as hepta-BDE [congener 183] and octa-BDE [congener 203]) revealed developmental neurotoxicity, reproductive toxicity, liver toxicity, and disruption of thyroid hormone levels (24, 26, 29).To date, studies of PBDEs have focused mainly on detection of these compounds in the environment and their potential adverse health effects; only a few studies have reported microbial debromination of PBDEs (7, 10, 22, 25). Recently, He et al. demonstrated debromination of a technical octa-BDE mixture by pure isolates of Dehalococcoides species, which generated hepta- to di-BDEs after 6 months of incubation (10). Additionally, microbes belonging to the genera Dehalobacter and Desulfitobacterium were also found to be able to debrominate individual PBDE congeners present in commercial octa-BDE mixtures (10, 22). However, the debromination of PBDEs in both studies required the presence of a primary electron acceptor (e.g., chloroethenes or chlorophenols); in other words, debromination occurred cometabolically.In addition to debromination of PBDEs by pure cultures, a previous study demonstrated that in anaerobic sludge 5% of added deca-BDE (congener 209) was debrominated to nona- and octa-BDEs (total amount of product, 0.5 nmol) after 238 days of incubation (7). Moreover, another study showed that deca-BDE was debrominated to products ranging from nona-BDEs to hexa-BDEs in 3.5 years with anaerobic sediments as the inocula (25). These findings suggest that microbial reductive debromination of highly brominated congeners, such as deca-, nona-, octa-, and hepta-BDEs, may contribute to formation of less-brominated PBDEs in the environment, which are potentially more toxic (e.g., tetra- and penta-BDEs). Additionally, debromination of less-brominated PBDE congeners, such as di-BDE, to mono-BDE and diphenyl ether was demonstrated in a fixed-film plug flow biological reactor (21). Besides microbial debromination, highly brominated PBDEs were also found to be transformed to lower congeners via photodegradation or in vivo metabolism in aquatic and terrestrial animals (1, 16).This study was initiated to obtain information about the distribution of microorganisms capable of debrominating highly brominated PBDE congeners to more toxic daughter products or the final product diphenyl ether by assessing microcosm samples collected from various locations. Debromination of an octa-BDE mixture was evaluated in the presence of the potential energy-generating cosubstrate trichloroethene (TCE) (PBDEs dissolved in TCE) or in the presence of the relatively inert solvent nonane (PBDEs dissolved in nonane). The latter experiment provided, for the first time, information about the possible microbes living on the energy generated from the debromination of an octa-BDE mixture in the absence of any cosubstrate, such as TCE or another primer compound. Initial insights into the key debrominating microbes were obtained by using genus-specific 16S rRNA gene-based techniques.     

Quantification of Hydroxylated Polybrominated Diphenyl Ethers (OH-BDEs), Triclosan,and Related Compounds in Freshwater and Coastal Systems

Hydroxylated polybrominated diphenyl ethers (OH-BDEs) are a new class of contaminants of emerging concern, but the relative roles of natural and anthropogenic sources remain uncertain. Polybrominated diphenyl ethers (PBDEs) are used as brominated flame retardants, and they are a potential source of OH-BDEs via oxidative transformations. OH-BDEs are also natural products in marine systems. In this study, OH-BDEs were measured in water and sediment of freshwater and coastal systems along with the anthropogenic wastewater-marker compound triclosan and its photoproduct dioxin, 2,8-dichlorodibenzo-p-dioxin. The 6-OH-BDE 47 congener and its brominated dioxin (1,3,7-tribromodibenzo-p-dioxin) photoproduct were the only OH-BDE and brominated dioxin detected in surface sediments from San Francisco Bay, the anthropogenically impacted coastal site, where levels increased along a north-south gradient. Triclosan, 6-OH-BDE 47, 6-OH-BDE 90, 6-OH-BDE 99, and (only once) 6’-OH-BDE 100 were detected in two sediment cores from San Francisco Bay. The occurrence of 6-OH-BDE 47 and 1,3,7-tribromodibenzo-p-dioxin sediments in Point Reyes National Seashore, a marine system with limited anthropogenic impact, was generally lower than in San Francisco Bay surface sediments. OH-BDEs were not detected in freshwater lakes. The spatial and temporal trends of triclosan, 2,8-dichlorodibenzo-p-dioxin, OH-BDEs, and brominated dioxins observed in this study suggest that the dominant source of OH-BDEs in these systems is likely natural production, but their occurrence may be enhanced in San Francisco Bay by anthropogenic activities.     

Elevated Serum Polybrominated Diphenyl Ethers and Alteration of Thyroid Hormones in Children from Guiyu,China

Informal electronic waste (e-waste) recycling results in serious environmental pollution of polybrominated diphenyl ethers (PBDEs) and heavy metals. This study explored whether there is an association between PBDEs, heavy metal and key growth- and development-related hormones in children from Guiyu, an e-waste area in southern China. We quantified eight PBDE congeners using gas chromatographic mass spectrometry, lead and cadmium utilizing graphite furnace atomic absorption spectrometry, three thyroids with radioimmunoassay and two types of growth hormones by an enzyme-linked immune-sorbent assay (ELISA) in 162 children, 4 to 6 years old, from Guiyu. In blood, median total PBDE was 189.99 ng/g lipid. Lead and cadmium concentrations in blood averaged 14.53±4.85 µg dL⁻¹ and 0.77±0.35 µg L⁻¹, respectively. Spearman partial correlation analysis illustrated that lead was positively correlated with BDE153 and BDE183. Thyroid-stimulating hormone (TSH) was positively correlated with almost all PBDE congeners and negatively correlated with insulin-like growth factor binding protein-3 (IGFBP-3), whereas free triiodothyronine (FT3) and free thyroxine (FT4) were negatively correlated with BDE154. However, no correlation between the hormones and blood lead or cadmium levels was found in this study. Adjusted multiple linear regression analysis showed that total PBDEs was negatively associated with FT3 and positively associated with TSH. Notably, FT4 was positively correlated with FT3, house functions as a workshop, and father''s work involved in e-waste recycling and negatively correlated with vitamin consumptions. TSH was negatively related with FT4, paternal residence time in Guiyu, working hours of mother, and child bean products intake. IGFBP-3 was positively correlated with IGF-1 and house close to an e-waste dump. These results suggest that elevated PBDEs and heavy metals related to e-waste in Guiyu may be important risk factors for hormone alterations in children.     

Probabilistic Estimation of Regional Dietary Exposure to Dioxins in Fish in Japan on the Basis of Market and Fish Distribution Network Data

Dietary consumption of fish is the greatest contributor to dioxin exposure of the general population in Japan. Unlike with other routes of exposure to dioxins, exposure via foodstuffs does not necessarily occur from local sources. Clarifying the distribution of fish from the catch area to local markets helps to control dioxin exposure from the head of the distribution chain down. We analyzed the data from 30 major central wholesale fish markets to determine both the market share of fish by catch area and the market share of major fish types in fish consumption markets. Probabilistic estimation of dietary exposure of the general population to dioxins in fish was conducted in seven regions in Japan. Probabilistic density functions (PDFs) were assigned to express the variability of data from monitoring of dioxin levels in fish by catch area or by fish type. From histograms of dioxin levels in fish by catch area, the mean and 5th to 95th percentile range of dietary exposure to dioxins in the region with the largest 95th percentile value were estimated, respectively, as 55.5 and 12.9–172.9 pg-TEQ/day. No statistically significant differences in dietary exposure to dioxins in fish were observed among the seven regions. Some specific coastal catch areas and some types of fish that had a greater impact than others on exposure were pinpointed for each region.     

Further Observations on Cryptobia dahli (Mastigophorea: Kinetoplastida) Parasitizing Marine Fish

Studies were conducted primarily to ascertain the mode of transmission of Cryptobia dahli parasitizing the digestive tract of lumpfish ( Cyclopterus lumpus ). Another flagellate, morphologically similar to C. dahli , was also observed in the gut of a deepsea fish ( Macrourus berglax ). Several invertebrates, which are food for lumpfish, were examined for flagellates, but were neither infected nor showed evidence of cystic stages. Parasites were more abundant in the stomach, especially at about pH 5, than in other areas of the digestive tract. Transmission was achieved by pipetting the parasites into the stomach of uninfected fish, by feeding food contaminated with flagellates, and also by holding infected and uninfected fish in the same aquarium. In nature, lumpfish probably acquire parasites during winter when they aggregate and regurgitate into seawater because parasites can survive for short periods outside their host.     

Environmental Effects of Marine Fish Pond Culture in the Ria Formosa (Southern Portugal)

Macrobenthic organisms, sediment and water characteristics were analysed in two fish farms in the Ria Formosa at control sites, near the outflows and inside the decantation ponds, in winter and summer 2001. Both farms operate under semi-intensive and intensive regimes. Statistical analysis reveals a very localised effect of fish farms near the outflow of the semi-intensive ponds, with an increase of density of small-sized organisms. The fish farms released high concentrations of nutrients and relatively low quantities of suspended solids. The effects of the effluents on the sediment were significant in the immediate vicinity of discharge point-source. The effects were localized mainly because all farms operate near the sea inlets, where water renewal rates are higher to ensure good fish production, thus permitting a important flushing of waste water. The effects of the effluents were more pronounced in summer because of the farms’ higher productivity at that time of the year. The decantation ponds, obligatory for the intensive regime, were apparently efficient in removing part of the solid waste. However, semi-intensive fish farms represent important sources of dissolved nutrients in the Ria Formosa and the joint effect of several fish farms in a semi-enclosed coastal system may be considerable.     

Detection of R+ Bacteria in Cultured Marine Fish,Yellowtails (Seriola quinqueradiata)

Many drug-resistant gram-negative bacilli were isolated from the intestinal tracts of yellowtails (Seriola quinqueradiata) cultured on farms in various parts of Kochi and Ehime Prefectures, Shikoku Island. They were Vibrio, Pseudomonas, Proteus, Citrobacter and some unidentified Enterobacteriaceae. Of these drug-resistant strains, Vibrio and Pseudomonas were found to carry R factors in high frequencies. These R factors had four types of resistance markers, SA, SA. CM, SM. CM. ABP. and SA. SM. CM. TC. All R factors were found to belong to the fi^– type. In contrast, only one drug-resistant gram-negative bacillus was detected in a cultured yellowtail on farms near Numazu City, Shizuoka Prefecture.     

Photolysis of Low-Brominated Diphenyl Ethers and Their Reactive Oxygen Species-Related Reaction Mechanisms in an Aqueous System

To date, no report was concerned with participation of reactive oxygen species in waters during photolysis of low-brominated diphenyl ethers (LBDEs). Herein, we found that electron spin resonance (ESR) signals rapidly increased with increasing irradiation time in the solution of LBDEs and 4-oxo-TMP solutions. But this phenomenon did not occur in the presence of NaN₃ (¹O₂ quencher) demonstrating generation of ¹O₂ in process of LBDEs photolysis. The indirect photolytic contribution rate for BDE-47 and BDE-28 was 18.8% and 17.3% via ¹O₂, and 4.9% and 6.6% via ·OH, respectively. Both D₂O and NaN₃ experiments proved that the indirect photolysis of LBDEs was primarily attributable to ¹O₂. The bimolecular reaction rate constants of ¹O₂ with BDE-47 and BDE-28 were 3.12 and 3.64 × 10⁶ M^-1 s^-1, respectively. The rate constants for BDE-47 and BDE-28 (9.01 and 17.52 × 10⁻³ min^-1), added to isopropyl alcohol, were very close to those (9.65 and 18.42 × 10⁻³ min^-1) in water, proving the less indirect photolytic contribution of ·OH in water. This is the first comprehensive investigation examining the indirect photolysis of LBDEs in aqueous solution.     

Hair Mercury Concentrations of Lactating Mothers and Breastfed Infants in Iran (Fish Consumption and Mercury Exposure)

Coastal populations with high seafood consumption in the South Caspian Sea (Iran) have a significant exposure to dietary mercury. This study assesses the biomonitoring of mercury in mothers and breastfed infants in the South Caspian Sea. The mean of mercury concentration in the hair of 93 pairs of mothers and infants was obtained and was 3.55 and 1.89???g?g^?1, respectively. A statistically significant correlation (R?=?0.850, P?=?0.000) was seen between mercury concentration in the hair of mothers and infants. The results of this study indicate that hair mercury concentrations exceeded the USEPA reference dose of 1???g?g^?1 in 82.7?% of mothers and 61.2?% of infants. Also, 31?% of the mothers and 10.7?% of the infants had mercury concentrations more than the WHO ??threshold?? level (5???g?g^?1). The age and fish consumption of mothers were the factors that significantly affected the hair mercury concentration of mothers and infants. Number of dental amalgam fillings of mothers was the factor that only affected mercury in the hair of mothers. According to the results, we can conclude that the main determinant of mercury exposure was the intake of mercury through fish consumption of mothers.     

Dietary Exposure to Lead and Cadmium in Yugoslavia

Abstract

Lead exposure still represents a matter of health concern especially in Yugoslavia. To assess the exposure of normal urban population to lead and cadmium through food, a preliminary monitoring was performed on a small group of urban population. Lead, cadmium and some essential elements (calcium, zinc, iron, copper and manganese) were analysed in collected duplicate diet samples and compared to similar population in Sweden. We found that dietary exposure to lead and cadmium is similar to other countries although Yugoslav urban population is exposed to much higher concentrations of lead in air than in cities of developed countries, due to high lead in gasoline. However, daily intake of some essential elements was significantly lower.

Also populations living around lead smelters in various parts of Yugoslavia are still exposed to elevated environmental lead and cadmium levels. To assess the exposure of the population living in this area, a cumulative long-term exposure to lead was determined by measuring lead in deciduous teeth. Concentrations of lead and cadmium in vegetables, soil and meals from the same region were also analysed. Values obtained for lead and cadmium in food products grown in exposed and control area were found to be related to respective concentrations of these elements in soil as well as to the distance from the smelter. Meals prepared in this region show the same trend, revealing very high intake particularly of lead.

The influence of nutritional factors, i.e. dietary calcium on lead metabolism, was also studied. Blood lead concentration was determined in two groups of peasant women living in two regions with different dietary calcium intake. Lower blood lead values were found in the higher dietary calcium intake region.     

Dietary Exposure to Lead and Cadmium in Sweden

Abstract

A duplicate diet study on male and female pensioners in 1970–71 showed mean daily dietary lead intakes of 30 μg and 19 μg respectively. The corresponding cadmium intakes were 10.5μg and 12.9 μg. Analysis of duplicate diets collected during seven consecutive 24-hour periods from 15 women in Stockholm in 1988 showed a mean daily lead intake of 26 μg (range 13–40 μg). The corresponding cadmium intake was 8.5μg (range 5.7–14 μg). Analysis of faeces samples corresponding to the duplicate diets showed similar lead and cadmium contents (mean lead content 24 μg day^?1, range 10–41 μg day^?1; mean cadmium content 8.9 μg day^?1 range 5.5–12 μg day^?1). The median lead and cadmium concentrations in human milk collected in Uppsala were 2 μg kg^?1 and 0.1 mg kg^?1 respectively. The median weekly intakes of lead and cadmium by the breast-fed infants were calculated to be 2 μg kg^?1 body weight and 0.1 μg kg^?1 body weight. Analysis of seven daily diets, together representing the weekly diet of an adult Swedish male, showed a mean lead content of 26 μg (range 15–45 μg), and a mean cadmium content of 10 μg (range 7–15 μg). The mean daily intakes of lead and cadmium found by analysing market baskets prepared in 1987 were 17μg and 12μg respectively. Calculations based on food balance sheet data and levels of lead and cadmium in individual foods showed mean daily intakes of 30 μg lead and 14 μg cadmium per person.     

Dietary Exposure to Organochlorine Compounds in Tarragona Province (Catalonia,Spain): Health Risks

The human health risks due to the dietary exposure to organochlorine compounds (OC) were assessed in the Catalan stretch of the Ebro River (Spain). The concentrations of various persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), pentachlorobenzene (PeCB), various hexachlorocyclohexanes (HCHs), as well as dichloro-diphenyl-trichloroethane (DDT) and derivatives, were determined in samples of fish and seafood, vegetables, fruits, and rice, acquired in localities of the zone under evaluation. In general terms, pollutant concentrations were similar to recent levels reported in the literature. With the exception of the consumption of fish and seafood by children, and due to the presence of PCBs (Aroclor 1254), food intake from local sources does not pose non-carcinogenic risks for all population groups examined. The presence of OC in foods of local origin in the Catalan basin of the Ebro River would not increase the health risks for the area's consumers.     

Lipid and Fatty Acid Composition in the Flesh of an Edible Marine Fish: Amadi (Coilia reynaldi)

Amadi is a small sized edible marine fish species (Coilia reynaldi) under the order-Clupeiformes. It is important for principal lipids and in particular for highly unsaturated fatty acids which have potential biomedical benefits. Among the lipid classes, phospholipids were found to be the most predominant constituents than the glycolipid and neutral lipid in Amadi. Twenty six fatty acids were quantified by open tube gas–liquid chromatography. Dominant fatty acids in this fish are Palmitic acid (C_16:0), Stearic acid (C_18:0), Oleic acid (C_18:1n?9), Myristic acid (C_14:0), Palmitoleic acid (C_16:1), Docosahexanoic acid (C_22:6n?3), Pentadecanoic acid (C_15:0), and Eicosatetraenoic acid (C_20:4n?3). Fatty acid deficiency in fish species is indicated by the presence of C_20:3n?9 acid. It is absent in this fish.The content of DHA and EPA are maximum in amount in neutral lipid than other lipid classes.     

Fish mercury levels in relation to characteristics of hydroelectric reservoirs in Newfoundland, Canada

Mercury levels in fish have been demonstrated to increase after impoundment with augmented levels of mercury predicted to decline as the reservoir ages. Previous research in Newfoundland predicted return rates in the order of 10 to 12 years for landlocked Atlantic salmon or ouananiche (Salmo salar) and 7 years for brook trout (Salvelinus fontinalis). In order to test the validity of these predictions on a broader spatial and temporal scale, and develop more generally predictive models, mercury levels in three fish species were studied in 16 older Newfoundland hydroelectric reservoirs of various age (32 to 95 years) and area flooded (21 to 13,000 ha).Mercury concentrations were standardized to fish length and correlated with physical, chemical, and biological characteristics of the sampling sites. Standard length mercury levels ranged from 0.23 to 0.86 ppm in ouananiche, 0.13 to 0.59 ppm in brook trout, and 0.22 to 0.72 in arctic charr (Salvelinus alpinus). Fish in excess of the Canadian Safety Limit (0.5 ppm) were collected from 14 of 16 sites for ouananiche, 8 of 17 sites for brook trout, and 3 of 7 sites for arctic charr, including control lakes. Standard length fish mercury levels were correlated with reservoir age and (log₁₀) area flooded for ouananiche and with pH for arctic charr. A multiple regression model was developed relating standard length mercury in ouananiche with reservoir age and log₁₀ of the flooded area. There were no apparent relationship between reservoir characteristics and brook trout mercury concentrations. Based on this analysis, it is not possible, at present, to develop generally predictive models for all species found in Newfoundland impoundments.     

Isolation of Multidrug-Resistant Stenotrophomonas maltophilia from Cultured Yellowtail (Seriola quinqueradiata) from a Marine Fish Farm

Six strains of multidrug-resistant Stenotrophomonas maltophilia were isolated from cultured yellowtail. The strains were divided into two clusters based on the 16S rRNA genes, and all of them contained L1 metallo-β-lactamase and L2 β-lactamase genes. Differences in the intercluster divergence between the lactamase genes suggest that horizontal transfer of the genes occurred.