Water quality and fish size affect toxicity of endosulfan, an organochlorine pesticide, to rainbow trout

The acute toxicity of endosulfan in juvenile rainbow trout (Oncorhynchus mykiss, 10.61+/-1.69 g) was evaluated in glass aquaria under static conditions. Nominal concentrations of endosulfan in the toxicity test ranged from 1.3 microg l(-1) to 29 microg l(-1). The concentrations of endosulfan that killed 50% of the rainbow trout within 24-h (24-h LC50), 48-h LC50, 72-h LC50, and 96-h LC50 were 19.78, 8.89, 5.28, and 1.75 microg l(-1), respectively. None of the unexposed control fish died, and the first fish died 4 h after exposure to 26.3 microg l(-1) of endosulfan. Survival of fish was significantly increased with increasing fish size and decreased with decreased fish size at the same temperature (p<0.001). Temperature also had a significant effect on survival of fish. Alkalinity at levels above 20 mg l(-1) as CaCO3 significantly increased survival of fish at 19.78 microg l(-1) of endosulfan. Increasing alkalinity from 20 mg l(-1) as CaCO3 to 42 or higher concentrations tested in this study (121 mg l(-1) as CaCO3) significantly increased survival of fish (p<0.01). Total hardness ranging from 55 mg l(-1) as CaCO3 to 126 mg l(-1) as CaCO3 did not affect survival of fish exposed to endosulfan. Endosulfan toxicity was found to be irreversible when fish were exposed to minimum concentrations of endosulfan tested. Histologically, fish gills had lamellar edema, separation of epithelium from lamellae, lamellar fusion, and swelling of the epithelial cells. Melanomacrophage centers were scattered throughout the trunk kidney, head kidney, and spleen. The liver of endosulfan-exposed fish had severe focal necrosis. None of these lesions were seen in unexposed control fish. Results indicate that alkalinity, temperature, and fish size affect endosulfan toxicity of rainbow trout.     

Acute and Chronic Toxicity of Chlorine Dioxide (ClO2) and Chlorite (ClO2ˉ) to Rainbow Trout (Oncorhynchus mykiss) (4 pp)

Goal, Scope and Background Chlorite (ClO2ˉ) is a primary decomposition product when chlorine dioxide (ClO2) is added during water treatment; therefore the toxic effects of both compounds on aquatic organisms are possible. Limited data are available concerning their toxicity to fish. The aim of this study was to investigate sensitivity of rainbow trout to acute and chronic toxicity of chlorine dioxide and chlorite, and to estimate the Maximum-Acceptable-Toxicant-Concentration (MATC) of those compounds in fish. Methods The acute and chronic toxicity of chlorine dioxide and chlorite to larval and adult rainbow trout was investigated in 96-hour to 20-day laboratory exposures evaluating the wide range spectrum of biological indices under semi-static conditions. Results and Discussion Median lethal concentration (96-hour LC50) values derived from the tests were: 2.2 mg/l for larvae; 8.3 mg/l for adult fish and 20-day LC50 for larvae was 1.6 mg/l of chlorine dioxide, respectively. Chlorite was found to be from 48 to 18 times less acutely toxic to larvae and adult fish, correspondingly. Both chemical compounds induced similar toxic effects in rainbow trout larvae during chronic tests (they affected cardio-respiratory and growth parameters), but chlorine dioxide had a higher toxic potency than chlorite. A significant decrease in the heart rate and respiration frequency of larvae was established. However, within an increase in exposure duration recovery of cardio-respiratory responses was seen to have occurred in larvae exposed to chlorite. Meanwhile, in larvae exposed to chlorine dioxide, a significant decrease in cardio-respiratory responses remained during all 20-day chronic bioassays. Chlorine dioxide also more strongly affected growth parameters of rainbow trout larvae at much lower test concentrations. Decreased rate of yolk-sack resorption occurred only in the tests with chlorine dioxide. Conclusions Maximum-Acceptable-Toxicant-Concentration (MATC) of 0.21 mg/l for chlorine dioxide and of 3.3 mg/l for chlorite to fish was derived from chronic tests based on the most sensitive parameter of rainbow trout larvae (growth rate). According to substance toxicity classification accepted for Lithuanian inland waters, chlorine dioxide and chlorite can be referred to substances of \moderate\ toxicity to fish. Recommendations and Outlook Due to its very reactive nature, chlorine dioxide is rapidly (in a few hours) reduced to chlorite, which is persistent also as a biocide but 16 times less toxic to fish, according to MATC. Therefore, it is much more likely that fish will be exposed to chlorite than to chlorine dioxide in natural waters. Presently accepted, the Maximum-Permitted-Concentration of total residual chlorine (TRC) in waste-water discharging into receiving waters is 0.6 mg/l. If this requirement will not be exceeded, it is unlikely that fish would be exposed to lethal or even to sublethal concentrations of chlorine dioxide or chlorite. Furthermore, chlorine dioxide does not generate toxic nitrogenous (chloramines) or carcinogenic organic residuals (trihalomethanes). All these properties make chlorine dioxide a more promising biocide than chlorine.     

Feeding trial on rainbow trout: comparison of dry fish feed and Baltic herring as a source of PCDD/Fs and PCBs

Fish is an important source of dietary intake of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs). To assess bioaccumulation of PCDD/Fs and PCBs in farm-raised fish, rainbow trout were fed with either Baltic herring or dry fish feed. Baltic herring feed had a PCDD/F sum concentration of 125 ng kg(-1) dry weight (d.w.), and dry fish feed contained 18.2 ng kg(-1) d.w. of PCDD/Fs. The PCB concentrations of Baltic herring and dry fish feed were 188 and 48.7 microg kg(-1) d.w., respectively. After feeding with Baltic herring for 4 months, the PCDD/F concentration of the rainbow trout fillet was 27.3 ng kg(-1) fresh weight (f.w.), which was 7.0-fold higher than the initial concentration. The PCDD/F concentration and congener profile in rainbow trout had become almost the same as in Baltic herring. PCDD/Fs were accumulated in the fillet with an efficiency of 21%. Feeding of rainbow trout with dry fish feed resulted in a PCDD/F concentration of 8.08 ng kg(-1) f.w., denoting a 2.1-fold increase from the initial level. The accumulation efficiency was 29%. Time trends in PCB concentrations followed those of PCDD/Fs. After 4 months, the PCB sum concentration in herring-fed rainbow trout was 94.4 pg kg(-1) f.w., whereas in dry fish feed-fed rainbow trout it was 38.6 microg kg(-1) f.w. Accumulation efficiencies of PCBs were higher than those of PCDD/Fs. Based on the accumulated PCDD/F and PCB concentrations, it was estimated that frequent consumption of rainbow trout fed with Baltic herring could lead to a human daily intake that exceeds the recommendation of WHO.     

Toxic effects of orimulsion on rainbow trout <Emphasis Type="Italic">oncorhynchus mykiss</Emphasis>

GOAL, SCOPE AND BACKGROUND: Orimulsion (stable emulsion of natural bitumen and water) is a new imported industrial fuel in Lithuania. No data on its toxicity to fish is freely available. The aim of this study was to investigate sensitivity of rainbow trout (Oncorhynchus mykiss) to acute and chronic toxicity of orimulsion and to estimate the Maximum Acceptable Toxicant Concentration (MATC) of orimulsion to fish. METHODS: Laboratory tests were conducted on rainbow trout in all stages of development (embryos, larvae, adults). Acute toxicity (96-hour duration) and long-term (28 or 60-day duration) tests evaluating the wide range spectrum of biological indices were performed under semi-static conditions. RESULTS AND DISCUSSION: Median lethal concentration (96-hour LC50) values and their 95% confidence intervals derived from the tests were: 0.1 (0.09-0.12) to embryos, 0.06 (0.05-0.07) to larvae and 2.22 (2.02-2.43) to adult fish, and 28-day LC50 to adult fish was found to be 0.26 (0.21-0.32) g/l of total orimulsion respectively. The acute toxicity of orimulsion to rainbow trout can be characterised by a narrow zone of toxic effect and a sharp boundary between lethal and sublethal concentrations. The lowest 'safe' or 'no-effect' concentration values of total orimulsion obtained in long-term tests were equal to 0.09 g/l to adult fish, 0.019 g/l to embryos, and 0.0017 g/l to larvae. Proposed value of 'application factor' for orimulsion was found to be equal to 0.03. Since orimulsion has the property to disperse in all water volume, its toxic effect on fish can be characterised by the combined effects of dispersion and water-soluble-fraction. CONCLUSIONS: Maximum Acceptable Toxicant Concentration (MATC) of 0.0017 g/l of total orimulsion to fish was derived from long-term tests based on the most sensitive parameter of rainbow trout larvae (relative mass increase at the end of the test). According to substance toxicity classification accepted for Lithuanian inland waters, orimulsion can be referred to substances of 'moderate' toxicity to fish. RECOMMENDATIONS AND OUTLOOK: For prediction and evaluation of toxic impact of orimulsion accident spills on fish, some recommendations should be given. Since orimulsion has the property to disperse in all water volume during short time periods, the amounts of both spilled orimulsion and polluted water should be ascertained. Once both parameters are known, the real concentration of orimulsion in the water body must be determined. Then this concentration must be compared with 'safe' concentration to fish. By use of 'application factor' 0.03, approximate MATC for other fish species can be estimated when only acute toxicity data (96-hour LC50 value) is available.     

Polybrominated diphenyl ethers in whitefish from Swiss lakes and farmed rainbow trout

A method for trace analysis of polybrominated diphenyl ethers (PBDE) in fish based on gas chromatography/electron ionization high resolution mass spectrometry (GC/EI-HRMS) was developed, and levels of PBDE were determined in whitefish (Coregonus sp.) from eight Swiss lakes and in rainbow trout (Oncorhynchus mykiss) from four Swiss fish farms. PBDE concentrations (sum of PBDE congeners BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, and BDE-183) in filet from whitefish between 36 and 165 ng/g lipid weight (lw) were found, corresponding to wet weight (ww) concentrations of 1.6-7.4 ng/gww. PBDE contents in filet from farmed rainbow trout were significantly lower than in wild whitefish (12-24 ng/glw, 0.74-1.3 ng/gww), and the PBDE congener patterns were different for both species (a higher BDE-47 to BDE-99 ratio for farmed rainbow trout compared to wild whitefish was found). Whitefish PBDE levels [ng/glw] correlate better with the surface/volume ratio of the respective lakes (r(2)=0.70) than with other lake properties such as catchment area (size or number of inhabitants) or residence time, suggesting atmospheric deposition as an input pathway for PBDE. Based on an average daily consumption of 20 g whitefish (Switzerland) with a PBDE content of 7.4 ng/gww (highest PBDE concentration detected in this study), a maximum daily intake of 0.15 microg PBDE was estimated (0.026 microg/day for farmed trout). This number corresponds to the lower end of the estimate for the total PBDE intake of the Nordic consumer of 0.2-0.7 microg/day.     

Mercury in fish from the Pinchi Lake Region, British Columbia, Canada

Water, surface sediments, and <40 cm rainbow trout (Oncorhynchus mykiss) and northern pikeminnow (Ptychocheilus oregonensis) were collected from Pinchi Lake, British Columbia, and from several nearby reference lakes. Hg concentrations in sediment samples from Pinchi L. were highly elevated compared to sediments from reference lakes, especially in sites adjacent to and downstream of a former Hg mine. In both fish species examined, Hg concentration was positively related to age and/or fork length. In northern pikeminnow, Hg concentrations were also positively related to trophic level (deltaN). Hg concentrations in both fish species were highest in Pinchi L., and were higher in pikeminnow than in rainbow trout of similar size. Average Hg concentrations in small rainbow trout from all lakes, including Pinchi L., were lower than dietary levels reported to cause reproductive impairment in common loons (Gavia immer); however, Hg levels in small pikeminnow from Pinchi L. were sufficiently high to be of concern. The risk for Hg toxicity in the study area is greatest for animals that consume larger piscivorous fish such as larger northern pikeminnow or lake trout, which are known from previous studies to contain higher Hg concentrations.     

Effects of lead on the growth and delta-aminolevulinic acid dehydratase activity of juvenile rainbow trout, Oncorhynchus mykiss

Activity of delta-aminolevulinic acid dehydratase (ALA-D) in blood and organs is a biomarker of lead (Pb) contamination in fish. Because current methods cannot measure the bioavailability of Pb, this biomarker may predict exposure more accurately than analysis of Pb concentrations in water. Juvenile fish are generally more sensitive to Pb than adult fish, but due to their small size, analysis of ALA-D in blood and individual organs is difficult. By modifying the erythrocyte ALA-D procedure, we developed a method to measure ALA-D activity on the supernatant from the tissue homogenate of whole fish (juvenile rainbow trout, Oncorhynchus mykiss). Significant decreases in the activity of ALA-D in rainbow trout were observed after a 29-day exposure to 121 and 201 microg Pb liter(-1), but not after exposure to 29 or 48 microg Pb liter(-1). Pb also significantly reduced growth in fish exposed to 201 microg Pb liter(-1).     

Post-fire surface water quality: comparison of fire retardant versus wildfire-related effects

An understanding of the environmental effects of the use of wildland fire retardant is needed to provide informed decision-making regarding forest management. We compiled data from all post-fire surface water monitoring programs where the fire retardant constituents ammonia, phosphorus, and cyanide were measured, and data were available in the public domain. For streams near four major wildfires, we evaluated whether these chemicals originated primarily from fire or from retardant use. We compared measured concentrations in streams where chemical wildland fire retardant was applied with concentrations in streams draining areas where retardant was not used. Correlations with calcium provided an additional line of evidence, because calcium concentrations in ash are much higher than in retardant. Ammonia, phosphorus, and total cyanide were found in streams in burned areas where retardant was not used, at concentrations similar to those found in areas where retardant was applied. Concentrations of weak acid dissociable cyanide were generally non-detected or very low, whether or not wildland fire retardant was used in the watershed. These results indicate that the application of wildland fire retardant had minimal effects on proximate surface water quality. Cyanide concentrations in post-fire stormwater runoff were not affected by the presence of ferrocyanide in the retardant formulas and were due to pyrogenic sources.     

Toxicity of cobalt-complexed cyanide to <Emphasis Type="Italic">Oncorhynchus mykiss,Daphnia magna</Emphasis>, and <Emphasis Type="Italic">Ceriodaphnia dubia</Emphasis>

Background Cobalt cyanide complexes often result when ore is treated with cyanide solutions to extract gold and other metals. These have recently been discovered in low but significant concentrations in effluents from gold leach operations. This study was conducted to determine the potential toxicity of cobalt-cyanide complexes to freshwater organisms and the extent to which ultraviolet radiation (UV) potentiates this toxicity. Tests were also conducted to determine if humic acids or if adaptation to UV influenced sensitivity to the cyanide complexes. Methods Rainbow trout (Oncorhynchus mykiss), Daphnia magna, and Ceriodaphnia dubia were exposed to potassium hexacyanocobaltate in the presence and absence of UV radiation, in the presence and absence of humic acids. Cyano-cobalt exposures were also conducted with C. dubia from cultures adapted to elevated UV. Results With an LC50 concentration of 0.38 mg/L, cyanocobalt was over a 1000 times more toxic to rainbow trout in the presence of UV at a low, environmentally relevant irradiance level (4 μW/cm² as UVB) than exposure to this compound in the absence of UV with an LC50 of 112.9 mg/L. Toxicity was immediately apparent, with mortality occurring within an hour of the onset of exposure at the highest concentration. Fish were unaffected by exposure to UV alone. Weak-acid dissociable cyanide concentrations were observed in irradiated aqueous solutions of cyanocobaltate within hours of UV exposure and persisted in the presence of UV for at least 96 hours, whereas negligible concentrations were observed in the absence of UV. The presence of humic acids significantly diminished cyanocobalt toxicity to D. magna and reduced mortality from UV exposure. Humic acids did not significantly influence survival among C. dubia. C. dubia from UV-adapted populations were less sensitive to metallocyanide compounds than organisms from unadapted populations. Conclusions The results indicate that metallocyanide complexes may pose a hazard to aquatic life through photochemically induced processes. Factors that decrease UV exposure such as dissolved organic carbon or increased pigmentation would diminish toxicity.     

Comparison of in vitro and in vivo acute fish toxicity in relation to toxicant mode of action

Acute toxicity to fish hepatoma cell line PLHC-1 and to juvenile rainbow trout was examined for 18 plant protection products. The main objective was to explore whether hepatoma cells could be used to predict acute toxicity in fish taking into account the mode of toxic action and compound properties. Acute fish toxicity was determined using the OECD guideline test 203 and compared to predicted baseline LC50 of acute fish toxicity calculated with a quantitative structure-activity relationship (QSAR) derived for guppy fish. Cytotoxicity was determined through the inhibition of neutral red uptake (NR(50)) into lysosomes and compared to predicted baseline cytotoxicity derived for goldfish GFS cells. In general, NR50 values were higher by a factor ranging from 3 to 3000 than the corresponding acute LC50. A weak correlation between NR50 and LC50 values was found (log/log: r2=0.62). Also the lipophilicity (log K(ow)) was not a good predictor for cytotoxicity (r2=0.43) and lethality (r2=0.57) of these pesticides. The neutral red assay is detecting general baseline toxicity only. Comparing LC50 data to QSAR results, the compounds can be classified to act as narcotics or reactive compounds with a specific mode of toxic action in fish. The results indicate that limitation of the neutral red assay in predicting acute fish toxicity. A promising alternative might be the assessment of toxicity in a set of in vitro systems addressing also cell-specific functions which are related to the mode of toxic action of the compound.     

Effects of chlorpyrifos on reproductive performances of guppy (Poecilia reticulata)

Guppy (Poecilia reticulata) was selected to investigate the effects of chlorpyrifos on reproductive performances. Male and female guppy with proven fertility were selected from our own colony and the groups of fish (n=72/group) were exposed to pre-determined chlorpyrifos concentrations (0.002 microg/l, 2 microg/l) based on the 96-h LC50 for guppy. Mating behavior of males was recorded on the 2nd day of exposure. Offspring were counted and survival recorded on the 14th day. Gonopodial thrusts (8/15 min) in 0.002 microg/l and (4/15 min) in 2 microg/l were significantly different from the control group (11/15 min). Similarly, live birth reduced significantly to 8/female in 2 microg/l compared to 27/female in the control group. Survival of offspring after 14 days was reduced to 47% in the 2 microg/l group compared to 94% of survival in the control. Our findings demonstrate that low soluble concentrations of chlorpyrifos affect mating behavior, number of offspring and offspring survival of guppy.     

Waterborne and sediment toxicity of fluoxetine to select organisms

Ecological risk assessments of pharmaceuticals are currently difficult because little-to-no aquatic hazard and exposure information exists in the peer-reviewed literature for most therapeutics. Recently several studies have identified fluoxetine, a widely prescribed antidepressant, in municipal effluents. To evaluate the potential aquatic toxicity of fluoxetine, single species laboratory toxicity tests were performed to assess hazard to aquatic biota. Average LC(50) values for Ceriodaphnia dubia, Daphnia magna, and Pimephales promelas were 0.756 (234 microg/l), 2.65 (820 microg/l), and 2.28 microM (705 microg/l), respectively. Pseudokirchneriella subcapitata growth and C. dubia fecundity were decreased by 0.044 (14 microg/l) and 0.72 microM (223 microg/l) fluoxetine treatments, respectively. Oryias latipes survival was not affected by fluoxteine exposure up to a concentration of 28.9 microM (8.9 mg/l). An LC(50) of 15.2 mg/kg was estimated for Chironomus tentans. Hyalella azteca survival was not affected up to 43 mg/kg fluoxetine sediment exposure. Growth lowest observed effect concentrations for C. tentans and H. azteca were 1.3 and 5.6 mg/kg, respectively. Our findings indicate that lowest measured fluoxetine effect levels are an order of magnitude higher than highest reported municipal effluent concentrations.     

Mitigation of azinphos-methyl in a vegetated stream: comparison of runoff- and spray-drift

The effectiveness of aquatic macrophytes in reducing runoff- and spray-drift-induced azinphos-methyl (AZP) input was compared in a vegetated stream. Water, sediment and plant samples were taken at increasing distances from a point of input during a spray-drift event and two runoff (10 and 22 mm/day) events. Peak concentrations of AZP decreased significantly (R2=0.99; p<0.0001; n=5) from 0.24 microg/l to 0.11 microg/l during the 10mm runoff event. No reduction took place during the 22 mm event. AZP concentrations were reduced by 90% following spray-drift input, with peak concentrations decreasing significantly (R2=0.93; p=0.0084; n=5) from 4.3 microg/l to 1.7 microg/l with increasing distance from the point of input. Plant samples taken after the spray-drift event showed increased AZP concentrations in comparison to before the event indicating sorption of the pesticide to the macrophytes. Although peak concentrations of AZP were as effectively mitigated during the 10mm runoff event as during the spray-drift event, predictive modelling revealed that maximum concentrations expected during a worst-case scenario 10mm runoff event (0 days after application) are an order of magnitude lower than what can be expected for a worst-case spray-drift and 22 mm runoff event, suggesting that spray-drift-derived pesticide concentrations are more effectively mitigated than those of runoff.     

Preliminary investigation on the environmental occurrence and effects of antibiotics used in aquaculture in Italy

A preliminary investigation has been carried out on the occurrence and effects of antibiotics used in Italian aquaculture with the objective of identifying priorities for monitoring programmes. According to the information available on the most pertinent and diffuse fish diseases and their related therapies, the presence of flumequine and oxytetracycline in sediments sampled from two trout farms and three sea-bass farms and in their surrounding environments was selected for an analytical investigation. The concentrations of oxytetracycline and flumequine varied up to a maximum of 246.3 and 578.8 microg/kg d.w., respectively. Flumequine was seen to have the highest toxicity in a bioluminescence assay with EC50 values varying within the range of 12-15 mg/l, while the EC50 values for oxytetracycline were within the range of 121-139 mg/l. The results of the present study indicate flumequine and oxytetracycline as priority chemicals to be monitored for possible environmental side effects of aquaculture in Italy. Apart from peak concentrations the chronic presence of flumequine and oxytetracycline in sediments both inside and outside farms should also be considered. In spite of the potential risks related to the use of antibiotics, the concentrations found in the sediments of the studied fish farms are significantly lower than those found in other areas.     

Effects of pH and feeding regime on methylmercury accumulation within aquatic microcosms

The effect of pH (pH 5, 6 or 7) on accumulation of radiolabelled methylmercury was examined using a laboratory microcosm system. Accumulation of labelled mercury at three trophic levels, primary consumers (Daphnia magna), secondary consumers (rainbow trout, Salmo gairdneri) and tertiary consumers (walleye, Stizostedion vitreum) was not significantly affected by pH. Our results are in direct contrast with field observations of elevated methylmercury concentrations in fish from low pH water and indicate that the elevated mercury residues observed in the field result from factors other than the direct effects of pH on accumulation of methylmercury by aquatic organisms. Both water and diet were important as sources of the labelled mercury which was accumulated by walleye. Walleye which were fed rainbow trout, that had accumulated labelled mercury from within the experimental microcosms, accumulated almost twice as much labelled mercury as walleye fed non-labelled prey, or walleye which were not fed. Walleye fed non-labelled rainbow trout accumulated slightly more labelled mercury than walleye which were not fed, presumably as a result of the higher metabolic rate of the fish which were fed.     

Investigation of acute toxicity of permethrin on guppies Poecilia reticulata

Permethrin, a synthetic pyrethroid pesticide and potential toxic pollutant contaminating aquatic ecosystems, was investigated in the present study for acute toxicity. Guppy fish (Poecilia reticulata) were selected for the bioassay experiments. The experiments were repeated 3 times and the 48-h LC(50) was determined for the guppies. The static test method of acute toxicity test was used. Water temperature was regulated at 20+/-1 degrees C. In addition, behavioral changes at each permethrin concentration were observed for the individual fish. Data obtained from the permethrin acute toxicity tests were evaluated using the probit analysis statistical method. The 48-h LC(50) value for guppy was estimated as 245.7 microg/l. Values in the range of 0.05-97.0 microg/l have been reported for various other fish species.     

Tissue distribution and effects on hepatic xenobiotic metabolising enzymes of 2,3,3',4,4'-pentachlorobiphenyl (PCB-105) in COD (Gadus morhua) and rainbow trout (Oncorhynchus mykiss)

2,3,3',4,4'-Pentachlorobiphenyl, PCB-105 (IUPAC no. 105) was orally administered twice with a 4-day interval between dosings (total dose 10 mg kg(-1) body weight) to gonadally immature cod and rainbow trout of both sexes. The fish were killed 9 and 17 days after the first treatment, and the effects of PCB-105 on hepatic xenobiotic metabolising enzymes were determined by examining the cytochrome-P450-dependent ethoxyresorufin-O-deethylase (EROD) and aldrin epoxidase activities, and the EROD-catalysing P450 1A1 protein by indirect enzyme-linked immunosorbent assay (ELISA). Glutathione S-transferase activity towards 1-chloro-2,4-dinitrobenzene was included. The hepatic levels of the compound were determined. In addition, the distribution patterns of radio-labelled PCB-105 were studied by whole-body autoradiography. In exposed rainbow trout EROD activity and P450 1A1 by enzyme linked immunosorbent assay (ELISA) were significant induced, while GST activity was significant reduced. Exposed cod did not show significantly different enzyme values from controls, but percentage fat in the liver was significantly reduced. The whole cod liver contained about 1000 times more PCB-105 than the corresponding trout liver, and on a fat-weight basis the PCB level was five to six times higher in cod liver than in the rainbow trout liver. The autoradiographical investigation revealed high concentrations of radiolabelled compound in the liver and the brain of cod, while in rainbow trout the radiolabel was mainly confined to extrahepatic fat depots. These results demonstrate that the mono-ortho chlorinated coplanar analogue, PCB-105, has a different distribution pattern in the two fish species and that the potential for induction of the hepatic xenobiotic metabolising enzyme system seems to be lower in the cod than in the rainbow trout.     

In vivo evaluation of three biomarkers in the mosquitofish (Gambusia yucatana) exposed to pesticides

In this study, the acute toxicity and the in vivo effects of commercial chlorpyrifos, carbofuran and glyphosate formulations on cholinesterase (ChE), glutathione S-transferase (GST) and lactate dehydrogenase (LDH) activities of the mosquitofish (Gambusia yucatana) were investigated. In a first phase of the study, head and muscle ChE were characterized with different substrates (acetylthiocholine iodide, s-butyrylthiocholine iodide and propionylthiocholine iodide) and the selective inhibitors eserine hemisulfate, 1,5-bis(4-allyldimethylammoniumphenyl)-pentan-3-one dibromide (BW284C51), and N,N'-diisopropylphosphorodiamic acid (iso-OMPA). The results obtained suggest that the enzyme present in both head and muscle of G. yucatana is mainly acetylcholinesterase (AChE). Acute toxicity was evaluated by exposing fish to several concentrations of single pesticides and of a mixture of chlorpyrifos/glyphosate. LC50 values were determined after 96 h of exposure, except in the case of carbofuran for which LC50 was calculated after 24 h since almost all the fish died within this period. LC50 values were 0.085 mg/l for chlorpyrifos, 17.79 mg/l for glyphosate, 0.636 mg/l for carbofuran and 0.011 mg/l for the chlorpyrifos/glyphosate mixture. A Toxic Unit approach was used to compare the toxicity of chlorpyrifos and glyphosate when occurring in a mixture with their toxicities as single compounds. Synergistic effects of chlorpyrifos and glyphosate when present in a mixture were found. At the end of each bioassay (24 h for carbofuran, 96 for the other substances/mixture), effects on biomarkers were analyzed. Muscle LDH activity was not altered by any of the three pesticides tested. Gill GST activity was significantly inhibited (40%) by carbofuran after 24 h of exposure to concentrations equal or higher than 0.06 mg/l. ChE muscle and head activity were significantly inhibited (50% and 30%, respectively) by carbofuran at concentrations equal or higher than 0.25 mg/l. Chlorpyrifos induced a significant inhibition of both muscle and head ChE (80% and 50%, respectively) after 96 h of exposure to concentrations equal or higher than 0.05 mg/l. Carbofuran did not induce significant alterations of fish ChE. The ChE EC50 determined for chlorpyrifos/glyphosate mixture (0.070 mg/l) was higher than the correspondent value calculated for chlorpyrifos alone (0.011 mg/l) suggesting an antagonistic effect of glyphosate on ChE inhibition by chlorpyrifos. ChE activity of G. yucatana seems to be a good biomarker to diagnose the exposure of wild populations of this species exposed to anticholinesterase pesticides.     

MTBE and aromatic hydrocarbons in North Carolina stormwater runoff

A total of 249 stormwater samples were collected from 46 different sampling locations in North Carolina over an approximate 1-year period and analyzed to identify land use types where fuel oxygenates and aromatic hydrocarbons may be present in higher concentrations and at greater frequency. Samples were analyzed by gas chromatography-mass spectrometry in ion selective mode to achieve a quantitation limit of 0.05 microg/l. m-,p-Xylene and toluene were detected in over half of all samples analyzed, followed by MTBE: o-xylene: 1,3,5-trimethylbenzene: ethylbenzene; and 1,2,4-trimethylbenzene. Benzene, DIPE, TAME and 1,2,3-trimethylbenzene were detected in < 10% of the samples analyzed. Median contaminant concentrations (when detected) varied from 0.07 microg/l for ethylbenzene to 0.11 microg/l for toluene. All of the locations with significantly higher contaminant concentrations were associated with direct runoff from a gas station or discharge of contaminated groundwater from a former leaking underground storage tank. For all of the aromatic hydrocarbons, the maximum observed contaminant concentrations were over an order of magnitude lower than current drinking water standards.     

Organo-chlorine pesticide (DDT and HCH) residues in the Taihu Lake Region and its movement in soil-water system I. Field survey of DDT and HCH residues in ecosystem of the region

The use of organo-chlorine (DDT and HCH) has been banned in China for 20 years. A field survey was carried out during 1999-2000 in the Taihu Lake Region. Organo-chlorine pesticide (OCP) residues in soil, water, fish and sediment samples were investigated. DDT was detected in 5 out of 10 samples with concentration ranging from 0.3 to 5.3 microg/kg in the surface (0-15 cm) layer, 6 out of 10 with 0.5 to 4.0 microg/kg in the subsoil layer (16-30 cm), and 4 of 10 with 0 to 2.7 microg/ kg in the deep soil layer (31-50 cm). Results for HCH residues in soil samples were similar to those of DDT. These results indicate that OCP residues in 0-50 cm profile had been leached out or degraded to safe level. In river water DDT was detected in 10 out of 13 samples ranging from 0.2 to 9.3 microg/l, with an average of 1.0 microg/l. While HCH was detected in 12 out of 13 samples ranging from 0.02 to 36.1 microg/l, with an average 5.6 microg/l. DDT residues in sediment ranged from 0.1 to 8.8 microg/kg, while HCH ranged from 0.3 to 66.5 microg/kg. DDT residues in fish body ranged from 3.7 to 23.5 microg/kg and HCH ranged from 3.7 to 132 microg/kg. These results demonstrate an accumulation through food chain (from soil-water-sediment-microbes-crop-fish-... etc.), also that HCH residues are generally more persistent than DDT residues. However, all these data are well below than the state warning standard limit.