Teratogenesis,toxicity, and bioconcentration in frogs exposed to dieldrin

Teratogenesis, acute and chronic toxicity, growth and bioconcentration were investigated in various life stages (embryos, tadpoles, juveniles, adults) of the frogsXenopus laevis (African clawed frog),Rana catesbeiana (bullfrog) andRana pipiens (leopard frog) exposed to aqueous dieldrin in static-renewal and flow-through systems in a study on the development of wildlife-based water quality criteria.R. catesbeiana was the most sensitive tadpole in acute tests;X. laevis was the most sensitive in embryo-larval and chronic tadpole tests. Tadpole 96-h LC50s ranged from 40.4 to 49.5 g/L dieldrin forX. laevis, from 8.7 to 30.3 g/L forR. catesbeiana and was 71.3 g/L forR. pipiens. The 24-day LC50 forX. laevis tadpoles was 5.5 g/L dieldrin; the 28-day LC50 forR. pipiens tadpoles was 8.3 g/L. AdultR. pipiens had a 28-day LC50 of 53.4 g/L dieldrin. Gross spinal deformities in embryo-larval tests were observed at dieldrin concentrations as low as 1.3 g/L after 10-days exposure toX. laevis and at 25.4 g/L for a 21-day exposure toR. catesbeiana. MeanX. laevis 14 to 21-day LOAEL (Lowest Observed Adverse Effect Level) and NOAEL (No Observed Adverse Effect Level) values for embryo-larval tests (25.5 and 11.0 g/L dieldrin, respectively) were virtually the same as the 21-day single test values obtained forR. catesbeiana (25.1 and 11.0 g/L dieldrin). Mean 14 to 24-dayX. laevis LOAEL and NOAEL values for tadpole chronic tests (1.6 and <1.4 g/L dieldrin, respectively) were lower than the 28-day single test values obtained forR. pipiens (4.1 and 1.9 g/L, respectively).Tissue dieldrin levels at the LC50, LOAEL and NOAEL in the tadpole acute tests were fairly similar betweenX. laevis (11, 24 and 7 g/g, respectively) andR. catesbeiana (means of 8.6, 12.0 and 1.2 g/g, respectively). In the tadpole chronic tests, dieldrin tissue concentrations were even closer for these parameters forX. laevis (1.8, 1.5 and 0.8 g/g, respectively) andR. pipiens (1.7, 0.6 and 0.4 g/g, respectively). Mean steady-state bioconcentration factors (BCF) for tadpoles (whole body) ranged from 430 forX. laevis, and from 540 to 1,130 forR. pipiens. Mean steadystate BCFs for adultR. pipiens skin, muscle and liver ranged from 40 to 310. The relative similarity of response to dieldrin betweenX. laevis and the two ranid species in this study demonstrates its usefulness in assessing potential environmental hazards. The current dieldrin water quality criterion of 0.0019 g/L appears protective of frogs.     

Measuring bioconcentration factors in fish using exposure to multiple chemicals and internal benchmarking to correct for growth dilution

Modern chemical legislation requires measuring the bioconcentration factor (BCF) of large numbers of chemicals in fish. The BCF must be corrected for growth dilution, because fish growth rates vary between laboratories. Two hypotheses were tested: (1) that BCFs of multiple chemicals can be measured simultaneously in one experiment, and (2) that internal benchmarking using a conservative test substance in the chemical mixture can be used to correct for growth dilution. Bioconcentration experiments were conducted following major elements of the OECD 305 guideline. Fish were simultaneously exposed to 11 chemicals selected to cover a range of BCFs and susceptibility to biotransformation. A method was developed to calculate the growth-corrected elimination rate constant from the concentration ratio of the analyte and a benchmarking chemical for which growth dilution dominated other elimination mechanisms. This method was applied to the experimental data using hexachlorobenzene as the benchmarking chemical. The growth dilution correction lowered the apparent elimination rate constants by between 5% and a factor of four for eight chemicals, while for two chemicals the growth-corrected elimination rate constant was not significantly different from zero. The benchmarking method reduced the uncertainty in the elimination rate constant compared to the existing method for growth dilution correction. The BCFs from exposing fish to 10 chemicals at once were consistent with BCF values from single-chemical exposures from the literature, supporting hypothesis 1.     

Cadmium toxicity and bioconcentration in laregmouth bass and bluegill

Summary The exposure of juvenile largemouth and bluegill to cadmium (0.0005 to 0.85 mg/liter) resulted in accumulation of this metal in concentrations greater than those of the water. The quantity of metal accumulat d increased as the exposure concentration increased. An equilibrium developed between the concentrations of the metal in the water and in the tissues after approximately 2 months. Metal accumulations on the bass tissues were higher in the internal organs, followed by the gills and the remainder of the body.Bass were more sensitive to cadmium than the bluegill. Abnormal behavior patterns observed in both species suggested that the nervous system was the site of damage.     

Use of polynomial expressions to describe the bioconcentration of hydrophobic chemicals by fish

For the bioconcentration of hydrophobic chemicals by fish, relationships have been previously established between uptake rate constants (k1) and the octanol/water partition coefficient (Kow), and also between the clearance rate constant (k2) and Kow. These have been refined and extended on the basis of data for chlorinated hydrocarbons, and closely related compounds including polychlorinated dibenzodioxins, that covered a wider range of hydrophobicity (2.5 less than log Kow less than 9.5). This has allowed the development of new relationships between log Kow and various factors, including the bioconcentration factor (as log KB), equilibrium time (as log teq), and maximum biotic concentration (as log CB), which include extremely hydrophobic compounds previously not taken into account. The shape of the curves generated by these equations are in qualitative agreement with theoretical prediction and are described by polynomial expressions which are generally approximately linear over the more limited range of log Kow values used to develop previous relationships. The influences of factors such as hydrophobicity, aqueous solubility, molecular weight, lipid solubility, and also exposure time were considered. Decreasing lipid solubilities of extremely hydrophobic chemicals were found to result in increasing clearance rate constants, as well decreasing equilibrium times and bioconcentration factors.     

Regression approaches to derive generic and fish group-specific probability density functions of bioconcentration factors for metals

In the framework of environmental multimedia modeling studies dedicated to environmental and health risk assessments of chemicals, the bioconcentration factor (BCF) is a parameter commonly used, especially for fish. As for neutral lipophilic substances, it is assumed that BCF is independent of exposure levels of the substances. However, for metals some studies found the inverse relationship between BCF values and aquatic exposure concentrations for various aquatic species and metals, and also high variability in BCF data. To deal with the factors determining BCF for metals, we conducted regression analyses to evaluate the inverse relationships and introduce the concept of probability density function (PDF) for Cd, Cu, Zn, Pb, and As. In the present study, for building the regression model and derive the PDF of fish BCF, two statistical approaches are applied: ordinary regression analysis to estimate a regression model that does not consider the variation in data across different fish family groups; and hierarchical Bayesian regression analysis to estimate fish group-specific regression models. The results show that the BCF ranges and PDFs estimated for metals by both statistical approaches have less uncertainty than the variation of collected BCF data (the uncertainty is reduced by 9%-61%), and thus such PDFs proved to be useful to obtain accurate model predictions for environmental and health risk assessment concerning metals.     

Evaluation of various molecular parameters as predictors of bioconcentration in fish

A reliable set of data on the bioconcentration factors (KB) of a diverse range of compounds in fish was selected from the literature. Using the structures of these compounds, the following molecular parameters were calculated: molecular weight (MW), solvent accessible molecular surface area (SASA), solvent accessible molecular volume (SAV), molar refraction (MR), largest principal moment of inertia (LPMI) and several molecular connectivity indices of the Randi? type (1 chi, 2 chi, 3 chi, 1 chi vr, 3 chi c). The relationships between these parameters and log KB were evaluated for all compounds and the following subgroups: chlorinated hydrocarbons (CHC), polyaromatic hydrocarbons (PAH), and CHC and PAH combined. These relationships indicated that SASA, SAV, and MR were good predictors of log KB for the CHC and PAH combined or alone and the other parameters were less satisfactory with these groups. In addition with the CHC, the log of these parameters displayed an improved correlation with log KB due to apparent nonlinearity in the log to linear relationship. Thus, with these groups of compounds, calculated values of SASA, SAV, and MR provide a satisfactory means of estimating log KB without measured data.     

A review and comparison of models for predicting dynamic chemical bioconcentration in fish

Over the past 20 years, a variety of models have been developed to simulate the bioconcentration of hydrophobic organic chemicals by fish. These models differ not only in the processes they address but also in the way a given process is described. Processes described by these models include chemical diffusion through the gill's interlamellar water, epithelium, and lamellar blood plasma: advective chemical transport to and from the gill by ventilation and perfusion, respectively; and internal chemical deposition by thermodynamic partitioning to lipid and other organic phases. This article reviews the construction and associated assumptions of 10 of the most widely cited fish bioconcentration models. These models are then compared with respect to their ability to predict observed uptake and elimination rates using a common database for those model parameters that they have in common. Statistical analyses of observed and predicted exchange rates reveal that rates predicted by these models can be calibrated almost equally well to observed data. This fact is independent of how well any given model is able to predict observed exchange rates without calibration. The importance of gill exchange models and how they might by improved are also discussed.     

Field evaluation of triclopyr ester toxicity to fish

Two field experiments were conducted to assess the predictions of laboratory time-toxicity tests regarding lethal effects of triclopyr butoxyethyl ester (TBEE) on fish in standing and flowing water bodies. Large lake enclosures were treated with TBEE by backpack sprayer at concentrations of 0.25–7.6 mg/L, expressed as acid equivalents. Median dissipation times for TBEE in lake water ranged from 4–8 d.Effects of the treatments on survival and growth of caged rainbow trout were measured. All trout died by 3 d at initial concentrations of 0.69–7.6 mg/L. There was 43% mortality of rainbow trout in the enclosure treated at 0.45 mg/L, and no mortality in the 0.25 mg/L enclosure or the controls. The treatments at the two lower concentrations had significant adverse effects on the growth rates of surviving trout. TBEE was applied to sections of a forest headwater stream at nominal concentrations of 0.8 mg/L and 2.7 mg/L. These concentrations represent maximum-expected environmental concentrations in 50- and 15-cm deep bodies of water, respectively, when directly oversprayed at an application rate of 3.84 kg/ha. Concentrations of TBEE were rapidly dissipated (as much as 70% decline within 55 m) and exposure periods at concentrations above 0.1 mg/L varied from 25 min in the low-concentration area to 55 min in the high-concentration area. The applications of TBEE at both initial test concentrations did not result in any mortality of resident brook trout. There were no significant effects of the herbicide treatments on the growth of 1+ and 2+ brook trout, but there were indications that the growth of 0+ trout was reduced as a result of exposure to TBEE in the stream. These results were in general agreement with the predictions of laboratory time-toxicity tests.     

Chronic toxicity of chloroform to Japanese medaka fish

Japanese medaka (Oryzias latipes) were continually exposed in a flow-through diluter system for 9 months to measured chloroform concentrations of 0.017, 0.151, or 1.463 mg/L. Parameters evaluated were hepatocarcinogenicity, hepatocellular proliferation, hematology, and intrahepatic chloroform concentration. Histopathology was evaluated at 6 and 9 months. Chloroform was not hepatocarcinogenic to the medaka at the concentrations tested. Chronic toxicity was evidenced at these time points by statistically significant ([alpha] = 0.05) levels of gallbladder lesions and bile duct abnormalities in medaka treated with 1.463 mg/L chloroform. We assessed hepatocellular proliferation by exposing test fish to 5-bromo-2'-deoxyuridine in the aquarium water for 72 hr after 4 and 20 days of chloroform exposure; we then quantified area-labeling indices of the livers using computer-assisted image analysis. We observed no treatment-related increases in cellular proliferation. We analyzed cells in circulating blood in medaka after 6 months of chloroform exposure. Hematocrit, leukocrit, cell viability, and cell counts of treated fish were not significantly different from those of control fish. Using gas chromatography (GC), we evaluated intrahepatic concentrations of chloroform in fish after 9 months of exposure. Livers from the 0.151 and 1.463 mg/L chloroform-treated fish had detectable amounts of chloroform, but these levels were always lower than the aquaria concentrations of chloroform. Thus, it appeared that chloroform did not bioaccumulate in the liver. Unidentified presumptive metabolite peaks were found in the GC tracings of these fish livers.     

Assessment of an approach to estimating aquatic bioconcentration factors using reduced sampling

For a broad range of circumstances, we show that reliable bioconcentration factor (BCF) estimates can be made using a study design that is based on standard regulatory guideline test procedures but that uses significantly fewer animals and resources. This minimized design involves taking tissue samples only twice during a 14-d depuration period. The utility of the minimized test design was first assessed by resampling data from a series of standard guideline tests and calculating the BCF estimates that would have been obtained if the test had been performed using the minimized design. Data from 25 bioconcentration curves giving BCF estimates ranging from approximately 0.3 to over 20,000 were used. The correlation of log BCF estimates from the guideline study with log BCF estimates from the simulated minimized tests was r=0.99, and the slope of the regression line was 0.96. The robustness of BCF estimates to random variation in measurement of chemicals in fish and water (coefficients of variation of concentrations ranging up to 25%) was evaluated using Monte Carlo simulations. For chemicals with depuration half-lives of less than the length of the depuration period, median BCF estimates from the Monte Carlo simulations of the minimized design were always within 7% of the true BCE The ratio of the 95th to the 5th percentile BCF estimates was always less than or equal to 3.7. Furthermore, the span from the 95th to the 5th percentile of BCF estimates was only 15% wider in the minimized test than in the full guideline test, even though animal use and analytical effort was markedly reduced.     

Chemiobiokinetic study in freshwater fish exposed to lindane: Uptake and excretion phase rate constants and bioconcentration factors

Four species of freshwater fish (Brachidanio rerio, Poecilia reticulata, Salmo gairdneri, Lepomis macrochirus) were exposed to lindane (2–6 μg 1^‐1) in a flow‐through system to investigate chemical bioconcentration kinetics. Lindane concentration was assayed in fish fat and water matrices at different exposure and excretion times. For all species, it was observed that a concentration plateau in fish was already reached after a 60 h exposure, whereas > 90% of lindane apeared to have been excreted after a 160 h excretion period. Bioconcentration and its kinetics did not appear to be significantly species‐dependent. Bioconcentration factors were in the range of 300–730 in fish and from 20 to 50 times as high in fat.     

Acute toxicity of phosphate ester mixtures to invertebrates and fish

Summary The acute toxicity of three commercial phosphate ester mixtures (hydraulic fluids) was tested against two invertebrates and four fishes. Pydraul 50E was more toxic than Houghtosafe 1120 in static and flow-through tests; Pydraul 115E was the least toxic. In flow-through tests these phosphate esters were less acutely toxic than PCB's. However, sublethal reactions to the phosphates suggest a need for chronic toxicity studies.     

Acute toxicity of phosphate ester mixtures to invertebrates and fish

The acute toxicity of three commercial phosphate ester mixtures (hydraulic fluids) was tested against two invertebrates and four fishes. Pydraul 50E was more toxic than Houghtosafe 1120 in static and flow-through tests; Pydraul 115E was the least toxic. In flow-through tests these phosphate esters were less acutely toxic than PCB's. However, sublethal reactions to the phosphates suggest a need for chronic toxicity studies.