Morphological and Neurotoxicological Findings in Tropical Freshwater Fish (<Emphasis Type="Italic">Astyanax</Emphasis> sp.) After Waterborne and Acute Exposure to Water Soluble Fraction (WSF) of Crude Oil

The water-soluble fraction (WSF) of crude oil is a complex highly volatile and toxic mixture of hydrocarbon chains (polyaromatics, heterocyclics), phenols, and heterocyclic compounds containing nitrogen and sulfur. To evaluate the toxic effects of WSF in tropical freshwater teleosts and to develop methodologies that could investigate the toxic mechanisms of WSF in tropical organisms, an acute toxicity experiment was conducted with Astyanax sp. Three dilutions (15%, 33%, and 50%) of WSF obtained from Campos Bays crude oil (Brazil) were used to study morphological and biochemical responses of the fish. Prior to exposure, the distribution and rate of volatilization of the WSF into each aquarium for the same exposure period was quantified by spectrofluorimetry. Five individuals of Astyanax sp. were exposed to duplicate WSF of 0, 15, 33, and 50% for each of 12-, 24-, and 96-h exposures for a total of 120 individuals. Liver and gills were sampled from five fish from each treatment and were analyzed by histology, scanning and transmission electron microscopy. A fragment of muscle was also collected from each fish to measure acetylcholinesterase activity. Water analysis showed that only 4 h after dilution, an important loss of hydrocarbons in 33% and 50% of WSF was observed. In addition, 50% of hydrocarbon mass was lost in all tested dilutions after 24 h with significant difference for the 50% WSF at all measured times, demonstrating the high volatility of WSF in freshwater. Damage in the liver and the gills included the presence of necrosis, loss of hepatocytes limit, inflammation areas, cellular proliferation, aneurysms, and disorganization of the second lamellae. The 33% WSF significantly reduced acetylcholinesterase activity in fish. Our study demonstrated that the WSF of crude oil caused damage in organs and tissues of tropical freshwater Astyanax sp. and provided also the basis for a better understanding of the toxic mechanisms of WSF in freshwater fishes.     

Toxicity of biodiesel, diesel and biodiesel/diesel blends: comparative sub-lethal effects of water-soluble fractions to microalgae species

The water-soluble-fractions (WSF) from biodiesel and biodiesel/diesel blends were compared to diesel in their sub-lethal toxicity to microalgae. Chemical analyses of aromatics, non-aromatics hydrocarbons and methanol were carried out in the WSF, the former showing positive correlation with increasing diesel concentrations (B100 < B5 < B3 < B2 < D). Biodiesel interacted with the aqueous matrix, generating methanol, which showed lower toxicity than the diesel contaminants in blends. The WSF caused 50% culture growth inhibition (IC50-96 h) at concentrations varying from 2.3 to 85.6%, depending on the tested fuels and species. However, the same species sensitivity trend (S. costatum > N. oculata > T.chuii > P. subcapitata) was observed for all the tested fuels.     

Health effects of gasoline refueling vapors and measured exposures at service stations

Liquid gasoline is a complex mixture of at least 150 hydrocarbons with about 60-70% alkanes (paraffins), 25-30% aromatics, and 6-9% alkenes. In order to evaluate the potential for health effects from inhaling gasoline vapors, it is essential to understand the major differences in the composition of vapors versus liquid gasoline. The small chain, low carbon-numbered components are more volatile and thus in higher percentages in the vapor phase than the larger and heavier molecules. It is noteworthy that the concentrations of aromatics (the more toxic of the gasoline components), are depleted to about 2% in the vapor phase, with the light paraffins (the less toxic) enriched to about 90%. Actual measurements of vapor exposure at service stations confirm that the vapor composition is primarily to low weight alkanes although benzene is also emitted and represents the chemical of greatest concern. A perceived health concern from inhaling gasoline vapors is the potential for carcinogenicity based on the induction of kidney tumors in male rats and liver tumors in female mice exposed to wholly-vaporized gasoline. However, the results of the animal studies are of questionable relevance for human risk assessment due to the unique mechanism operative only in the male rat and since the exposure was to wholly-vaporized gasoline rather than the gasoline vapor mixture to which humans are exposed. Recent research supports the hypothesis that branched-chain-alkanes bind to a globulin specific to make rats, alpha 2-u-globulin. The protein complex can not be degraded in the usual manner so that protein accumulation occurs in renal cells, leading to cytotoxicity, death, proliferation, and with prolonged exposure, kidney cancer. The results of epidemiology studies fail to link an increase in cancer to exposure to gasoline vapors.     

Sediment toxicity tests using benthic marine microalgae Cylindrotheca closterium (Ehremberg) Lewin and Reimann (Bacillariophyceae)

A new method for sediment toxicity testing using marine benthic pennate noncolonial diatom (Cylindrotheca closterium, formerly Nitzschia closterium) has been developed. This microalgae showed a good growth rate during the experimental period, even when low enriched media were used. Sediment spiked with heavy metals [cadmium (Cd), copper (Cu), and lead (Pb)] was employed to determine the EC(50) values, using microalgal growth inhibition as the endpoint. The obtained results were as follows: Three heavy metals (Cd, Cu, and Pb), previously spiked on experimental sediment, were separately assayed in toxicity tests. The EC(50) values for these heavy metals in microalgal growth inhibition tests resulted to be 79 mg kg(-1) for Cd, 26 mg kg(-1) for Cu, and 29 mg kg(-1) for Pb (in experimental sediment). The influence of sediment granulometry on the growth of microalgal population was also studied, finding that the growth of the microalgal population on media containing sediment with a relation sand-size:silt size of 9:1 was not different from optimal growth (occurring in media containing 100% sand-sized sediment). The diatom C. closterium proved to be a suitable organism for sediment toxicity tests, due to its sensitivity and fast growth even in poorly enriched media.     

Effects of exposure to the water-soluble fraction of crude oil on the swimming performance and the metabolic and ionic recovery postexercise in Pacific herring (Clupea pallasi)

The swimming performance and recovery from exercise were determined in juvenile Pacific herring (Clupea pallasi) following exposure to the water-soluble fraction (WSF) of North Slope crude oil for more than eight weeks. Total polycyclic aromatic hydrocarbon concentrations (mean +/- standard error) at the beginning of exposures were as follows: control, 0.2 +/- 0.1 microg/L; low, 9.6 +/- 2.5 microg/L; medium, 40.7 +/- 6.9 microg/L; and high, 120.2 +/- 11.4 microg/L. Biological availability of hydrocarbons was confirmed by a significant induction of hepatic cytochrome P450 content and ethoxyresorufin-O-deethylase activity. Critical swimming speed (Ucrit) was significantly reduced in fish exposed to the highest concentration of WSF for 96 h (11% +/- 3.7% reduction) and at the two highest concentrations at four weeks (16% +/- 3.6% and 29% +/- 5.4% reductions) and eight weeks (11% +/- 3.8% and 40% +/- 5.7% reductions). Mortality occurred in all groups 24 h following Ucrit swim trials, with significantly higher mortalities observed in fish exposed to WSF in a concentration- and time-dependent manner (maximum mortality of 72.2% +/- 5.5% in the eight-week, high-exposure group). Burst swimming alone resulted in increased plasma cortisol, lactate, Na+, and Cl- concentrations and decreased muscle glycogen levels that returned to baseline values by 24 h. An interpretation of the effect of WSF exposure on postexercise metabolic recovery was complicated by pre-exercise alterations in several parameters. The time courses and magnitudes of several key postexercise parameters, including plasma cortisol, lactate, and muscle glycogen, were significantly altered by exposure to WSE The present study clearly shows that hydrocarbon exposure can reduce the swimming ability of fish and their ability to recover from exhaustive exercise.     

Relative toxicity of technical material and commercial formulation of malathion and endosulfan to a freshwater fish, Channa punctatus (Bloch)

Relative toxicity of technical and commercial formulations of malathion and endosulfan were evaluated by determining LC50 values and their 95% confidence interval end points for 24, 48, 72, and 96 hr exposure to Channa punctatus using the "trimmed Spearman-Karber method." The commercial formulations of malathion and endosulfan were 1.176 and 1.88 times more toxic than their technical materials, respectively. Ninety-six-hour LC50 values (0% trimming) of technical and commercial formulations of malathion and endosulfan (95% confidence interval in parentheses) were 4.51 (4.11-4.96) and 3.89 (3.46-4.38) mg/liter, and 5.78 (4.49-7.44) and 3.07 (2.43-3.84) micrograms/liter, respectively. Fishes showed characteristic changes in behavior when exposed to various concentrations of these insecticides.     

含铅、无铅汽油尾气排出颗粒提取物的细胞膜毒性比较

[目的]通过实验室细胞染毒模型来揭示无铅汽油的使用能否减低汽车尾气颗粒有机提取物的细胞膜毒性。[方法]在发动机台架试验上，分别使用市售90#含铅及无铅两种汽油来制造尾气。收集尾气的颗粒物及其吸附有机物，并检测尾气中HC与C0浓度。将体外培养中国仓鼠肺细胞(CHL)暴露于尾气的提取物中，通过检测细胞培养液中乳酸脱氢酶（LDH)及细胞内K^ 及Ca^2 浓度来分析细胞内外物质交换的变化，从而说明不同汽油排出尾气颗粒有机提取物的细胞膜毒性。[结果]随着对细胞染毒剂量的增加，培养液中的LDH浓度以及细胞内的Ca^2 浓度有增加的趋势，而细胞内K^ 浓度有降低的趋势，这种变化呈剂量—反应关系。统计学检验表明，无铅汽油尾气颗粒提取物的细胞膜毒性与对照组及其他实验组有显著性的差别。[结论]无铅汽油的使用能减少尾气中C0、HC及颗粒物的排放。与含铅汽油相比较，无铅汽油的颗粒吸附有机物的细胞膜毒性有所降低。     

A new approach to regulating hydrocarbon emissions from technology operations with separated oil

Due to the fact that the approximate safe levels for hydrocarbons C1-C5 and C6-C10 have been excluded from their hygienic standards, it is proposed to regulate the emissions of contaminants from manufacturing operations with oil, by using the existing hygienic standards for petroleum oil, diluent naphtha, paint naphtha, kerosene, and hydrocarbons C12-C19 on the basis of oil fractional analysis according to GOST 2177-99.     

The identification and measurement of components in gasoline,kerosene, and no. 2 fuel oil that partition into the aqueous phase after mixing

Some of the most common spills in waterways involve petroleum products, which are complex mixtures of varying compositions, depending on source and refining procedures. The tendency for components of potential toxicological significance to distribute to the aqueous phase under spill conditions needs to be determined. This paper is devoted to the chemical analysis of the water-soluble fractions (WSF) of gasoline, kerosene, and No. 2 fuel oil, which were added to drinking water and extracted into the aqueous phase under simulated field conditions. Initial aspects of the study dealt with the identification and distribution of the major components to the aqueous phase using pentane extraction and capillary column gas chromatography/mass spectrometry (GC/MS) for analyses. Results show that at least 95% by weight of the components in the WSF of each fuel sample were aromatic compounds having 6 to 13 carbons.     

Gasoline vapor exposures. Part II. Evaluation of the nephrotoxicity of the major C4/C5 hydrocarbon components

Analysis of workplace exposures to gasoline vapors revealed that C4 and C5 hydrocarbons constitute anywhere from 67 to 74% by weight of a typical vapor. Furthermore, it was found that n-butane, isobutane, n-pentane, and isopentane together comprise greater than 90% of all the C4/C5 vapor components and approximately 61 to 67% by weight of the total vapor. Accordingly, a 21-day inhalation toxicity study of a blend consisting of 25% (w/w) each of these four hydrocarbons was conducted using rats to assess the potential for these major gasoline vapor components to induce kidney damage. No evidence of the kidney lesions typically associated with hydrocarbon-induced nephropathy was observed in rats exposed at up to 11 800 mg/m3 (4437 ppm) of the blend.     

Combined effects of algal (Chlorella vulgaris) density and ammonia concentration on the population dynamics of Ceriodaphnia dubia and Moina macrocopa (Cladocera)

Ammonia is a natural variable in ponds and lakes. Although an important source of nitrogen for microalgae, at high concentrations ammonia can affect the density and diversity of cladocerans. Using the cladocerans Ceriodaphnia dubia, and Moina macrocopa, the effect of nominal concentrations of ammonium chloride under acute and chronic exposures at different levels of algal food was tested. Regardless of food level, C. dubia was more sensitive than M. macrocopa to ammonia. In the absence of food, the median lethal concentration of ammonia (LC(50) 24 h) for C. dubia was (112 mg L(-1)) less than half that of M. macrocopa (232 mg L(-1)). When algal food (0.5 x 10(6) and 1.5 x 10(6) cells ml(-1) of Chlorella) was used, the LC(50) values were much higher for both cladoceran species. Based on the population growth studies, it was found that in controls of M. macrocopa an increase in the availability of Chlorella from 0.5 to 1.5 x 10(6) cells mL(-1) led to an increase in the maximum density from 4.7 +/- 0.2 to 16.4 +/- 1.2 ind.mL(-1), while in C. dubia the peak population density decreased from 7.9 +/- 0.6 to 5.0 +/- l.0 ind.mL(-1). An increase in ammonia concentration (10 to 40 mg L(-1) for C. dubia and 20 to 120 mg L(-1) for M. macrocopa) resulted in a corresponding decrease in peak population densities of the tested cladocerans. The rate of population increase (r) values for M. macrocopa in the controls ranged from 0.21 +/- 0.001 and 0.25 +/- 0.02 at 0.5 and 1.5 x 10(6) cells mL(-1) of Chlorella, respectively. The corresponding values of C. dubia in controls were 0.21 +/- 0.004 and 0.18 +/- 0.01. At 0.5 x 10(6) cells mL(-1) of algal food, the r values became negative under 40 and 120 mg L(-1) of ammonia for C. dubia and M. macrocopa, respectively. The role of algal food in ammonia toxicity to cladocerans was discussed. (c) 2002 Elsevier Science (USA).     

Comparative toxicity of tetra ethyl lead and lead oxide to earthworms,Eisenia fetida (Savigny)

Leaded gasoline contains tetra ethyl lead (TEL) as an antiknocking agent, which produces major amounts of lead oxide in automobile exhaust along with traces of TEL. To minimize the lead contamination, methyl tertiary butyl ether (MTBE) is used as a substitute for producing unleaded gasoline. It has become increasingly apparent that young children are highly susceptible to the harmful effects of lead. Hence, a study was carried out to monitor lead toxicity in soil, using adult earthworms (Eisenia fetida, Savigny). Leaded gasoline (TEL) and lead oxide are 383- and 211-fold more toxic than unleaded gasoline (MTBE) in 7 days of exposure and 627- and 290-fold more toxic in 14 days, respectively. Results indicate that the presence of TEL in leaded gasoline and lead oxide has a significant effect on behavior, morphology, and histopathology of earthworms. Absorption of TEL into the tissues is comparatively less than that of lead oxide but toxic effects were severe. Rupture of the cuticle, extrusion of coelomic fluid and inflexible metameric segmentation were observed, causing desensitization of the posterior region leading to fragmentation in earthworms.     

Toxicity,Uptake, and Release of the Water-Soluble Fraction of Crude Oil in Different Developing Stages of the Prawn <Emphasis Type="Italic">Macrobrachium borellii</Emphasis>

The effects of a water-soluble fraction of light crude oil dissolved in freshwater (WSF) on Macrobrachium borellii exposed at three life stages was evaluated. Adults, larvae (PL), and embryos were exposed to five levels of WSF for 96 h. At 48 and 72 h PL were significantly more sensitive to WSF than adults, though values for 96-h LC50 were not significantly different (1.56 and 1.41 mg/L, respectively). Mortality was never high enough to allow LC50 calculation in embryos, but chronic exposure to WSF increased the mortality near hatching and significantly decreased PL survival compared to the control group. The uptake, accumulation, and depuration of WSF were evaluated in adult prawns (lipid content 1.5% wet wt) exposed to a sublethal concentration for 96 h followed by a 10-d depuration period. Hydrocarbons were rapidly taken up, and after 24 h most of them reached an equilibrium concentration. Increases in the number and alkylation of the aromatic rings enhanced both their accumulation and their retention. When returned to clean freshwater, levels of lighter aromatics dropped rapidly over 12 h. From these studies we conclude that early life stages of M. borellii are not very vulnerable to WSF toxicity, while adults have a rapid uptake and release of most of the contaminating hydrocarbons, probably due to their low lipid levels.     

Absence of hydrocarbon-induced nephropathy in rats exposed subchronically to volatile hydrocarbon mixtures pertinent to gasoline

Ninety-day inhalation studies were conducted on 50:50 weight percent (wt %) mixtures of n-butane:n-pentane and isobutane:isopentane, respectively, and on a distillation cut boiling below 145 degrees F of a reference unleaded gasoline blend to assess the nephrotoxicity of these volatile mixtures. The mixtures of butanes and pentanes were selected because these four hydrocarbons are the most prevalent components of gasoline vapors encountered under typical occupational exposures. The 0-145 degrees F gasoline distillation fraction was tested because it reasonably approximates the composition of gasoline vapors measured under occupational settings. Male and female F-344 rats were exposed to 2 levels of each mixture, 6 hours per day, 5 days per week, for 13 weeks. The target concentrations for the butane:pentane mixtures were 4500 and 1000 parts per million (ppm), while 5200 and 1200 ppm were set for the gasoline distillation fraction. An interim sacrifice was conducted after 28 days. The rats were not significantly affected by the exposures, and there was no evidence of hydrocarbon-induced nephropathy in either sex at the termination of each study. However, at the 28-day interim sacrifice period for both butane:pentane mixtures, mild, transient treatment-related but not exposure-related kidney effects were observed in the male rats. These perturbations were absent at the interim sacrifice period for the gasoline distillation fraction.     

Responses of embryonic and larval inland silversides, Menidia beryllina, to a water-soluble fraction formed during biodegradation of artificially weathered Alaska North Slope crude oil

Weathered Alaska North Slope crude oil (ANS 521) was stirred for 2 and 14 days in 20 salinity sterile seawater or for 14 days in seawater with nutrients and a group of three (GO3) microorganisms from Prince William Sound, Alaska, that were capable of biodegrading hydrocarbons. A total of 0.65 and 0.69 mg/L water soluble fraction (WSF) of neutral fraction hydrocarbons was recovered from the 2- and 14-day stirred sterile systems, respectively. In comparison, a total of 7.5 mg/L WSF neutral fraction hydrocarbons was recovered from systems containing ANS 521 that were stirred and biodegraded by the GO3 microbes for 14 days. Toxicity/teratogenicity tests were conducted with neutral fraction hydrocarbons recovered from the sterile and biodegraded systems using embryonic inland silversides, Menidia beryllina. Hydrocarbons from the sterile systems did not cause statistically significant teratogenic responses at concentrations of 1%, 10%, and 100% (w/v) of recovered fractions (redissolved in 20 salinity sterile seawater). Counts of heart contraction rates were significantly lower (0.05) at the 100% WSF concentration of hydrocarbons on days 5 and 6 of embryogenesis. In contrast, recovered and redissolved neutral fraction hydrocarbons from ANS 521, that were biodegraded for 14 days, caused statistically significant (0.05) teratogenic responses at the 1, 10, and 100% WSF concentrations. Measurement of heart contraction rates showed statistically significant (0.05) reductions at the 100% WSF concentration on days 2 through 6 of embryogenesis, compared to controls.Contribution No. 934 from the Gulf Breeze Environmental Research Laboratory. Mention of trade names does not imply endorsement by the U.S. Environmental Protection Agency.     

Validation of the narcosis target lipid model for petroleum products: gasoline as a case study

The narcosis target lipid model (NTLM) was used to predict the toxicity of water-accommodated fractions (WAFs) of six gasoline blending streams to algae (Pseudokirchnereilla subcapitata, formerly Selenastrum capricornutum), juvenile rainbow trout (Oncorhynchus mykiss), and water flea (Daphnia magna). Gasolines are comprised of hydrocarbons that on dissolution into the aqueous phase are expected to act via narcosis. Aquatic toxicity data were obtained using a lethal-loading test in which WAFs were prepared using different gasoline loadings. The compositions of the gasolines were determined by analysis of C3 to C13 hydrocarbons grouped in classes of n-alkanes, iso-alkanes, aromatics, cyclic alkanes, and olefins. A model was developed to compute the concentrations of hydrocarbon blocks in WAFs based on gasoline composition and loading. The model accounts for the volume change of the gasoline, which varies depending on loading and volatilization loss. The predicted aqueous composition of WAFs compared favorably to measurements, and the predicted aqueous concentrations of WAFs were used in the NTLM to predict the aquatic toxicity of the gasolines. For each gasoline loading and species, total toxic units (TUs) were computed with an assumption of additivity. The acute toxicity of gasolines was predicted to within a factor of two for algae and daphnids. Predicted TUs overestimated toxicity to trout because of experimental factors that were not considered in the model. This analysis demonstrates the importance of aliphatic hydrocarbon loss to headspace during WAF preparation and the contribution of both aromatic and aliphatic hydrocarbons test to the toxicity of gasolines in closed systems and loss of aliphatics to headspace during WAF preparation. Model calculations indicate that satisfactory toxicity predictions can be achieved by describing gasoline composition using a limited number of aromatic and aliphatic hydrocarbon blocks with different octanol-water partition coefficients.     

Hydrocarbon nephropathy in male rats: identification of the nephrotoxic components of unleaded gasoline

Previous subchronic and/or chronic inhalation studies of unleaded gasoline and a variety of petroleum naphthas, solvents, and distillates have shown that these complex materials are capable of inducing a distinctive nephropathy which appears limited to male rats. Therefore a series of gavage screening studies using male F-344 rats was conducted on components of gasoline to more clearly identify the major contributors to this nephrotoxicity. The dosing regimen consisted of 20 doses administered once daily, 5 days per wk for 4 wk. Tested were 15 pure hydrocarbon compounds typically found in unleaded gasoline boiling range, 4 naphtha streams representative of those commonly used to blend gasolines and 3 distillation fractions covering the less volatile portions of gasoline. The results revealed that the alkane (paraffin) components were primarily responsible for the nephrotoxic activity seen in unleaded gasoline, with a positive structure-activity response relating the degree of alkane branching to the potency of the nephrotoxic response. In addition, the nephrotoxic activity observed with the naphtha streams and distillation fraction correlated well with the proportion of branched alkanes contained in each.     

Individual and population exposures to gasoline.

Gasoline is a complex mixture of many constituents in varying proportions. Not only does the composition of whole gasoline vary from company to company and season to season, but it changes over time. The composition of gasoline vapors is dominated by volatile compounds, while "gasoline" in groundwater consists mainly of water-soluble constituents. Hydrocarbons, including alkanes, alkenes, and aromatics, make up the large majority of gasoline, but other substances, such as alcohols, ethers, and additives, may also be present. Given this inability to define "gasoline,h' exposures to individual chemicals or groups of chemicals must be defined in a meaningful exposure assessment. An estimated 111 million people are currently exposed to gasoline constituents in the course of refueling at self-service gasoline stations. Refueling requires only a few minutes per week, accruing to about 100 min per year. During that time, concentrations in air of total hydrocarbons typically fall in the range 20-200 parts per million by volume (ppmV). Concentrations of the aromatic compounds benzene, toluene, and xylene rarely exceed 1 ppmV. Some liquid gasoline is also released, generally as drops less than 0.1 g each, but with enough larger spills to raise the average loss per gallon dispensed to 0.23 g for stations with conventional nozzles and 0.14 g per refueling for stations with vapor recovery nozzles (Stage II controls). Some skin exposure may occur from these spills but the exposure has not been quantified. Two major types of vehicular emissions have been studied. Evaporative emissions include emissions while the vehicle is driven (running losses), emissions after the engine has been shut off but is still warm (hot soak), and emissions during other standing periods (diurnal) emissions. These evaporative emissions are dominated by the more volatile gasoline components. Tailpipe emissions include some unreacted gasoline constituents as well as products of combustion (including chemicals identical to some of the original constituents of the gasoline) and a variety of hydrocarbons and related compounds. Running losses are reported to fall in the range of 0.2 to 2.8 g of total hydrocarbons per mile driven, while benzene evaporative emissions range from 0.002 to 0.007 g/mile. Benzene levels inside travelling vehicles have been reported to average about 13 ppbV in Los Angeles. Tailpipe emissions amount to 0.3 to 1.0 g/mile of total hydrocarbons; emissions of benzene, polycylic aromatic hydrocarbons, and 1,3-butadiene have been reported to range from 0.015 to 0.04 g/mile, 0.00025 to 0.00046 g/mile, and 0.001 to 0.005 g/mile, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)     

Interlaboratory comparison of a standardized toxicity test using the nematode Caenorhabditis elegans (ISO 10872)

A ring test was carried out within the standardization process of ISO 10872 to evaluate the precision of the toxicity test for the nematode Caenorhabditis elegans. Eight different laboratories tested aqueous solutions of the reference substance benzylcetyldimethylammonium chloride as well as native sediments and soils for toxic effects on the growth and reproduction of C. elegans. Validity criteria were met in all laboratories. Average median- and low-effect concentrations were determined to be 15.1 mg L(-1) (EC50) and 8.7 mg L(-1) (EC10) for growth and 7.5 mg L(-1) (EC50) and 3.8 mg L(-1) (EC10) for reproduction of C. elegans, with ECx values showing a high degree of reproducibility (CV(R) : <21% and <11% for EC10 and EC50, respectively) and repeatability (CV(r) : <20% and <7% for EC10 and EC50, respectively). The toxic effects of the sediments and soils revealed by the different laboratories were well related to each samples' degree of chemical contamination. Moreover, the effects showed an acceptable reproducibility (CV(R) : 5-33% and 0-28% for growth and reproduction, respectively) and repeatability (CV(r) : 3-13% and 0-12% for growth and reproduction, respectively). The present study confirms that the toxicity test with C. elegans according to ISO 10872 is a reliable and precise tool to assess the toxicity of aqueous media, freshwater sediments, and soils.     

Effects of an herbicide and insecticide mixture in aquatic mesocosms

A 1.8 m×2.5 cm reciprocating-plate countercurrent extraction column was evaluated for the preparation of WSF (water-soluble fractions) from Flotta North Sea light crude oil. The energy input from the plate reciprocation speeds was found to be the main factor affecting the characteristics of the extracted WSF, and the throughputs of the stock solution or the ratio of seawater to crude oil had little effect on the concentration and composition of the extracted WSF. A combination of a reciprocation speed of 170 strokes/min, a seawater flow rate of 220 ml/min, and a crude oil flow rate of 2.9 ml/min produced a WSF stock solution with a total hydrocarbon concentration of 13.5±0.30 mg/kg (n=6) which was more reproducible than that made by a previously used large-scale batch extraction method. A settlement time of 5 h or less for the stock solution allowed a full separation of any dispersed droplets of crude oil from the aqueous phase under the above conditions, but further increases in reciprocation speeds caused difficulties in the final separation of this crude oil. The column extraction method was highly reproducible and gave a more concentrated WSF containing a higher proportion of alkanes than a WSF made by the batch extraction method. Low-boiling aromatics were the main components of the total extracted hydrocarbons of the WSF.