Development of methods for evaluating toxicity to freshwater ecosystems.

This article presents a summary of a collaborative research program involving five European research groups, that was partly funded by the European Commission under its Environmental Research Program. The objective of the program was to develop aquatic toxicity tests that could be used to obtain data for inclusion at Level 2 of the Risk Evaluation Scheme for the Notification of Substances as required by the 7th Amendment to EC Directive 79/831/EEC. Currently only a very limited number of test methods have been described that can be used for this purpose and these are based on an even smaller number of test species. Tests based upon algae (Chlamydomonas reinhardi, Scenedesmus subspicatus, and Euglena gracilis), protozoa (Tetrahymena pyriformis), rotifera (Brachionus calyciflorus), crustacea (Gammarus pulex), and diptera (Chironomus riparius) were developed. The tests encompassed a range of end points and were evaluated against four reference chemicals: lindane, 3, 4-dichloroaniline (DCA), atrazine, and copper. The capacity of the tests to identify concentrations that are chronically toxic in the field was addressed by comparing the effects threshold concentrations determined in the laboratory tests with those determined for similar and/or related species and end points in stream and pond mesocosm studies. The lowest no-observed-effect concentrations (NOEC), EC(x), or LC(x) values obtained for lindane, atrazine, and copper were comparable with the lowest values obtained in the mesocosms. The lowest chronic NOEC determined for DCA using the laboratory tests was approximately 200 times higher than the lowest NOEC in the mesocosms.

Paradoxical pulmonary embolism secondary to aortocaval fistula: diagnosis by helical CT.

Spontaneous aortocaval fistula is an unusual but well recognized complication of abdominal aortic aneurysm. Reports of aortocaval fistula as the source of pulmonary embolism are rare. We report a case of paradoxical pulmonary embolism secondary to an aortocaval fistula. The abdominal aortic aneurysm and the associated aortocaval fistula were well demonstrated on helical CT, leading to early diagnosis and prompt surgical treatment with good clinical outcome.

Result of angioplasty of brescia-cimino haemodialysis fistulae: medium-term follow-up.

AIM: To determine the results of transluminal angioplasty in patients with Brescia-Cimino arteriovenous fistulae. PATIENTS AND METHODS: Thirty-one patients underwent transluminal angioplasty of 36 stenotic lesions related to Brescia-Cimino arteriovenous fistulae over a 5-year period. The lesions treated were characterized by review of pre-angioplasty fistulograms. Medical and radiological records were reviewed to assess medium-term patency of each patient's fistula. RESULTS: Angioplasty was performed successfully in 28 out of 31 patients initially (90% technical success rate). Duration of follow-up for the 31 patients ranged from 4 to 65 months (median = 34 months). At 6 months, seven patients required further surgical or endovascular intervention (18 patients remained event-free) and at 1 year, 10 patients required further endovascular or surgical intervention (14 patients remained event-free). Life-table analysis revealed primary patency rates of 77%, 64% and 39% at 6 months, 1 year and 2 years, respectively. At 6 months and 1 year, four and five patients, respectively, required surgical revision or closure of fistula. Secondary patency rates were 85%, 81% and 65% at 6 months, 1 year and 2 years, respectively. All patients with a primary patency at 2 years remained event-free during the follow-up period. CONCLUSIONS: Transluminal angioplasty is an effective treatment for stenoses developed in relation to Brescia-Cimino haemodialysis fistulae. Further endovascular procedures may be required, especially in the first 24 months, to preserve patency. These techniques extend the lifetime of fistulae, thereby preserving proximal venous access sites for future use. Our result is in broad agreement with results from other series.

A pond mesocosm study to determine direct and indirect effects of lindane on a natural zooplankton community.

We assessed the threshold concentrations for toxic effects by lindane on a zooplankton community using mesocosms in a natural pond. Enclosures (1000 litres) were treated to give mean concentrations of 0, 2, 6, 12, 18, 24, and 50 microg litre(-1) over a test period of 39 days. Larvae of the phantom midge Chaoborus flavicans showed a high susceptibility to lindane and were virtually eliminated from enclosures with > or =12 microg litre(-1) 4 days after application. Populations of cyclopoid nauplii (Eucyclops serrulatus) were reduced at a lindane concentration of 2 microg litre(-1) and showed high mortality after 11 days exposure to > or =6 g litre(-1). No lindane-induced effects could be seen in the cladoceran species Daphnia longispina and Chydorus sphaericus. Rotifer species were probably not directly affected by lindane; however loss of the principal predator Chaoborus was accompanied by an increase in the numbers of Asplanchna priodonta. A simultaneous decrease in Keratella quadrata possibly reflected predation since its decline showed no dose-response relationship with lindane and it is among the major prey of Asplanchna. Such complex secondary effects, occurring through trophic interactions between a predator and two co-occurring prey, would not have been predicted from single-species toxicity tests. These, and effects on cyclopoid populations that occurred predominantly through the mortality of nauplii, demonstrate the value of toxicological studies on natural communities. We conclude that a combination of laboratory and field investigations, coupled with mono-species and community assessments, provide the best route for understanding the effects of toxicants such as lindane for regulatory purposes.

Toxicity of lindane to freshwater insect larvae in compartments of an experimental pond.

The acute and chronic toxicities of lindane to larvae of the freshwater insects Chironomus riparius Meigen, Chaoborus flavicans (Meigen), and Sigara striata (L.) were investigated in mesocosm compartments of an experimental pond. The following median lethal concentrations (LC50s) were determined: 240-hr LC50 of 2.0 micrograms lindane liter-1 for second instar C. riparius, 72-hr LC50 of 6.5 micrograms lindane liter-1 for fourth instar C. riparius, and 96-hr LC50s of 4.0 and 3.9 micrograms lindane liter-1 for fourth instar C. flavicans and fourth or fifth instar S. striata, respectively. Lindane significantly reduced the growth over 10 days of second instar C. riparius compared to that of the control at the treatment concentrations where larvae survived (1.0, 2.5, and 7.0 micrograms lindane liter-1). A significant increase in the median emergence time in comparison to that of the control was observed for C. riparius exposed to 0.8 and 2.0 micrograms lindane liter-1, with higher concentrations causing 100% mortality. The findings compare well with previously reported laboratory data on the toxicity of lindane to insects and support the methodology and results of a laboratory growth test for C. riparius.

Fate and effects of salicylic acid compounds in freshwater systems.

The comparative fates and effects of salicylic acid (SA) and Na salicylate in algae (Scenedesmus subspicatus, Monoraphidium minutum), in Lemna minor, and in Daphnia magna were examined. Test methods were principally based on the OECD testing guidelines with modifications in the procedures. The influence of fulvic acid (FA) on bioconcentration and on toxic effects was studied. FA addition significantly reduced the bioavailability of SA in L. minor and the algae species. SA was more toxic to Lemnaceae, algae, and daphnids than to its Na salt. Bioconcentration factors in S. subspicatus, M. minutum, and L. minor were about 10(3) in 72-96 hr. The reproducibility of D. magna was reduced by 38% at a concentration of 20 mg SA/liter.

Influence of benzene on the phytoplankton and on Daphnia pulex in compartments of an experimental pond.

Benzene, with initial concentrations of 100 and 50 mg per liter, was dosed in duplicates into four compartments of a small pond. The decrease of chemical concentration in the water was exponential with a mean half-life of 4.7 +/- 0.9 days. Following benzene application, the phytoplankton density and diversity slightly increased relative to the controls. Both concentrations were lethal for the daphnids present. During 24-hr in vitro tests with Daphnia pulex (initial benzene concentrations less than 50 mg per liter), a direct correlation between mobility and decreasing chemical concentration was observed.

Elimination- and biodistribution studies of [14C]dodecylbenzene sulfonate in rats, following low dosing in the daily diet and a single i.p. administration.

14C-labelled sodium dodecylbenzene sulfonate (DBS) was administered daily in the diet at a concentration of 1.4 mg/kg to male rats for 5 weeks. From the total uptake (1.213 +/- 0.08 mg/animal) of DBS, 81.8% was excreted during the dosing period; 52.4% in feces and 29.4% in urine. Low levels of [14C]DBS-derived residues were detected in all tissues analyzed on day 35 of the experiment. Following 1 week on normal diet only 7.8% of the nominally stored amount of 14C was found in the excreta. Single i.p. application of 0.385 mg [14C]DBS/rat (2.26 +/- 0.15 mg/kg body wt.) resulted in a total elimination of 94.5% within 10 days. 84.7% of the dose was eliminated in the first 24 h. All fecal and renal [14C]DBS-derived activity consisted of highly polar metabolites.

Long-term fate of organochlorine xenobiotics in aquatic ecosystems. Distribution, residual behavior, and metabolism of hexachlorobenzene, pentachloronitrobenzene, and 4-chloroaniline in small experimental ponds.

Hexachlorobenzene (HCB), pentachloronitrobenzene (PCNB), and 4-chloroaniline (4-CA) were dosed into the water of small experimental ponds in Southern Germany. The average concentration of the chemicals in the pond water during the application period (4-6 weeks) was about 50 micrograms/liter. Chemical residue concentrations were determined in water, sediment, and flora and fauna species up to 166 weeks after application. The decrease of all chemicals in the water phase follows exponential functions and can be correlated to some extent with the physicochemical properties such as volatility from water and vapor pressure. Although chemically quite different, the residual behavior of the model compounds followed a similar pattern resulting in relatively high initial concentrations in biota and a slow buildup and subsequent decline of concentrations in the sediment. As to some fauna species (backswimmers and libellula larvae) and to sediment (0- to 20-cm layers), even 3 years after application, 14C residues of about 0.1 mg/kg could be found. In all analyzed flora species, however, no more residues could be measured in the new vegetation period after application. The amounts of the chemicals used did not cause detectable symptoms of poisoning over the investigation period. Anisols and azo compounds were found to be conversion products of pentachloronitrobenzene and 4-chloroaniline.

Biotransformation and disposition of the coumaphos metabolite 3-chloro-4-methyl-(4-14C)-7-hydroxycoumarin in rats.

The biotransformation and disposition of 3-chloro-4-methyl-(4-14C)-7-hydroxycoumarin [(14C) chlorferron] were investigated in rats after single oral administration. Following administration of (14C) chlorferron at 0.5 and 20 mg/kg body weight to male rats, greater than 90% of the given dose was eliminated in the urine (77-84%) and faeces (7-15%) within 24 h. Low levels of (14C) chlorferron derived residues were detected in different organs of rats 7 days after dosing. Administration of (14C) chlorferron at 20 mg/kg allowed the isolation of three metabolites in the 24-h urine of male and female rats. Compounds tentatively identified were dechlorinated metabolites of chlorferron besides unchanged chlorferron. The majority of the metabolites were excreted in conjugated forms. The pattern of biotransformation of chlorferron was qualitatively similar in male and female rats. Comparative studies on the elimination and biodistribution of (14C) chlorferron and its parent compound (14C) coumaphos in male rats indicated rapid metabolism and faster elimination of chlorferron and its metabolites from the body than that of the parent compound.

Elimination pattern and biodistribution of [14C]chlorferron in rats.

Administration of [14C]chlorferron in a single oral dose of 0.5 and 20 mg/kg body weight to female rats resulted in a urinary excretion of greater than 74% of the given dose during the first 24 h. Approx. 8% of the dose was eliminated in faeces within 7 days. 7 days after dosing, very low levels of [14C]chlorferron-derived residues were detected in all analyzed organs. These findings indicated that chlorferron was absorbed from the gastro-intestinal tract in appreciable quantities, but was rapidly excreted mainly via the urine with small amounts only in the faeces.

Studies on 3-chloro-4-methyl-(4-14C)-7-hydroxycoumarin in rats.

The distribution, excretion and biotransformation of 3-chloro-4-methyl-(4-14C)-7-hydroxycoumarin [(14C) chlorferron] were studied in the rats after single oral administration. Male and female Wistar rats were given single oral doses of 0.5 and 20.0 mg/kg body weight of (14C) chlorferron and routes and rates of elimination of 14C activity were followed for 7 days. Following administration of 20 mg/kg, 96.74 +/- 3.68% and 94.98 +/- 6.15% of the dose were excreted by male and female rats, respectively. The excretion of total radioactivity after 0.5 mg/kg was significantly (P less than 0.05) higher in male rats (93.77 +/- 2.27%) as compared to female rats (87.23 +/- 1.96%). Approximately 80-90% of the excreted radioactivity was detected in urine. Analysis of urine showed no qualitative difference in the biotransformation pattern of (14C) chlorferron in male and female rats. (14C) chlorferron derived metabolites were excreted in both conjugated and unconjugated forms. After 7 days of dosing, very low concentrations of (14C) chlorferron derived residues were detected in different body tissues. No detectable sex difference in body distribution of radioactivity was observed. These results suggest that (14C) chlorferron is rapidly eliminated from the body and only small amounts are stored in the organs.

Metabolism of beta-hexachlorocyclohexane-14C in rats following low dosing in the daily diet.

beta-Hexachlorocyclohexane-14C (1.5 ppm) was administered in the diet to rats for one week. During the elimination phase three therapeutic agents were fed to enhance the clearance. Renal and fecal excreted radioactive products were collected for 8 weeks and extracted. Although significant differences in the total excreted amount of radioactivity were registered between controls and treated rats, there were no quantitative differences in the extractability of the excreta and no differences in the chemical nature of metabolites found. Radioactivity in urine consisted to 100% of conversion products, about 30% of which were unextractable residues. In the organic soluble fraction the 2,4,6-trichlorophenol was the major metabolite in urine and the only metabolite detected in feces. Minor conversion products of beta-HCH in urine were a trichlorohydroxyme-thoxybenzene, a dichlorophenol and a trace of a tetrachlorocyclohexane-isomer.

Fate of 2,5,4'-trichlorobiphenyl in rats.

1. Following the administration of daily oral doses (1 mg/kg) of 2,5,4'-trichloro-[14C]biphenyl to rats for 14 days, the compound was rapidly excreted, only small amounts (3--4%) being stored in the organs. 2. The majority of the biphenyl was metabolized (greater than 85%) and the major metabolites excreted were identified as hydroxy-, dechloro- and conjugated derivatives.