Long-term Toxicity Tests Research Articles

Treatment of municipal waste water by reverse osmosis and activated-carbon-removal of organic micropollutants and reduction of toxicity

A study on chemical and toxicological aspects of potable re-use of municipal waste water has been carried out using the effluent of a sewage treatment plant purified by a system including reverse osmosis and activated carbon filtration. The study included identification of organic micropollutants, the detection of the mutagenic activity and a long-term toxicity test with the amphibian Xenopus laevis. The majority of the identified organic micropollutants were removed by reverse osmosis and by subsequent activated carbon filtration. However, trihalomethanes, dichloromethane and alkylphenols were not removed by this system. Mutagenic activity has been detected in the biological effluent and to a lesser extent in the permeate of the reverse osmosis. No mutagenic activity was observed in the final product water. The results of the toxicity study with Xenopus laevis suggest no differences between the final product water and tap water with respect to chronic toxicity for the organisms.

Studies on the toxicity of tribromoethene, cyclohexene and bromocyclohexane to different freshwater organisms

In order to get an impression about the possible environmental effects of tribromethene. cyclohexene and bromocyclohexane, short-term toxicity tests were carried out with green algae ( Chlorella pyrenoidosa), crustaceans ( Daphnia magna) and fishes ( Poecilia reticulata) and long-term toxicity tests with Daphnia magna. The LC(EC) 50 values from the short-term tests with tribromoethene, cyclohexene and bromocyclohexane were 3.5–7.2, 3.8–5.3 and 2.2–2.5 mg 1 − respectively, whereas the lowest NOEC (No Observed Effect Concentration)-values from these tests were 0.52, 0.22 and 1.1 mg 1 −1 respectively; based on the criterion reproduction in the long-term tests the NOEC-values were 3.1, 2.4 and 0.5 mg 1 −1 respectively; All these values were corrected for the actual concentrations during the experiments and the tests were carried out in completely closed systems: in open systems the concentration of the test compounds decreased more than 90% within 48 h. Based on the log p (octanol-water partition coefficient) the calculated bio-accumulation factor value for tribromoethene and bromocyclohexane was 160, and for cyclohexene was 16. As for water quality criteria, values of 0.2 mg 1 −1 for tribromoethene, 0.01 mg 1 −1 for cyclohexene and 0.4 mg 1 −1 for tribromoethene 0.01 mg 1 −1 for cyclohexene and 0.4 mg 1 −1 for bromocyclohexane are proposed.

Cytotoxic compound shows antitumor activity

Fredricamycin A is an unusual molecule. First isolated from soil samples in Fredrick, Md., from which derives its name, excites the interest of scientists principally because shows promising activity both as an antibiotic and as an antitumor drug. Its structure, too, is unusual, and, therefore, intriguing. And its novel structure makes even more interesting as a potential new drug: Should prove useful could be the first of a whole family of new drugs. Not that its usefulness as a drug is certain by any means. Early tests of its biological activity look very promising, but long-term toxicity tests and clinical trials with the compound remain to be done before its potential usefulness can be evaluated. In addition, has solubility problems, at least in early tests, so that more pharmacological studies will be needed to find the best method of administration. Still, it is one of the most cytotoxic ...

Use of Fish Ventilation Frequency to Estimate Chronically Safe Toxicant Concentrations

Abstract A 96-hour toxicity test with fish ventilation frequency as the response variable was developed to estimate safe zinc concentrations for steelhead Salmo gairdneri. Two Oregon steelhead strains were exposed to zinc at different water temperatures and total hardnesses (7, 12, and 17 C; 25 and 125 mg/liter as CaCO3). Ventilation frequencies enumerated from bioelectric potentials generated by buccal and opercular openings and closings showed significant increases at the highest test concentration in five of 10 tests. At 12 C and 25 mg/liter hardness, responses were detected at a zinc concentration of 144 μg/liter; the “safe” concentration determined in a chronic exposure of embryos and juveniles was between 444 and 819 μg zinc/liter. This indicates that ventilation-frequency tests are at least as sensitive as long-term toxicity tests and may be used to screen chemicals for potential harmful effects on fish.

Substitutes for phosphate containing washing products: Their toxicity and biodegradability in the aquatic environment

The toxicity of nitrolotriacetic acid (NTA), citrex-S-5, sodium alluminium silicate (NAS), carboxymethyloxysuccinate (CMOS), linear alkylbenzene sulfonate (LAS) and soap was examined using bacteria ( Pseudomonas fluorescens ), algae ( Chlorella vulgaris and Microcystis aeruginosa ), crustaceans ( Daphnia magna ), insects ( Aedes aegypti ), fishes ( Poecilia reticulata and Oryzias latipes ) and amphibians ( Xenopus laevis ). The biodegradability of NTA, citrex-S-5, CMOS and LAS was studied in the OECD-test. The acute toxicity of the compounds differed largely with the organisms tested (up to a factor 1,000). Based on the results of the short-term toxicity tests (with all test organisms) and the long-term toxicity tests (with Daphnia magna and in case of LAS also with Poecilia reticulata ) the following no-observed-effect concentrations (NOEC) could be derived: LAS 3.2 mg/1; NAS and soap 10 mg/1; CMOS 32 mg/1; NTA 100 mg/1 and citrex-S-5 320 mg/1. However, testing different samples of one test compound may result in marked differences in toxicity (e.g. NAS: a factor 32). All compounds tested showed to be biodegradable as the percentage DOC decreased more than 80% within four weeks. CMOS biodegraded quickly, whereas citrex-S-5 and LAS showed a somewhat slower rate of degradation. In contrast to the other compounds NTA required an adaptation period of 1 week.

Serum oestrogen, progesterone and prolactin concentrations in cyclic, pregnant and lactating beagle dogs.

No correlations between the three hormones measured were found in any of the reproductive states examined. In 2 out of 8 dogs a negative correlation between serum progesterone and prolactin levels was found at Day 11 and Day 15, respectively (Day 0 = first day of copulation). In all of the 8 animals in which the progesterone and prolactin concentrations were measured in the same samples in late pregnancy, a negatively correlated overall pattern was obtained between both hormonal profiles. No correlation between serum oestrogen and prolactin levels was found. It is concluded that the proliferative mammary gland changes which are induced in female dogs during long-term toxicity testing with progestagens are unlikely to be related to prolactin or oestrogen synthesis and/or secretion.

Laboratory populations for long-term toxicity tests

International standardization of toxicity tests demands ‘standard’ animals. These are not to be found in nature, and transferring organisms from their natural habitat to the laboratory may add to the stress on them and interfere with the tests. Laboratory cultured animals may help reduce this problem.

Acute and chronic toxicity of furylfuramide in rats and mice.

As a model experiment on the study of toxicity of a compound, acute, short-term and long-term toxicity tests on Furylfuramide (2-(2-Furyl)-3-(5-nitro-2-8- furyl) acryl amide) were performed using Nitrofurazone (5-nitro-2-furaldehyde semicarbazone) and sorbic acid as control compounds. As the most conspicuous changes, hypertrophy of liver cells with clear cytoplasm was noted within a week of feeding. These cells were first located around the central vein and increased in number with time toward the peripheral portion of the lobule. In spite of the long-term experiments up to two years in rats and mice, no progressive lesion of the liver followed by the hypertrophy. No cumulative effect of Furylfuramide was noted in any organ. The hypertrophy of liver cells was reversible, when animals were switched to basal diet and kept on it for a certain length of time. A concentration of 0.125% in the diet was considered to be the tolerable safe dose of Furylfuramide. High incidence of spontaneous tumors developed in mice fed on Furylfuramide and control diet for two years was described. There was no difference in incidences between groups.

The wholesomeness of irradiated mushrooms

Six groups, each of ten male and ten female rats, received for 90 days either a standard diet or a diet containing 25% non-irradiated mushrooms, 25% 175- or 350-krad γ-irradiated mushrooms or 25% 250- or 500-krad electron-irradiated mushrooms. The mushrooms were cooked before the preparation of the diets. Concomitant with this 90-day test, a breeding experiment was carried out with four groups of 20 rats given the standard diet or a diet containing 25% mushrooms, non-irradiated or treated with the higher dose of γ or electron irradiation. From these animals three generations were bred. Animals of the first generation were used for a long-term toxicity test and animals of the third generation for a second 90-day test. No effects attributable to the treatment were observed on growth, food intake, composition of blood and bone marrow, the activity of serum glutamic-pyruvic transaminase, prothrombin time, organ weights or histopathology. The feeding of diets containing irradiated mushrooms had no effect on reproduction in these animals.

Methodology in long-term toxicity tests: A comparison of individual versus community housing

Rats raised in individual cages exhibited a slower growth rate than animals of the same age assigned to community housing. Other changes noted in the isolated rats included a significant lymphopenia, and alterations in the rate and pattern of organ growth and organ weight to body weight ratios. The direction and extent of the organ weight changes varied with the sex and strain of the test animal as well as the length of the test period. Histopathological changes were similar in both groups.

Effect of prolonged individual caging on toxicity parameters in rats

Prolonged individual caging of rats, as is sometimes employed in long-term toxicity tests, was accompanied by several changes in parameters of toxicity. In comparison to community-housed animals of same age and sex, acute LD 50s might be increased or decreased. Pentobarbitone and chloral hydrate sleeping times were reduced and the induction period for the loss of righting reflex with sodium amytal was prolonged. The extent of these changes was dependent upon the length of isolation, sex, and strain. A possible explanation for these altered toxic responses was that the adrenergic or ergotropic component of the central nervous system had undergone an increase in activity in the isolated animals.