Peter Leeuwangh

Joint toxicity of mixtures of 8 and 24 chemicals to the guppy (Poecilia reticulata).

Abstract The acute median lethal concentrations of equitoxic mixtures of 8 and 24 toxicants with diverse modes of action to guppies were determined. To quantify the joint toxicity, the results are expressed by means of the Mixture Toxicity Index (MTI). The toxicity of the mixtures was near concentration addition. Concentrations of the chemicals of about 0.1 of their LC50s contributed to the toxicity of the mixtures.

Quantitative structure-activity relationships and mixture toxicity studies of chloro- and alkylanilines at an acute lethal toxicity level to the guppy (Poecilia reticulata)

Quantitative structure-activity relationships (QSARs) were calculated for the acute lethal toxicities (14-day LC50) to the guppy (Poecilia reticulata) of anilines, with several hydrophobicity characteristics and the Hammett sigma constant as parameters. Calculated and experimental Poct values and II constants were used as hydrophobicity characteristics. Introduction of Hammett constants improved the quality of the QSARs. Together with the QSAR studies the toxicities of mixtures of the anilines were determined. The toxicities of three mixtures did not deviate from concentration addition.

Short term toxicity of tri-n-butyltinchloride in rainbow trout (Salmo gairdneri Richardson) yolk sac fry

Abstract Rainbow trout in the yolk sac fry stage were continuously exposed to tri-n-butyltin-chloride (TBTC) at concentrations of 0, 0.2, 1 and 5 ppb (μg/liter) for 110 days. After a 10 to 12 days exposure period, at the transition of the yolk sac fry stage to the swimming fry stage, all fish of the 5 ppb group suddenly died without any preceding symptoms. Hydropic degeneration of tubule segments of the pronephros was the main finding in these animals, whereas no histopathological changes were noted in animals exposed to 0.2 or 1 ppb for 10 days. At these exposure levels TBTC induced a significant and dose-related growth retardation resulting in a 44% decrease of the body weights in the 1 ppb group at the end of the experimental period. Hemoglobin content of the blood was decreased in a dose-related fashion and the number of red blood cells was significantly decreased at the 1 ppb exposure level. Histopathologically hyperplasia of liver cells was observed and as a consequence, the relative liver weights were significantly increased in a dose-related manner (both at a concentration of 0.2 and 1 ppb TBTC). From this study it is concluded that the applicability of tributyltin compounds as molluscicidal agents for the vector control of schistosomiasis remains very doubtful, since the concentrations required to kill snails are of the same range as those inducing disturbances in young rainbow trout.

Fate and effects of the insecticide Dursban® 4E in indoor Elodea-dominated and macrophyte-free freshwater model ecosystems: I. Fate and primary effects of the active ingredient chlorpyrifos

The fate of the insecticide Dursban® 4E (active ingredient chlorpyrifos) and its effect on crustaceans and insects was studied in indoor experimental freshwater ecosystems that intended to mimick drainage ditches. A single dose (simulating aerial drift) was applied to achieve nominal chlorpyrifos concentrations of 5 or 35 μg/L. Two experiments were performed, one in which all model ecosystems were dominated by the macrophyte Elodea nuttallii, and one using systems devoid of macrophytes.In macrophyte-dominated systems, Elodea vegetation adsorbed a large proportion of the dose applied and hampered the mixing of the insecticide in the water (at least up till day 8). Only a small proportion became incorporated in the sediment. In open water systems the insecticide was rapidly mixed in the water, and the sediment played a very significant role as sink for chlorpyrifos. In both Elodea-dominated and open water systems 50% of the dose applied had disappeared on day 8 post-treatment. The rate of disappearance of chlorpyrifos was relatively rapid in water and macrophytes, and relatively slow in the sediment.Of the arthropods in the zooplankton Cladocera were more susceptible than Copepoda. Significant effects (p⩽0.05) on Cladocera occurred relatively late in Elodea-dominated systems (in week 4 post-application) in contrast to open water systems (week 1), which is in accordance with the observed differences in the fate of chlorpyrifos. Daphnia pulex, D. longispina and Simocephalus vetulus recovered in the model ecosystems when chlorpyrifos concentrations were lower than 0.1–0.2 μg/L, which is in agreement with results of laboratory protocol tests performed with these cladocerans.Among the macroscopic Arthropoda the apparent order of susceptibility was amphipods > insects > isopods. The isopod Asellus aquaticus was more sensitive to the application of the insecticide than the closely related species Proasellus coxalis. In treated open water systems the latter even increased significantly in numbers. Cage experiments in the model ecosystems performed with several species of Arthropoda indicate that laboratory protocol tests may give a reasonable prediction of short-term direct effects of chlorpyrifos for the same species inhabiting more complex aquatic systems.

Joint toxicity of mixtures of groups of organic aquatic pollutants to the guppy (Poecilia reticulata).

In this study acute lethal concentrations (LC50) to the guppy (Poecilia reticulata) were determined for mixtures of 4 groups of aquatic pollutants. The groups were composed of 11 nonreactive, nonionized organic chemicals, 11 chloroanilines, 11 chlorophenols, and 9 reactive organic halides. Earlier studies indicated that the joint toxicity within each of these groups was concentration additive, probably because of a similar mode of action. The joint toxicity of combinations of one representative from each group showed a high variance, but generally tended to be partially additive to concentration additive. This high variance is probably caused by the low number of compounds in these mixtures. Experiments with mixtures of whole groups gave more accurate results. The toxicity of a mixture of the first three groups, containing 33 well-known aquatic pollutants, was almost completely concentration additive. Concentrations of 0.04 of the individual LC50 values contributed to the toxicity of this mixture.

Hexachlorobutadiene residues in aquatic fauna from surface water fed by the river rhine

Hexachlorobutadiene (HCBD) was identified as a component of the residue mixture of chlorinated hydrocarbons in fish from inland waters fed by the Rhine, particularly in the Ketelmeer. The residue level in fish is related to the fat content; no bioaccumulation in the food chain to higher trophic levels was observed. HCBD concentrations in the water of the Ketelmeer appeared to be three orders of magnitude lower than those found in aquatic animals.