Toxicity of simple mixtures to the nematode Caenorhabditis elegans in relation to soil sorption

Abstract

Single and combined toxicity of copper-zinc, copper-cadmium, cadmium-lead, copper-carbendazim, and copper-carbendazimiprodione to the nematode Caenorhabditis elegans in soil was studied. The one-week population increase was estimated as the toxicity endpoint. The aim was to study the relationship between mixture interactions in the soil and the combined toxic effect. Soil sorption was quantified using the Freundlich adsorption constant. Joint toxicity patterns were quantified by comparing mixture effects to the effect of individual constituents and were related to total metal concentrations in the soil, water-soluble concentrations, and 0.01 M CaCl2-extractable concentrations. The metal with the highest adsorption constant influenced the sorption of metal with the lowest adsorption constant when both were combined, indicating interaction. Consequently, both the composition of the mixture as well as the relative toxicity of individual mixture constituents differed between total, water-soluble, and CaCl2-extractable concentrations, which was taken into account in the data quantification procedure that was applied. Both the additive and the independent model were generally inadequate to describe the effects of metal mixtures. Compared to the additive model, synergism was observed at dose levels higher than the median effect isobole. A general relationship between mixture interactions in the soil and the combined toxicity was not found.

Gene-environment and protein-degradation signatures characterize genomic and phenotypic diversity in wild Caenorhabditis eleganspopulations

“…Previous studies on C . elegans have investigated the organism’s response to a wide range of different environmental factors, including exposure to different bacteria [7-9], pH [9], osmotic pressure [9,10], chemicals [11,12], and temperature [9,12-16], among others. As yet, however, these responses have not been tested in natural populations.…”

Worm variation made accessible

“…These efforts pave the way toward a widely available and usable resource for studies on natural genetic variation in C. elegans . This likely includes research on gene–environment interactions since C. elegans has been intensively used to study the effects of different stressors next to ambient environmental conditions 49 - 53 …”

An isobole-based statistical model and test for synergism/antagonism in binary mixture toxicity experiments

“…For each set-up we used three different coefficients of variation (CV) of the response. These were 5%, 15% and 25%, corresponding to the range of CV's of controls in commonly used test systems Fiebig et al 2003;Jonker et al 2004;Lauridsen et al 2003).…”

“…Such models, describing possible patterns of deviation from the reference, have been developed (Carter 1995;Greco et al 1995;Haas et al 1996;Jonker et al 2004), and are usually termed response surface models. Essentially a dose-response relation for each chemical applied separately is combined with a functional relationship between the concentrations of the individual chemicals in the mixture, and the single-chemical concentrations needed to obtain the same effect.…”