New insights into binary mixtures toxicology: 1. A case study of several saturated and unsaturated congeneric carboxylic monoesters based on the Köln model and Hydractinia echinata toxicity screening test system (VII)

Abstract

In this paper, a toxicity study is presented for a series of congeneric saturated and unsaturated carboxylic monoesters R1 – C(O) – R2, which is based on the metamorphosis of the organism Hydractinia echinata from larva to polyp under the influence of CsCl in the seewater alkaline medium as Toxicity Screening Test System (TSTS). In experimental conditions, the esters undergo a rapid and total abiotic hydrolysis reaction with the formation of the alcohol – carboxylate mixture in stoichiometric proportion. The studied ester concentration (mol/L) which determines the reduction of metamorphosis by 50% compared to the control is termed Metamorphosis Reducing Concentration (MRC50) and represents in the form of the logarithm of the reciprocal value (log 1/MRC50) the measured ester toxicity, marked as Mes; according to the algorithm proposed by the Köln model of investigation (KM), the predictions of toxicity values for untested derivatives are represented by the calculated Ces values that fall within a range of ±0.50 log u. compared to the corresponding values Mes. In the binary mixture, alcohol makes its mark on the whole process because depending on its nature and concentration it also facilitates the access of carboxylic acid through the cell membrane: in the interaction with cellular receptors (CR), the alcohol therefore represents the system fingerprint (FP). It can be noted that the values of Mes are different from those corresponding to the theoretical additivity (Ʃ) resulting from the sum of the individual toxicities of alcohols (Mal) and acids (Mac) and evolve according to the Class Regulated Increased Toxicity (CRIT).The different behavior of the two combined components with that of the individual derivatives, as well as the validity of the investigation model, are also confirmed by the published toxicity results data for three other aquatic organisms.