Chemical Toxicity Correlations for Several Protozoas, Bacteria, and Water Fleas Based on the Abraham Solvation Parameter Model
Hoover, Kaci R., Flanagan, Kelly B., Acree, William E., Jr., Abraham, Michael H., Journal of Environmental Engineering and Science
Abstract: Chemical toxicity data for three species of water fleas (Daphnia magna, Ceriodaphnia dubia, and Daphnia pulex), two protozoas (Tetrahymena pyriformis and Spirostomum ambiguum), and one bacterium (Pseudomonas putida) were retrieved from the published chemical literature. The compiled data were correlated with the Abraham solvation parameter model. Derived mathematical correlations described the observed published toxicity data to within an overall average standard deviation of approximately 0.27 log units. Principal component analysis of the correlation equations showed that the water-octanol system is a poor model for nonspecific aquatic toxicity, but that the water-isobutanol and water-pentanol systems are much better models.
Key words: aquatic toxicities, median lethal molar concentration, polar narcosis, nonpolar narcosis, mathematical correlation, solvation parameter model, principal component analysis.
Resume : Les donnees de toxicite chimique de trois especes de puces d'eau (Daphnia magna, Ceriodaphnia dubia et Daphnia pulex), deux protozoaires (Tetrahymena pyriformis et Spirostomum ambiguum) et d'une bacterie (Pseudomons putida) ont ete extraites de la litterature chimique publiee. Les donnees compilees ont ete correlees en utilisant le modele de parametre de solvatation Abraham. Les correlations mathematiques derivees decrivent les donnees de toxicite observees publiees dans un intervalle de deviation standard d'environ 0,27 unites log. L'analyse des principales composantes des equations de correlation indique que le systeme eau-octanol est un mauvais modele pour la toxicite aquatique non specifique, mais que les systemes eau-isobutanol et eau-pentanol sont de bien meilleurs modeles.
Mots-cles : toxicites aquatiques, concentration molaire letale mediane, narcose polaire, narcose non polaire, correlation mathematique, modele de parametre de solvatation, analyse des composantes principales.
[Traduit par la Redaction]
Many new chemicals are produced and (or) identified each year as the result of new industrial or natural biological processes. Not all of these compounds are safe. Many exhibit adverse health and (or) environmental effects. Governing bodies have established standard test methods and experimental protocols for determining the median mortality lethal concentration, L[C.sub.50], for measuring the lowest-observed effective concentration (LOEC) for decreasing reproductive capacity or decreasing mobility, for evaluating the chronic toxicity, for determining decreased population growth, and for quantifying developmental toxicity at various life stages for several different aquatic organisms. Such experimental determinations are often very expensive and time consuming as several factors may need to be carefully controlled in order to adhere to the established, recommended experimental protocol.
Inter-laboratory variations may also occur due to how various researchers interpret a given toxicity endpoint. In the case of the aquatic toxicity test for the Daphnia magna water flea, several research groups have determined the median immobilization effective molar concentration, -log E[C.sub.50], by counting the number of water fleas that were unable to swim their body length in 15 s after exposure to a given toxicant for the specified time period. Other researchers have taken the lack of translational movement (i.e., swimming) as a sign of organism death, and thus have reported their experimental data as the median lethal molar concentration (at times referred to as median acute immobilization molar concentration), -log L[C.sub.50]. The experimental observation, lack of translational movement after gentle prodding or stirring or exposure to bright light, is the same; however, the endpoints are labeled differently. A few researchers have tried to distinguish "death" versus "immobilization" by examining the non-swimming daphnids with a hand-held magnifying glass or under a dissecting light microscope to look more carefully for vital life signs. …