Fish critical cellular residues for surfactants and surfactant mixtures

The feasibility of using in vitro methods to predict in vivo critical body residue (CBR) for single surfactants and mixtures by measuring the critical cell residue (CCR) in a hepatic fish cell line (PLHC-1C) was investigated. The CCR values were determined using radiochemical methods to measure the test compound partitioning between media and cells at varying concentrations for three distinctly different surfactants (anionic, cationic, and nonionic) and their mixture. The cell median effective concentration (EC50) values for hexadecyltrimethylammonium chloride (C16TMAC), dodecyl hexaethoxylate (C12E6), and sodium dodecylbenzene sulfonate (C12LAS) ranged from 2.9 to 163.3 microM, a 54-fold difference. These cell EC50 values indicate that the cells are several-fold less sensitive to surfactants than whole organisms are. However, based on cellular residue levels for each surfactant and their mixture, only an approximately threefold difference was observed with a range of 0.6 to 1.8 mmol/kg. These concentrations correspond closely to in vivo body burdens (0.2-8 mmol/kg) associated with nonpolar organic or narcosis-acting compounds and their mixtures. The CCRs could provide an alternative and rapid technique to predict CBRs.