Abstract: Toxicity to the ciliate Tetrahymena pyriformis (log(IGC(50)(-1))) for 39 halogen-substituted alkanes, alkanols, and alkanitriles were obtained experimentally. Log(IGC(50)(-1)) along with the hydrophobic term, logK(ow) (1-octanol/water partition coefficient) and the electrophilic parameter, E(lumo) (the energy of the lowest unoccupied molecular orbital) were ...