The LC50 values for P. excavatus exposed to MTBE and TBA for 24, 48, and 72 h were 348–177 lg cm2 and 271–102 lg cm2, respectively (Table 2, Fig. 1A and B). The LC50 values for E. andrei were 387–336 lg cm2 for MTBE and 332–184 lg cm2 for TBA (Table 2, Fig. 1C and D).