Figure 4: Effect of Ag exposures on cholinesterase activities. Symbols as in Figure 2. The symbols over the diagram are different for significant differences: for AChE (Latin letters) the dose dependence is significant among all the the concentrations, except the last two, while a significant threshold of effect is present for PChE (Greek letters) between 0.001 and 0.01 mg/L and between 0.01 and 0.1 mg/L Ag suspension. PChE shows the presence of aspecific enzymes able to cleave pTChI.