Figure 5: Changes in TUNEL Labelling Index percentage of pulmonary cells, caused by i.t. exposure to CdCl2 versus SiNPs-Cd or SiNPs, calculated at three different time points (24 hr, 7 and 30 days). In all treated groups, a significant increase of apoptotic cells was detected, more manifestly 24 hr after treatment, ongoing until 30 days, displaying a decreasing tendency with time. The alteration showed the following trend: SiNPs-Cd >CdCl2>SiNPs. Data are expressed as mean ± SD (*) indicates statistically significant differences (p<0.05) compared to the respective control. Diverse letters (ac) denote mean values that are statistically different at p<0.05: comparison is between one time point versus the one immediately before of the same group.