Table 1.

Analysis of TiO₂-nanoparticle distribution 1 h after exposure.

Compartment	NO	P	NE	RDI	Χ2	Fraction of total Χ2
Air	348	2251	378	0.920	2.42	0.071
Epi/Endo	29	151	25	1.143	0.52	0.015
CT	28	63	11	2.645	28.64	0.842
Caplum	44	207	35	1.265	2.44	0.072
Total	449	2672	449		34.02

Note. From the observed number of particles (N_O) and the number of points (P) on each compartment the expected number of particles (N_E) was calculated (e.g. N_E (air) = 449 × (2251/2672) = 378). The RDI is calculated from N_O/N_E (e.g. RDI (air) = 348/378 = 0.92). The chi-squared (Χ²) values are calculated from (N_O - N_E)²/N_E (e.g. Χ² (air) = (348–378)²/378 = 2.42). With three degrees of freedom (2-1 groups × 4-1 compartments) and a total chi-squared value of 34.02, the null-hypothesis of random distribution has to be rejected (p < 0.01). The connective tissue has an RDI of 2.645 and a partial chi-squared value that contributes about 84% of the total chi-squared. It is the only compartment that meets both criteria for a preferential deposition. Abbreviations: Air: Air space; Epi/Endo: Epithelial/endothelial cells; CT: Connective tissue; Caplum: Capillary lumen. Χ²: Chi-squared test values. N_O: Observed number of particles. N_E: Expected number of particles. RDI: Relative deposition index.