Table 2. Chromosomal aberration frequency in Caco-2 cells following exposure to fumed or precipitated SiO2 particles
| Treatment | Conc. (µg/mL) | S9 mix | Number of structural aberrations | Gap | Total aberration cells (Excl Gaps) | Total aberration frequency (%) |
| Chromatid type | Chromosome type | Fragmentation |
| Break | Exchange | Break | Exchange |
| Control | 0 | - | 0 | 0 | 0 | 1 | 3 | 0 | 4 | 2.0 |
| Positive control (MMC) | 0.2 | 1 | 0 | 0 | 4 | 25 | 2 | 30 | 15.0 |
| Fumed SiO2 | 1,000 | 0 | 0 | 0 | 1 | 3 | 1 | 4 | 2.0 |
| Precipitated SiO2 | 1,000 | 0 | 0 | 0 | 1 | 4 | 2 | 5 | 2.5 |
| Control | 0 | + | 0 | 0 | 0 | 1 | 3 | 1 | 4 | 2.0 |
| Positive control (CPA) | 10 | 2 | 0 | 0 | 2 | 28 | 2 | 32 | 16.0 |
| Fumed SiO2 | 1,000 | 0 | 0 | 0 | 3 | 2 | 0 | 5 | 2.5 |
| Precipitated SiO2 | 1,000 | 1 | 0 | 0 | 2 | 2 | 0 | 5 | 2.5 |
Conc, concentration; Excl, excluding; MMC, mitomycin C; CPA, cyclophosphamide; −, without; +, with.