Table 4.
Genotoxicity of silica in vivo (including data of non-food-grade and colloidal SAS)
| Species, exposure route, dose levels | Test substance | particle size and/or SSA | Source | Method | Result | References |
|---|---|---|---|---|---|---|
| Ex vivo gene mutation tests | ||||||
| F-344 rat, inhalation, 50 mg/m3, 13 weeks | Pyrogenica silica (AEROSIL® 200) | 200 m2/g | Degussa | HPRT mutations in alveolar type II cells | Negative, highly cytotoxic | Johnston et al. (2000) |
| In vivo micronucleus tests | ||||||
| Sprague–Dawley rat, m (up to 5/group); gavage, 5, 10, 20 mg/kg bw/day on 3 consecutive days | Pyrogenic silica (NM-202, -203) precipitated silica (NM-200, -201) |
10–22 nm | JRC | OECD TG 474 (1997) (combined with comet assay), bone marrow | Negative | Nanogenotox (2013), (NANOGENOTOX (2013) and Tarantini et al. (2015a) |
| Colon micronucleus assay (combined with comet assay) | Negative (NM-200, -201), borderline at lowest dose (NM-202,-203) |
|||||
| I CR mouse, gavage, 500, 1000, 2000 mg/kg bw, in 10 mL distilled water/kg | Colloidal silica* | 20, 100 nm | E&B Nanotech Co Ltd | OECD TG 474 (1997), GLP; bone marrow | Negative | Kwon et al. (2014) |
| Sprague–Dawley rat, m (up to 5/group); 3, 6, 12 mg/kg bw/day by intratracheal instillation and 5, 10, 20 mg/kg bw/day by iv injection (iv only NM-203); on 3 consecutive days | Pyrogenic and precipitated silica (NM-200, -201, -202, -203) | 10–22 nm | JRC | OECD TG 474 (1997) (combined with comet assay), bone marrow | Negative (intratracheal instillation) equivocal (iv, at highest dose corresponding to LD50) |
Nanogenotox (2013), NANOGENOTOX (2013) and Guichard et al. (2015b) |
| Wistar rat, m, f, inhalation 1, 5, 25 mg/m3, 14 day + 14 day recovery | Precipitated silica (NM-200) | 190 m2/g | JRC | OECD TG 474, polychromatic bone marrow erythrocytes, GLP | Negative | Knebel et al. (2014) |
| CR rat, m (5/group), inhalation (nose only), 7x10e7 and 1.8x10e8 particles/cm3 (1.8 and 86 mg/m3) for 1 or 3 day | Pyrogenic silica, de novo synthesised* | 37, 83 nm | Laboratory | Micronucleus assay in peripheral blood cells by flow cytometry; lung pathology and inflammatory parameters | Negative, no adverse effects on lung, no inflammation | Sayes et al. (2010) |
| Wistar rat, m (4–8/group), iv, 25, 50, 125 (55 nm only) mg/kg bw/day for 3 days | Colloidal silica (Levasil® 200, Levasil® 50)* | 15, 55 nm; 200, 50 m2/g | HC Starck | Combined micronucleus/comet assay; micronuclei in peripheral blood; test substance diluted and neutralised before injection into tail vein | Small increase in micronucleated reticulocytes at MTD, but not at lower doses | Downs et al. (2012) |
| In vivo chromosome aberration | ||||||
| Sprague–Dawley rat, m (1 and 5 × 1.4–5000 mg/kg bw, oral) | Silica gel (Syloid® 244) |
2.5–3.7 µm | nr | Chromosome aberration in bone marrow cells; animals killed 6, 24, or 48 h after single administration or 6 h after last administration in the repeated-dose experiment | Negative | US-FDA 1974 as cited in ECETOC (2006) |
| In vivo comet assays | ||||||
| Sprague–Dawley rat, m (up to 5/group); 5, 10, 20 mg/kg bw/day by gavage and iv (iv only for NM-203); up to 12 mg/kg bw/day by instillation; on 3 consecutive days | Pyrogenic and precipitated silica (NM-200, -201, -202, -203) | 10–22 nm | JRC | Combined comet/micronucleus assay; liver, kidney, blood, bone marrow; for the oral route in addition: duodenum and colon; For the instillation route in addition: lung, BAL fluid. |
Negative (in all organs and tissues), no overt toxicity except for iv route (LD50) | Nanogenotox (2013), Tarantini et al. (2015a), and Guichard et al. (2015b) |
| Sprague–Dawley rat, gavage, 500, 1000, 2000 mg/kg bw, at 0, 24 and 45 h before killing | Colloidal silica* | 20, 100 nm | E&B Nanotech Co Ltd | OECD TG 489, GLP; liver, stomach | Negative | Kwon et al. (2014) |
| Wistar rat, m,f, inhalation 1, 5, 25 mg/m3, 14 day + 14 day recovery | Precipitated silica (NM-200) | 190 m2/g | JRC | Ex vivo comet assay (± hGOOG1) in alveolar macrophages from BAL; immunohistochemistry in lung epithelial cells | Macrophages: small, concentration-dependent increase in DNA damage, particularly after the recovery period; no oxidative damage; particle aggregates/agglomerates in cytoplasm of intraalveolar macrophages; in lung epithelial cells slight, but significant increase in 8-OH-dG positive nuclei at d1 and d14 post-exposure | Knebel et al. (2014) |
| Wistar rat, m (4–8/group), iv, 25, 50, 125 (55 nm only) mg/kg bw/day for 3 days | Colloidal silica* (Levasil® 200, Levasil® 50) | 15, 55 nm; 200, 50 m2/g | HC Starck | Combined comet/micronucleus assay; test substance diluted and neutralised before injection into tail vein; organs examined: liver, lung, white blood cells | 15 nm: small increase in DNA damage at 50 mg/kg bw 55 nm: ↑DNA damage (1.5–1.7 ×) at 125 mg/kg in liver (MTD) |
Downs et al. (2012) |
| Rat, single intratracheal instillation, 360 µg | Colloidal silica* (Levasil®) | 15, 55 nm; | Akzo Nobel | Lung, bone marrow, 3 day after instillation | Negative, pulmonary inflammation (more pronounced with 15 nm) | Maser et al. (2015) |
| Drosophila tests | ||||||
| Drosophila melanogaster | Colloidal silica* (Levasil®) | 6, 15, 30, 55 nm and micron-sized, 50–450 m2/g | HC Starck | Wing-spot and comet assay (± FPG) in larvae haemocytes: larvae were fed 0.1–10 mM | Negative (no significant increases in the frequencies of somatic and recombination mutants); >5 mM: DNA damage (both ± FPG) |
Demir et al. (2015) |
BAL bronchoalveolar lavage, FPG formamido pyrimidine glycosylase, HPRT hypoxanthine phosphoribosyltransferase-encoding gene mutation, iv intravenous, m male, MTD maximum tolerated dose, nr not reported)
* Substance which does not fulfil the current EU criteria for E 551 (no star does, however, not implicate that the substance would be in compliance with EU E 551 specifications)
aIn publication erroneously described as “precipitated silica”