Fumed Silica Regulatory Overview: REACH, TSCA & More

Fumed silica (CAS 112945-52-5) is fully registered under EU REACH Regulation (EC) No 1907/2006 in the highest tonnage band (≥100,000 t/yr). The joint registration dossier, maintained by the Synthetic Amorphous Silica Consortium (SASi), covers all major producers including Evonik, Wacker, and Cabot. The substance is classified as non-hazardous — no CLP hazard classification is required and it does not appear on the SVHC Candidate List or Annex XIV authorization list.

Key dossier endpoints confirm low toxicity: no carcinogenicity (IARC Group 3 — not classifiable), no mutagenicity, DNEL for inhalation set at 4 mg/m³ (respirable dust). Nano-specific annexes apply when primary particles are 7–40 nm, requiring additional characterization under the 2020 REACH nano-amendment. Buyers importing into the EU should verify their supplier holds Only Representative (OR) status or is directly registered.

• Tonnage band — ≥100,000 t/yr — full CSR and exposure scenarios required
• Hazard classification — Not classified under CLP; no H-statements assigned
• SVHC status — Not on Candidate List; no authorization or restriction proposals pending
• Nano provisions — Primary particles 7–40 nm require REACH Annex VI–XI nano characterization

Under the US Toxic Substances Control Act (TSCA), synthetic amorphous silica is listed on the TSCA Chemical Substance Inventory under both CAS 112945-52-5 (pyrogenic/fumed) and CAS 7631-86-9 (generic SiO₂). No Significant New Use Rules (SNURs) or Section 6 risk management actions apply. EPA has reviewed SAS under the 2016 Lautenberg Act amendments without designating it as high-priority for risk evaluation.

For food-contact applications, FDA regulations permit fumed silica as a direct food additive under 21 CFR §172.480 (silicon dioxide) at a maximum level of 2% by weight of the food. It is also approved as an indirect food additive in food-contact materials under 21 CFR §178.3297. Food-grade fumed silica must meet USP/NF monograph specifications: ≥99.0% SiO₂ on ignited basis, loss on ignition ≤8.5%, and heavy metals ≤0.003%.

• TSCA listing — Active on TSCA Inventory; no SNUR or Section 5 notification required
• FDA direct additive — 21 CFR §172.480 — max 2% w/w as anti-caking agent in food
• FDA indirect additive — 21 CFR §178.3297 — permitted in food-contact coatings and polymers
• USP/NF purity — ≥99.0% SiO₂ (ignited), loss on ignition ≤8.5%, heavy metals ≤30 ppm

Fumed silica used in food processing and pharmaceutical formulations must meet distinct purity and characterization standards beyond bulk industrial grades. The European Food Safety Authority (EFSA) re-evaluated E 551 (silicon dioxide) in 2018, confirming its acceptable use as an anti-caking agent but recommending that nano-fraction characterization be improved by 2024. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) assigns an ADI of ‘not specified’ — meaning no toxicological concern at current usage levels.

In pharmaceuticals, fumed silica serves as a glidant (0.1–1.0% w/w in tablets) and viscosity modifier in topical formulations. The European Pharmacopoeia (Ph.Eur.) monograph 0434 and USP-NF monograph specify BET surface area reporting, residual chloride ≤0.025%, and arsenic ≤3 ppm. Buyers sourcing for these sectors should confirm certificates of analysis include particle size distribution, BET surface area (typically 150–400 m²/g), and extractable metals panels.

• E 551 (EU) — EFSA-approved anti-caking agent; nano-fraction review ongoing
• JECFA ADI — ‘Not specified’ — no upper intake limit set at normal usage
• Ph.Eur. glidant range — 0.1–1.0% w/w in solid dosage forms; BET 150–400 m²/g
• Key CoA parameters — Residual Cl⁻ ≤250 ppm, As ≤3 ppm, heavy metals ≤30 ppm

ISO 18473 (Parts 1–4) provides the primary international framework for characterizing synthetic amorphous silica. Part 1 covers classification and nomenclature, distinguishing pyrogenic (fumed), precipitated, gel, and colloidal forms. Part 3 specifically addresses pyrogenic silica, defining test methods for BET surface area (ISO 9277), pH (ISO 787-9), tapped density, and carbon content for hydrophobic grades.

For industrial buyers, compliance with ISO 18473-3 signals that a supplier follows standardized QC protocols. Additional relevant standards include ISO 3262-20 (extenders for coatings — precipitated silica), ASTM E2456 for nanotechnology terminology, and EN 15051 for dustiness classification. Formulators in coatings and sealants should also reference ISO 2813 (gloss measurement) when specifying matting grades, as BET surface area (200–300 m²/g typical for matting) directly correlates with gloss reduction efficiency.

• ISO 18473-3 — Pyrogenic silica characterization — BET, pH, tapped density, carbon content
• ISO 9277 — BET surface area determination via gas adsorption (N₂ at 77 K)
• EN 15051 — Dustiness classification — relevant for OEL compliance and handling
• ISO 2813 — Gloss measurement at 20°/60°/85° — critical for matting grade selection