Amorphous Silica

Amorphous silica (fumed or precipitated silicon dioxide, CAS 7631-86-9) is the form of silica used as an abrasive in automotive rubbing compounds and polishing pastes. It is distinct from crystalline silica (quartz or cristobalite) — the IARC Group 1 carcinogen form — and is not classified as carcinogenic under repeated exposure. OSHA treats amorphous silica as inert nuisance particulate. In headlight restoration compounds, amorphous silica provides the abrasive cutting action at 15–40% concentration. Wet-sanding and wet-application processes reduce inhalation exposure substantially compared to dry abrasive use.