Quartz (Crystalline Silica)

Quartz (CAS 14808-60-7) is the crystalline form of silicon dioxide (SiO₂), one of the most abundant minerals in Earth's crust. In anti-seize pastes, it appears at trace concentrations (typically <1–5%) as a naturally occurring component of the mineral fillers used in the formulation.

The primary health concern for crystalline silica is occupational inhalation of respirable-size particles (PM10 or finer) during activities that generate silica dust — mining, sandblasting, cutting stone, and demolition. Chronic inhalation causes silicosis (progressive fibrous scarring of lung tissue) and significantly elevates lung cancer risk. This has led to IARC Group 1 (human carcinogen) and NTP Known Human Carcinogen designations, and to California Prop 65 listing for cancer.

In anti-seize compounds, the quartz is fully encapsulated in a petroleum-grease carrier and does not generate respirable dust during normal brush application. Henkel's own SDS §11 for Loctite LB 8008 explicitly states: "The crystalline silica present in this product is encapsulated in the liquid and will only be liberated if the product is sanded or abraded." The H372 STOT RE Cat 1 classification at the product level is a regulatory requirement based on the ingredient's known occupational hazard profile, not a reflection of the inhalation risk during normal paste application. The classification is required by OSHA HCS when the ingredient exceeds certain concentration thresholds in the mixture.

Regulatory status

• California Prop 65 listed for cancer: "Silica, crystalline (airborne particles of respirable size)," listed 1988-10-01 (mechanism: State Qualified Experts). Confirmed directly on the OEHHA list. Note the listing's own name scopes it to airborne particles of respirable size, which is the same encapsulation distinction the health hazard profile above already draws: the regulatory listing and the realistic paste-use exposure pathway are not the same thing, but the listing itself is real and applies to this substance under this identity, unlike the other ingredient files corrected alongside this one in the same audit pass.

Sources

• OEHHA Proposition 65 list cross-check: data/prop65/oehha-list.json (986 entries, published 2025-12-05), name match "Silica, crystalline (airborne particles of respirable size)," cancer, dateListed 1988-10-01. The OEHHA entry carries no CAS number of its own (a category-style listing rather than a discrete-substance listing), so the match is by name; CAS 14808-60-7 (quartz) is the generally accepted identity for this listing in supplier SDS documents.
• Blast-radius note: both consuming products (u-pol-undercoating-protection-spray, loctite-lb-8008-c5-a-anti-seize) already resolve prop65_warning: true and cite crystalline silica directly by name and CAS in their own SDS-sourced rationale text, consistent with keeping this flag as true.