Silica nanoparticles

Silica nanoparticles

Multiple application sectors

Silica is used by industry in a wide variety of applications. Synthetic amorphous silicas (SAS) are used:

• in food, as a food additive (E551) or “processing aid”:
  • anti-caking agent in powdered foodstuffs (sugar, salt, flour, cocoa, and many dehydrated products such as soups, instant noodles, coffee, etc.)
  • or viscosity modifier in sauces, soups, dressings, etc.
  • we would absorb on average about 124 mg per day
  • authorized, including in nano form for precisely defined uses (powdered foodstuffs, sugar, salt, seasoning, rice…) in 2009
  • its safety is questionable.
• as a moisture absorber in many products (including baby diapers and sanitary pads)¹Two reports from Anses show this (without specifying the potential associated risks):
  – Safety of baby diapers – Revised opinion of Anses, Collective expertise report, Anses, January 2019
  –Safety of intimate protection products, Anses, December 2019: the study of the national registry of substances in the nanoparticulate state (r-nano) confirmed that “Silica in the nanoparticulate state is used for its “superabsorbent” properties. It is notably sold to actors involved in the manufacture of diapers and sanitary pads.”)
• as reinforcing or thickening agents in various systems (elastomers, resins, paints, inks)
• in beer and wine as clarifying agents
• as texturizing / fluidizing agents for cosmetic (lipsticks, shampoos, creams), pharmaceutical or toothpaste products
• for non-stick coating²Cf. e.g. “Nanomaterials – Silica coating more slippery than Teflon”, Die Welt, March 2010 (like Teflon).

Presence of silica nanoparticles in France

According to the Ministry of Ecological Transition and Solidarity³Cf. bilan R-nano 2019, Ministry of Ecological Transition and Solidarity, June 2020, between 10,000 and 100,000 tons of silicon dioxide (SiO2) nanos were officially imported or manufactured in France in 2018. This range is not very precise and should be considered as an indication. Indeed, the quantities registered in the French R-nano register are below the quantities actually present on the French market, as many nanomaterials escape declaration.

Since the implementation of the declaration of “substances in nanoparticulate form” in 2013, it has been confirmed that different nanoforms of silica are imported or produced in France. Several forms of substances in the nanoparticulate state have been declared, under different names: “silica gel”, “silicon dioxide”, “synthetic amorphous silica”, “salicylic acid – magnesium salt”, “silane”, “silicon dioxide”, “silicate”, “silane”, “dichlorodimethyl-“, “products of silica reaction”).

Almost all (if not all) of the primary silica particles used are nanomaterials:

• SAS used in the food industry (E551), according to the sectoral regulations (Inco and Novel food and the definition recommendation of the European Commission)⁴Cf:
  – Tests conducted by Agir pour l’Environnement and published in June 2016 found 100% nanoparticle-sized silica in a Carrefour guacamole spice mix
  – Inventory of Nanotechnology applications in the agricultural, feed and food sector, RIKILT & JRC, EFSA supporting publication, 2014
  – Presence of nano-sized silica during in vitro digestion of foods containing silica as a food additive, Peters et al, ACS Nano, 6(3): 2441-2451, 2012
  – Presence and risks of nanosilica in food products, Dekkers S et al, Nanotoxicology, 5(3), 393-405, 2011, the [nano] mention should appear in the list of ingredients after the term E551 or silica, but at the end of 2018, this labeling was not often respected by manufacturers.

• SAS used in cosmetics. In July 2019, the European Scientific Committee on Consumer Safety (SCCS) published its final opinion on the solubility of synthetic amorphous silica (SAS)⁵Opinion on solubility of Synthetic Amorphous Silica (SAS), Scientific Committee on Consumer Safety (SCCS), June 20-21, 2019 (Corrigendum of December 6, 2019) according to which hydrophilic and hydrophobic SAS are to be considered as insoluble or very slightly soluble; under the Cosmetics Regulations 2009, these two SAS are therefore to be considered as nanomaterials and should be labeled with the word [nano].

Vigilance is required because there are significant risks associated with silica nanoparticles.