Sodium fluosilicate
CAS No. 16893-85-9

Return to Adverse Effects

ACTIVITY: Insecticide, Wood preservative, US EPA List 3 Inert (Inorganic)

The major use is as a fluoridation agent for drinking water.

Adverse Effects:

Body Weight Decrease
(including Cachexia, Wasting, Anorexia)

Poisoning Incident

Regulatory Information
(only comprehensive for the US)
US EPA Registered:

US EPA List 3 Inert

US EPA PC Code: 075306 
California Chemical Code 538 
Registered use in
(includes only a limited list of countries)

Australia, Canada, India, South Africa, Tanzania, US, Vietnam 
European Commission: Not allowed to be used as an active ingredient after July 25, 2003. 
Other Information
Molecular Formula: F6 Na2Si
Manufacturers: Panorama 
Other Names:

Sodium fluorosilicate
Sodium hexafluorosilicate
Sodium silicofluoride
Sodium silica fluoride
Nox-All Earwig Bait Brand
-- see more synonymns in box at bottom of page

Of special interest:
PAN Data
October 2001 - Toxicological Summary for Sodium Hexafluorosilicate [CASRN 16893-85-9] and Fluorosilicic Acid [CASRN 16961-83-4]. Review of Toxicological Literature. Prepared for Scott Masten, Ph.D., National Institute of Environmental Health Sciences.  
TOXNET profile from Hazardous Substances Data Bank 
November 26, 2002 - European Commission: Sodium Fluosilicate is one of 320 pesticides to be withdrawn in July 2003. Some 320 substances used in plant protection products (PPPs) - including insecticides, fungicides and herbicides - are to be withdrawn from the market by 25 July 2003 as part of the European Commission's new approach to the evaluation of active substances in plant protection products. This aims to improve safeguards to ensure that all such products in use are safe for the environment and human health. Users, wholesalers and retailers of plant protection products will need to be aware of whether the products they use or sell are likely to be withdrawn, so as to prevent them being left with stocks of unusable material. Those concerned should contact their national authority to check the authorisation status for any particular product. The Regulation (ní 2076/2002 of 20 November 2002), with the list of the 320 substances, has now been published in the Offical Journal. Ref: MIDDAY EXPRESS. News from the Press and Communication Service's midday briefing. 
April 9, 2001. Australia. Exemptions Listing
TECHNICAL GRADE ACTIVE CONSTITUENTS EXCLUDED FROM THE REQUIREMENTS OF NRA APPROVAL The list generally includes chemicals which have not been primarily developed as agricultural chemicals and thus for which an extensive package of data would not be readily available. Approval by the National Registration Authority for these TGACs is currently not required. Fluoride compounds exempted include: Cupro-ammonium Fluoroborate complex, Sodium fluoride, Sodium fluoroacetate, Sodium fluorosilicate.
July 11, 2001 - Material Safety Data Sheet. GM Foam Gelling Agent. GM Foam, Inc.
DOT Shipping Name: Latex Intermediate.
August 1999 - Hazardous Substance Fact Sheet - New Jersey Dept. of Health & Senior Services  
Product Data and Uses - PELCHEM 
June 21, 2001 - Hazardous Materials Regulations for Fluoride/fluorinated substances, Federal Register on Harmonization of international shipment of Dangerous Goods. Final Rule.   
Online as of December 2, 2001 - Listed as a "Deleterious Substance" under the "Poisonous and and Deleterious Substances Control Law" by the National Institute of Health Sciences in Japan.
Insecticide products - partial list

US EPA List of Inerts. This substance is on List 3.

Note: US EPA allows so-called "Inert" ingredients to be commonly mixed with the "active" pesticidal ingredient to create a formulated pesticide product. According to EPA, "The term `inert' is not intended to imply nontoxicity; the ingredient may or may not be chemically active." "Inert" ingredients include solvents, emulsifiers, spreaders, and other substances mixed into pesticide products to increase the effectiveness of the active ingredients, make the product easier to apply, or to allow several active ingredients to mix in one solution. Both US EPA and California Department of Pesticide Regulation require pesticide manufacturers to identify inert ingredients in their products but do not disclose this information to the general public because the pesticide industry considers product formulations trade secrets, protected by law and by the US EPA. The US EPA category of Inerts (as of September 2003):

List 1 - Of Toxicological Concern
List 2 - Potentially Toxic / High Priority for Testing
List 3 - Of Unknown Toxicity
List 4A - Generally Regarded as Safe
List 4B - EPA states it has Sufficient Information to Reasonably Conclude that the Current Use Pattern in Pesticide Products will not Adversely Affect Public Health or the Environment
List 4 (all)

See good report: Toxic Secrets": "Inert" Ingredients in Pesticides 1987-1997, published by Northwest Coalition for Alternatives to Pesticides.

Full free report available at:

Fluoride Vol. 36 No. 4 231-240 2003 - Research Report 231


Boguslaw Machalinski (a), Magdalena Baskiewicz-Masiuk (a), Bogna Sadowska (a), Anna Machalinska (b), Mariola Marchlewicz (b), Barbara Wiszniewska (b), Iwona Stecewicz (a)

For Correspondence: Boguslaw Machalinski, MD, PhD., D.Sci.
(a) Department of General Pathology, Pomeranian Academy of Medicine (PAM), Al. Powstancow Wlkp. 72, 70-111 Szczecin, Poland. E-mail:
(b) Department of Histology and Embryology, PAM, Al. Powstancow Wlkp. 72, 70-111 Szczecin, Poland.

SUMMARY: Although potential toxic effects of sodium fluoride on early progenitor and stem cells have been reported previously, surprisingly few investigations have examined the effects of fluoride on human leukemic cells. To address this need, four different human leukemic cell lines (HL-60, HEL, TF-1, and K562) were exposed to increasing levels (0, 0.24, and 1.19 mM F) of two forms of fluoride: sodium fluoride (NaF) and sodium hexafluorosilicate (Na2SiF6). Because of its widespread use in water fluoridation, Na2SiF6 was investigated in addition to NaF. The early response effect of Na2SiF6 was greater, and in several cases significantly greater, than NaF on clonogenic growth and the induction of apoptosis in all four cell lines. These findings show that human leukemic cells can be influenced and damaged by fluorine compounds.

"Sodium fluosilicate (sodium silico fluoride) has been used to control ectoparasites on livestock, as well as crawling insects in homes and work buildings. It is approximately as toxic as sodium fluoride [highly toxic to all plant and animal life]. All uses in the U.S. have been cancelled."
-- Note from FAN: Unfortunately, this is not correct. Sodium fluosilicate is permitted to be used in pesticides as a List 3 Inert.
Ref: Recognition and Management of Pesticide Poisonings, 5th Edition, Chapter 8.
The Office of Pesticide Programs, US EPA

The major use of sodium hexafluorosilicate [sodium fluosilicate] and fluorosilicic acid is as fluoridation agents for drinking water. Sodium hexafluorosilicate has also been used for caries control as part of a silicophosphate cement, an acidic gel in combination with monocalcium phosphate monohydrate, and a two-solution fluoride mouth rinse. Both chemicals are also used as a chemical intermediate (raw material) for aluminum trifluoride, cryolite (Na3AlF6), silicon tetrafluoride, and other fluorosilicates and have found applications in commercial laundry. Other applications for sodium hexafluorosilicate include its use in enamels/enamel frits for china and porcelain, in opalescent glass, metallurgy (aluminum and beryllium), glue, ore flotation, leather and wood preservatives, and in insecticides and rodenticides. It has been used in the manufacture of pure silicon, as a gelling agent in the production of molded latex foam, and as a fluorinating agent in organic synthesis to convert organodichlorophosphorus compounds to the corresponding organodifluorophosphorus compound. In veterinary practice, external application of sodium hexafluorosilicate combats lice and mosquitoes on cattle, sheep, swine, and poultry, and oral administration combats roundworms and possibly whipworms in swine and prevents dental caries in rats. Apparently, all pesticidal products had their registrations cancelled or they were discontinued by the early 1990s... Exposure to sodium hexafluorosilicate is possible from its use to control crawling insects in homes and work buildings. The chemical has "high inherent toxicity," and children may ingest the material from crawling on the floors of treated houses (U.S. EPA, 1999).
Ref: Toxicological Summary for Sodium Hexafluorosilicate [CASRN 16893-85-9] and Fluorosilicic Acid [CASRN 16961-83-4]. Review of Toxicological Literature. October 2001. Prepared for Scott Masten, Ph.D. National Institute of Environmental Health Sciences.

Sodium hexafluorosilicate ([Na2SiF6] is also called:
Destruxol applex
Disodium hexafluorosilicate
Disodium silicofluoride
Ens-zem weevil bait
ENT 1,501
Fluorosilicate de sodium
Fluosilicate de sodium
Ortho earwig bait
Ortho weevil bait
Prodan (pesticide)
PSC Co-Op weevil bait
Silicate (2 - ), hexafluoro-, disodium (8CI, 9CI)
Silicon sodium fluoride
Sodium fluoride silicate
Sodium fluorosilicate
Sodium fluosilicate
Sodium silicofluoride
Sodium silicon fluoride
Super prodan UN2674 (DOT)

Related Chemicals:
Ref: Pesticide Action Network (PAN)
CAS No. Relation Chemical Name PAN & FAN data Some Notes from FAN:
16893-85-9 Parent * Sodium fluosilicate


US EPA List 3 inert

Registered in:
Australia, Canada, India, South Africa, Tanzania, Vietnam

UK: Cancelled

16919-19-0 Related (1)

Ammonium fluosilicate



US EPA List 3 inert

SYN: Ammonium silicofluoride

62449-69-8 Related (1) Ammonium fluosilicate on silica gel



SYN: Barium hexafluorosilicate
17125-80-3 Related (1)

Barium fluosilicate



Registered in: India

EU: Not allowed to be used as an active ingredient after July 25, 2003

SYN: Barium hexafluorosilicate

12062-24-7 Related (1)

Cupric fluosilicate



Copper silicofluoride,
Cupric hexafluorosilicate
1327-43-1 Related (1) Magnesium aluminum fluosilicate



US EPA List 3 inert  
16949-65-8 Related (1) Magnesium fluosilicate



53404-77-6 Related (1) Sodium aluminum fluosilicate



16871-71-9 Related (1)

Zinc fluosilicate



PAN Bad Actor Chemical:
Developmental or Reproductive Toxin

SYN: Zinc silicofluoride

Explanation from PAN:
* Parent: Compounds labeled with a "P" are the parent compound of the group. The parent chemical was chosen on the basis of available toxicity information, where chemicals with the maximum amount of toxicity information assigned to parent status. Where no toxicity information was available for any member of a group, we assigned parent status to the least derivatized member of the group for organic compounds (e.g., benzoic acid would be the parent instead of methyl benzoate), the sodium salt (for compounds with a common anion), or the chloride salt (for compounds with a common cation). These are general guidelines and not hard and fast rules, because the groups are rarely so easy to categorize. For some groups with no obvious parent, assignment of parent status was arbitrary.

Group 1: Salts, esters and/or complexes of the parent chemical, e.g., glyphosate and glyphosate, isopropylamine salt; 2,4-D and 2,4-D, butoxyethyl ester. Alternatively, the parent compound itself is an ester or salt, and related compounds are other esters or salts.

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