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Annex II Entry 1177 CMR15/10/2010

Trioxymethylene (1,3,5-Trioxan)

Trioxymethylene (1,3,5-Trioxan) is listed in Annex II as a prohibited substance for cosmetic products placed on the EU market.

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Prohibited substance— Annex II, EU Regulation 1223/2009
Entry: 1177
CMR

Chemical identity and properties

PubChem 2D chemical structure for CAS 110-88-3
CAS 110-88-3PubChem CID 8081

1,3,5-Trioxane

1,3,5-trioxane is a saturated organic heteromonocyclic parent that is cyclohexane in which the carbon atoms at positions 1, 3 and 5 are replaced by oxygen atoms. It is a saturated organic heteromonocyclic parent and a trioxane. — ChEBI

IUPAC name
1,3,5-trioxane
Molecular formula
C3H6O3
Molecular weight
90.08 g/mol
Exact mass
90.031694049 Da
XLogP3
-0.4
Topological polar surface area
27.7 Ų
Hydrogen-bond donors
0
Hydrogen-bond acceptors
3
Covalent units
1
Defined stereocentres
0

Also known as

s-TrioxaneTrioxymethyleneTrioxaneMetaformaldehydeTriformolFormaldehyde, trimerTrioxansym-Trioxane
16 more reported names
1,3,5-TrioxacyclohexaneAldeformMarvosans-TrixaneTriossimetileneTrioxymethyleenTrioxymethylenTrioxin1,3,5-Trioxan46BNU65YNYNSC-26347CHEBI:38043RefChem:412664CHEBI:38044203-812-5NSC 26347
Open full PubChem recordPubChem annotations3D structure image
External database identifiers

Evidence from additional scientific databases

NIH PubChem PUG-View
Exact identifier match8081

Attributed physical-property, hazard, environmental and use annotations.

  • Solubility: greater than or equal to 100 mg/mL at 68 °F (NTP, 1992) Source: CAMEO Chemicals
  • Solubility: SOL IN WATER: 17.2 G/100 ML @ 18 °C, 21.2 @ 25 °C; EASILY SOL IN ALC, KETONES, ETHER, ACETONE, ORG SOLVENTS, CHLORINATED & AROMATIC HYDROCARBONS; SLIGHTLY SOL IN PENTANE, PETROLEUM ETHER, LOWER PARAFFINS Source: Hazardous Substances Data Bank (HSDB)
  • Solubility: SOL IN BENZENE, CARBON TETRACHLORIDE, CHLOROFORM, CARBON DISULFIDE Source: Hazardous Substances Data Bank (HSDB)
  • First Aid: EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.; SKIN: IMMEDIATELY flood affected skin with water while removing and isolating all contaminated clothing. Gently wash all affected skin areas thoroughly with soap and water. If symptoms such as redness or irritation develop, IMMEDIATELY call a physician and be prepared to transport the victim to a hospital for treatment.; INHALATION: IMMEDIATELY leave the contaminated area; take deep breaths of fresh air. If symptoms (such as wheezing, coughing, shortness of breath, or burning in the mouth, throat, or chest) develop, call a physician and be prepared to transport the victim to a hospital. Provide proper respiratory protection to rescuers entering an unknown atmosphere. Whenever possible, Self-Contained Breathing Apparatus (SCBA) shou Source: CAMEO Chemicals
  • Signal: Danger Source: Regulation (EC) No 1272/2008 of the European Parliament and of the Council
  • GHS Hazard Statements: H228: Flammable solid [Danger Flammable solids]; H335: May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation]; H361d ***: Suspected of damaging the unborn child [Warning Reproductive toxicity] Source: Regulation (EC) No 1272/2008 of the European Parliament and of the Council
  • Precautionary Statement Codes: P203, P210, P240, P241, P261, P271, P280, P304+P340, P318, P319, P370+P378, P403+P233, P405, and P501 (click each P-code to see the statement) Source: Regulation (EC) No 1272/2008 of the European Parliament and of the Council
  • Signal: Danger Source: European Chemicals Agency (ECHA)
  • GHS Hazard Statements: H228 (100%): Flammable solid [Danger Flammable solids]; H335 (100%): May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation]; H361 (99.3%): Suspected of damaging fertility or the unborn child [Warning Reproductive toxicity] Source: European Chemicals Agency (ECHA)
  • Precautionary Statement Codes: P203, P210, P240, P241, P261, P271, P280, P304+P340, P318, P319, P370+P378, P403+P233, P405, and P501 (click each P-code to see the statement) Source: European Chemicals Agency (ECHA)
  • ECHA C&L Notifications Summary: Aggregated GHS information provided per 285 reports by companies from 14 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.; Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website. Source: European Chemicals Agency (ECHA)
  • Signal: Danger Source: NITE-CMC
  • GHS Hazard Statements: H228: Flammable solid [Danger Flammable solids]; H370: Causes damage to organs [Danger Specific target organ toxicity, single exposure]; H372: Causes damage to organs through prolonged or repeated exposure [Danger Specific target organ toxicity, repeated exposure] Source: NITE-CMC
  • Precautionary Statement Codes: P210, P240, P241, P260, P264, P270, P280, P308+P316, P319, P321, P370+P378, P405, and P501 (click each P-code to see the statement) Source: NITE-CMC
  • GHS Hazard Statements: H336: May cause drowsiness or dizziness [Warning Specific target organ toxicity, single exposure; Narcotic effects]; H360: May damage fertility or the unborn child [Danger Reproductive toxicity]; H373: May causes damage to organs through prolonged or repeated exposure [Warning Specific target organ toxicity, repeated exposure] Source: NITE-CMC
  • Precautionary Statement Codes: P203, P260, P261, P271, P280, P304+P340, P318, P319, P403+P233, P405, and P501 (click each P-code to see the statement) Source: NITE-CMC
  • NFPA Health Rating: 2 - Materials that, under emergency conditions, can cause temporary incapacitation or residual injury. Source: Hazardous Substances Data Bank (HSDB)
  • NFPA Fire Rating: 2 - Materials that must be moderately heated or exposed to relatively high ambient temperatures before ignition can occur. Materials would not under normal conditions form hazardous atmospheres with air, but under high ambient temperatures or under moderate heating could release vapor in sufficient quantities to produce hazardous atmospheres with air. Source: Hazardous Substances Data Bank (HSDB)
  • NFPA Instability Rating: 0 - Materials that in themselves are normally stable, even under fire conditions. Source: Hazardous Substances Data Bank (HSDB)

Mapped by: Existing checksum-valid CAS to unique PubChem CID match. Retrieved: 2026-08-31. Open source record

Scientific classifications and hazard annotations provide context and do not replace the market-specific regulatory decision shown above.

Additional source coverage and match status
SourceResultChecked
NIH PubChem PUG-ViewExact match2026-08-31

A recorded no-match is useful evidence that the source was checked; it is not a claim that the substance does not exist elsewhere.

Retrieved from NIH PubChem on 2026-09-02 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Record details

Chemical name

Trioxymethylene (1,3,5-Trioxan)

Regulatory information

Regulation

(EC) 2009/1223

See every entry this act set

SCCS opinions

CMR

CategoryCarcinogenicMutagenicReprotoxic
Cat. 2——✓

Key data

CAS
110-88-3
EC
203-812-5
Annex
II
Entry number
1177

Direct matches are limited for this record, so nearby entries from Annex II are shown as well.

Annex II 1178
Nearby record in the same annex

Propargite (ISO)

CAS: 2312-35-8
EC: 219-006-1
Annex II 1175
Nearby record in the same annex

Phenol

CAS: 108-95-2
EC: 203-632-7
Annex II 1180
Nearby record in the same annex

Molinate (ISO)

CAS: 2212-67-1
EC: 218-661-0

What Annex II means for Trioxymethylene (1,3,5-Trioxan)

Trioxymethylene (1,3,5-Trioxan) is listed as a prohibited substance under Annex II of EU Cosmetics Regulation 1223/2009 and must not be intentionally added. Article 17 separately addresses unintended small quantities that are technically unavoidable under good manufacturing practice and compatible with the Article 3 safety requirement.

Formulators must screen their ingredients and raw materials to ensure none contain this substance. Suppliers should provide documentation confirming absence when requested.

The page also surfaces 12 related annex records with overlapping identifiers, annex logic or naming patterns.

Compliance checklist

  • Verify this substance is absent from all raw materials and finished formulations.
  • Request absence confirmation or CoA from raw material suppliers.
  • Document the screening result in the Product Information File (PIF).
  • This substance has CMR classification. Review the CMR table above and verify current Annex II/III status before use.

Frequently asked questions

Yes. Trioxymethylene (1,3,5-Trioxan) is listed in Annex II of EU Cosmetics Regulation 1223/2009 and is prohibited as an intentionally added cosmetic ingredient. Article 17 provides a narrow exception for unintended small quantities that are technically unavoidable under good manufacturing practice, provided the product remains safe under Article 3.

CAS 110-88-3 is the unique numerical identifier assigned to Trioxymethylene (1,3,5-Trioxan) by the Chemical Abstracts Service. In cosmetic compliance work, the CAS number is used to cross-reference the substance across regulatory databases, raw material specifications and safety assessment reports. Multiple EU annex entries may share the same CAS number if the same substance appears under different conditions or in different annexes.

Trioxymethylene (1,3,5-Trioxan) has a CMR (carcinogenic, mutagenic or reprotoxic) classification under EU CLP Regulation. Under Article 15 of EU Cosmetics Regulation 1223/2009, CMR substances of category 1A or 1B are prohibited in cosmetics unless specifically permitted. Category 2 CMR substances may be used only if assessed safe by the SCCS. Always verify current annex status and any applicable derogations before use.

Use the INCI Checker tool on this site to paste your full ingredient list (INCI) and scan it against all Annex II–VI entries. The tool highlights any ingredients that match restricted, prohibited or allergen-flagged records. This is useful for rapid compliance screening of finished product formulas or raw material declarations.
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Source note for Annex II record Trioxymethylene (1,3,5-Trioxan)

This page summarizes one Annex II record for Trioxymethylene (1,3,5-Trioxan) from public European Commission cosmetic materials and adds linked inventory or identifier matches when available.

Use this record page to review Annex II conditions for Trioxymethylene (1,3,5-Trioxan), but confirm any final regulatory decision against the current official annex wording and source files.

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