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Annex II Entry 1394 CMR30/07/2020

Diboron trioxide; boric oxide

Diboron trioxide; boric oxide 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: 1394
CMR

Chemical identity and properties

PubChem 2D chemical structure for CAS 1303-86-2
CAS 1303-86-2PubChem CID 11073337

Boron oxide (B2O3)

Boron oxide appears as colorless, semi-transparent glassy lumps or hard white odorless crystals. Mp 450 °C; bp: 1860 °C. Density: 2.46 g cm-3. Moderately soluble in water. Used as an insecticide; as the starting material for the synthesis of other boron compounds; as a fluxing agent in enamels and glasses; and in mixture with 2-6% boron nitride, as a bonding agent in the hot isostatic pressing of boron nitride ceramics. — CAMEO Chemicals

IUPAC name
2,4,5-trioxa-1,3-diborabicyclo[1.1.1]pentane
Molecular formula
B2O3
Molecular weight
69.63 g/mol
Exact mass
70.0033542 Da
Topological polar surface area
27.7 Ų
Hydrogen-bond donors
0
Hydrogen-bond acceptors
3
Covalent units
1
Defined stereocentres
0

Also known as

Boron sesquioxide483W67CPF4Boron OxydatumFused boric acidCaswell No. 109BBoric oxide (B2O3)RefChem:917472Boric acid (HBO2), anhydride
16 more reported names
CHEBI:35777215-125-8259-231-2620-845-4B2O3Boric anhydrideBoric oxideBoron oxideCHEBI:30163Diboron trioxideBORON OXIDE [MI]Boron oxide (99.6%-B)Boron oxide (99.9%-B)Boron oxide, (H2O 200ppm)Boron Oxide Powder, 98% NanoBoron oxide, Puratronic, (H2O 200ppm)
Open full PubChem recordPubChem annotations3D structure image

Evidence from additional scientific databases

NIH PubChem PUG-View
Exact identifier match11073337

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

  • First Aid: Excerpt from NIOSH Pocket Guide for Boron oxide:; Eye: IRRIGATE IMMEDIATELY - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately.; Skin: WATER FLUSH PROMPTLY - If this chemical contacts the skin, flush the contaminated skin with water promptly. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water promptly. If irritation persists after washing, get medical attention.; Breathing: FRESH AIR - If a person breathes large amounts of this chemical, move the exposed person to fresh air at once. Other measures are usually unnecessary.; Swallow: MEDICAL ATTENTION IMMEDIATELY - If this chemical has been swallowed, get medical attention immediately. (NIOSH, 2024) Source: CAMEO Chemicals
  • First Aid: (General first aid procedures); Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately.; Skin: Water flush promptly - If this chemical contacts the skin, flush the contaminated skin with water promptly. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water promptly. If irritation persists after washing, get medical attention.; Breathing: Fresh air; Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately. Source: The National Institute for Occupational Safety and Health (NIOSH)
  • Signal: Danger Source: Regulation (EC) No 1272/2008 of the European Parliament and of the Council
  • GHS Hazard Statements: H360FD: May damage fertility; May damage the unborn child [Danger Reproductive toxicity] Source: Regulation (EC) No 1272/2008 of the European Parliament and of the Council
  • Precautionary Statement Codes: P203, P280, P318, 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: H360 (95.1%): May damage fertility or the unborn child [Danger Reproductive toxicity]; H360FD (13.1%): May damage fertility; May damage the unborn child [Danger Reproductive toxicity] Source: European Chemicals Agency (ECHA)
  • Precautionary Statement Codes: P203, P280, P318, 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 588 reports by companies from 17 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: H319: Causes serious eye irritation [Warning Serious eye damage/eye irritation]; H335: May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation]; H360: May damage fertility or the unborn child [Danger Reproductive toxicity] Source: NITE-CMC
  • Precautionary Statement Codes: P203, P261, P264+P265, P271, P280, P304+P340, P305+P351+P338, P318, P319, P337+P317, P403+P233, P405, and P501 (click each P-code to see the statement) Source: NITE-CMC
  • Signal: Warning Source: NITE-CMC
  • GHS Hazard Statements: H303: May be harmful if swallowed [Warning Acute toxicity, oral]; H316: Causes mild skin irritation [Warning Skin corrosion/irritation]; H319: Causes serious eye irritation [Warning Serious eye damage/eye irritation]; H335: May cause respiratory irritation [Warning Specific target organ toxicity, single exposure; Respiratory tract irritation] Source: NITE-CMC
  • Industry Uses: Not Known or Reasonably Ascertainable; Catalyst; Flux agent; Flame retardant; Hardener; Other; Processing aids not otherwise specified Source: EPA Chemical Data Reporting (CDR)

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

Diboron trioxide; boric oxide

Chemical / IUPAC name

Diboron trioxide; boric oxide

Regulatory information

Regulation

(EU) 2019/831

See every entry this act set

CMR

CategoryCarcinogenicMutagenicReprotoxic
Cat. 1B——✓

Key data

CAS
1303-86-2
EC
215-125-8
Annex
II
Entry number
1394

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

Annex II 1396
Nearby record in the same annex

Borates, tetraborates, octaborates and boric acid salts and esters, including: Disodium octaborate …

CAS: 12008-41-2 [1]/ 12280-03-4 [2]/ 10377-81-8 [3]/ 68003-13-4 [4]/ 12712-38-8 [5]/ -[6]/ 1332-07-6 [7]/ 1330-43-4 [8]/ 12267-73-1 [9]/ 13840-56-7 [10]/ 1303-96-4 [11]/ 12179-04-3 [12]
EC: 234-541-0 [1]/ 234-541-0 [2]/ 233-829-3 [3]/ 268-109-8 [4]/ 603-184-6 [5]/ -[6]/ 215-566-6 [7]/ 215-540-4 [8]/ 235-541-3 [9]/ 237-560-2 [10]/ 215-540-4 [11]/ 215-540-4 [12]

What Annex II means for Diboron trioxide; boric oxide

Diboron trioxide; boric oxide 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. Diboron trioxide; boric oxide 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 1303-86-2 is the unique numerical identifier assigned to Diboron trioxide; boric oxide 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.

Diboron trioxide; boric oxide 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 Diboron trioxide; boric oxide

This page summarizes one Annex II record for Diboron trioxide; boric oxide 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 Diboron trioxide; boric oxide, but confirm any final regulatory decision against the current official annex wording and source files.

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