The European Chemicals Agency (ECHA) opened a public consultation on September 21, 2026, on Germany's proposals for harmonized classification and labeling (CLH) of nine organic anhydrides. Comments are open until November 20, 2026.
All nine proposals include classification as a respiratory sensitizer (Resp. Sens. 1, H334), and five also add skin sensitization (Skin Sens. 1, H317), according to ECHA's consultation listing. The consultation does not change any classification by itself, so current labels and safety data sheets (SDSs) stay as they are for now.
What Is Under Consultation
The consultation covers nine substances, all with Germany as dossier submitter. ECHA's listing gives these proposed entries:
| Substance | CAS number | Proposed entry |
|---|---|---|
| 1,2,3,6-tetrahydromethyl-3,6-methanophthalic anhydride, including isomers and combinations | 25134-21-8, 828-66-0, 53584-57-9 and others | Acute Tox. 3 (H331), Acute Tox. 4 (H302), Skin Irrit. 2 (H315), Eye Dam. 1 (H318), Resp. Sens. 1 (H334), Skin Sens. 1 (H317) |
| Chlorendic anhydride | 115-27-5 | Carc. 2 (H351), STOT SE 3 (H335), Skin Irrit. 2 (H315), Eye Irrit. 2 (H319), Resp. Sens. 1 (H334), Skin Sens. 1 (H317) |
| 4,4'-biphthalic dianhydride | 2420-87-3 | Resp. Sens. 1 (H334) |
| 4,4'-oxydiphthalic anhydride | 1823-59-2 | Resp. Sens. 1 (H334), Aquatic Chronic 3 (H412) |
| 4-chloroformylphthalic anhydride | 1204-28-0 | Skin Corr. 1 (H314), Eye Dam. 1 (H318), STOT SE 3 (H335), Resp. Sens. 1 (H334), Skin Sens. 1 (H317) |
| 5,5'-sulfonyldi(2-benzofuran-1,3-dione) | 2540-99-0 | Resp. Sens. 1 (H334) |
| Benzophenone-3,3':4,4'-tetracarboxylic dianhydride | 2421-28-5 | Resp. Sens. 1 (H334), STOT SE 3 (H335), Eye Irrit. 2 (H319) |
| Ethylene bis[1,3-dihydro-1,3-dioxo-iso-benzofuran-5-carboxylate] | 1732-96-3 | Eye Dam. 1 (H318), Resp. Sens. 1 (H334), Skin Sens. 1 (H317) |
| Tetrabromophthalic anhydride | 632-79-1 | Resp. Sens. 1 (H334), Skin Sens. 1 (H317) |
Respiratory sensitization is proposed for all nine substances. Skin sensitization is open for comment on all nine, but only five of the proposals include it. The four without it are 4,4'-biphthalic dianhydride, 4,4'-oxydiphthalic anhydride, 5,5'-sulfonyldi(2-benzofuran-1,3-dione), and benzophenone-3,3':4,4'-tetracarboxylic dianhydride.
Chlorendic anhydride, 4,4'-oxydiphthalic anhydride, and benzophenone-3,3':4,4'-tetracarboxylic dianhydride already have harmonized entries, so the proposals amend them. They add Carc. 2, Resp. Sens. 1, and Skin Sens. 1 for chlorendic anhydride and Resp. Sens. 1 for the other two. The remaining six would get harmonized entries for the first time.
Beyond sensitization, ECHA has opened other classes for comment on some substances: acute toxicity, skin corrosion or irritation, and serious eye damage or irritation for four of them (the first entry, 4-chloroformylphthalic anhydride, the ethylene bis-carboxylate, and tetrabromophthalic anhydride), carcinogenicity for chlorendic anhydride, and germ cell mutagenicity and specific target organ toxicity after single exposure for 4-chloroformylphthalic anhydride. For the first substance, the proposal also sets acute toxicity estimates of 0.5 mg/L (inhalation, dusts or mists) and 958 mg/kg body weight (oral).
Why Nothing Changes on Labels Yet
A CLH consultation is an early step, not a rule. Annex VI to the EU's CLP Regulation stays as it is for now, so the three existing entries keep applying. Suppliers continue to classify under today's duties: the harmonized entry where one exists, and their own assessment of the available data for everything else.
Once the consultation closes on November 20, ECHA's Committee for Risk Assessment (RAC) evaluates the proposals, takes the comments into account, and adopts an opinion. The European Commission then decides whether to make the classifications binding through a delegated act amending Annex VI. Annex VI amendments generally apply from a later date than their entry into force, which gives suppliers time to adapt before the new entries become mandatory. Each substance's progress can be followed in ECHA's registry of CLH intentions.
What Adoption Would Mean for SDSs and Supply Chains
Once adopted, the entries are binding for the hazard classes they cover, so suppliers would have to bring their SDSs, labels, and packaging into line. Under the proposals, hazard statement H334 (may cause allergy or asthma symptoms or breathing difficulties if inhaled) would apply to all nine substances and H317 (may cause an allergic skin reaction) to five of them, so Section 2 of the SDS (hazards identification) and the label elements would be the first places to change.
Mixtures that contain any of the nine substances may also need to be reassessed, since ingredient classifications feed into mixture classification.
The change can also reach beyond the label. Because sensitizers are a workplace exposure concern, employers may need to revisit their chemical risk assessments and protective measures for these substances.
How to Take Part Before November 20
Comments are submitted through ECHA's CLH consultation portal, which has a separate comment page for each substance. Under ECHA's general rules for these consultations, the standard period is 60 days and comments close at 23:59 Helsinki time on the last day. Comments must relate to hazard classes that are open for comment, and late submissions are left out of the response-to-comments table. ECHA also encourages comments that support a proposed classification, not only objections.
Companies can start by searching their product and supplier records for the nine substances. The first entry covers isomers and combinations under further CAS numbers, including 828-66-0 and 53584-57-9, so a search on 25134-21-8 alone would miss some of them. The open hazard classes differ between the nine substances, so a case made for one does not carry over to the others.
Teams that keep their SDSs in a searchable library can quickly find the products whose SDSs list one of the nine CAS numbers, then flag those SDSs for review as the proposals move through RAC and the Commission.
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Arysha Alif Khan
Arysha Alif Khan is an EHS and chemical safety specialist with a background in biochemistry, biotechnology, and public health. She works closely with the product and regulatory teams to turn complex chemical regulations, SDS requirements, and workplace safety standards into clear, practical guidance for people.