Reading Section 3 of an epichlorohydrin safety data sheet requires separating three distinct regulatory functions: the chemical identity disclosure, the concentration range that triggers mixture classification, and the embedded hazard category that carries through to Section 2. For 1-chloro-2,3-epoxypropane, CAS 106-89-8, EC 203-439-8, Annex VI index 603-026-00-6, the carcinogen declaration is not a standalone sentence; it is encoded as Carc. 1B, H350 under the CLP framework and as Carcinogen Category 1B under OSHA HazCom 2012. Section 3 of a single-substance SDS may list epichlorohydrin at ≥99.0% by weight, with the remaining balance divided among water and producer-specific chlorinated impurities. The absence of additional named constituents in Section 3 does not mean the product is free of all trace species; it means no other classified constituent is present above the relevant cut-off. For a downstream reader, the key operational question is whether ECH is present as the bulk substance or as a lower-concentration component in a formulated mixture, because the carcinogen disclosure threshold changes the obligations for labelling and stock reporting.

The ECH entry that activates Carc. 1B mixture classification at 0.1% in CLP and OSHA formats

Under Regulation (EC) No 1272/2008, ECH is listed in Annex VI with index number 603-026-00-6. The harmonised entry includes Carc. 1B; H350, and the generic concentration limit for carcinogenicity category 1B is 0.1%. Because no specific concentration limit is assigned to ECH in Annex VI, a mixture containing epichlorohydrin at ≥0.1% by weight is classified as Carc. 1B unless a producer-specific bridging principle alters the evaluation. Under OSHA Hazard Communication Standard 29 CFR 1910.1200, the cut-off for carcinogen category 1B is likewise 0.1%. Therefore the SDS Section 3 listing for a formulated epoxy resin, textile auxiliary, or water-treatment intermediate must keep ECH visible if the loading reaches this threshold. The phrase “contains epichlorohydrin” does not independently constitute the carcinogen declaration; the declaration is complete only when the concentration and the GHS category are read together.

From a production-scale perspective, the 0.1% boundary is not a theoretical value. In epoxy resin plants, batch tickets for reactive diluent packages may contain ECH residues at 0.05% to 0.2% depending on reactor stripping efficiency. When the loading crosses 0.1%, the downstream SDS generator must change the Section 2 hazard statement to H350 and update Section 3 to disclose epichlorohydrin explicitly. This is not a change in the bulk material itself; it is a classification state change driven by the same analytical result reported on the certificate of analysis. Batch-to-batch variance around the cut-off therefore creates a compliance risk if the SDS is not tied to an actual assay rather than a nominal recipe.

Are ECH impurities in high-purity resin-grade material declared separately within Section 3?

For a single-substance SDS prepared under REACH Annex II as amended by Commission Regulation (EU) 2020/878, Section 3.1 must include the main substance, its CAS and EC numbers, and any impurities or stabilising additives that are themselves classified and contribute to the classification. For commercial epichlorohydrin, producer data commonly list water in the range of 0.01% to 0.05% and total chlorinated by-products below 0.1%, although these figures are process-specific and may change with distillation conditions. Since water is not classified and the chlorinated impurities are frequently below the relevant concentration cut-off, they are not separately named in Section 3. The phrase “impurities do not contribute to classification” may appear instead. This is a regulatory declaration rather than a purity certificate; a resin batch record still requires gas chromatographic area percent for total unknown peaks, because Section 3 is not a specification sheet.

In resin manufacturing, a producer’s online gas chromatograph may show epichlorohydrin at 99.4% while the adjacent SDS Section 3 still records ≥99.0%. This spread does not create a Section 3 error; the SDS concentration is a conservative band, not a release limit for the plant. However, in processes where stoichiometric dosing to bisphenol A is controlled to a molar ratio of 1.05:1 to 1.15:1, the difference between 99.0% and 99.7% assay changes the available reactive epoxide equivalent by roughly 0.7%, which must be corrected through metering pump setpoints or load-cell batch calculations.

When an SDS Shows ECH at 0.1% to 1% in a Downstream Formulation

In a mixture, Section 3.2 requires disclosure of ECH when its concentration exceeds the generic carcinogen cut-off of 0.1%. A trade secret expression such as 0.1–1% is not a vague band; it is the permissible concentration range under the relevant SDS format and it immediately triggers the mixture-level Carc. 1B classification. Readers should not infer that the upper bound is the actual concentration. A formulation at 0.3% ECH by weight and a formulation at 0.9% may both appear in the same 0.1–1% band, but the latter contains three times the ECH mass per unit volume. For occupational hygiene estimates, the band can be converted to a mass fraction: 0.1% equals 1,000 ppm by mass in the liquid, 1% equals 10,000 ppm by mass. These are not vapour concentrations in ppm by volume.

The distinction matters for exposure declarations. Section 3 does not state an 8-hour TWA. It provides the mass fraction needed to estimate the maximum releasable ECH inventory in a room or process area. For a two-component epoxy system containing ECH as a residual monomer in the resin portion, the Section 3 disclosure of 0.1–1% tells the industrial hygienist that each kilogram of that resin carries between 1 g and 10 g of ECH. The inhalable airborne concentration that results from this inventory depends on material temperature, surface area, ventilation airflow, and the vapour pressure of ECH. A reader who treats the 0.1% cut-off as a direct airborne limit misreads the document. The actual airborne limit appears in Section 8, not Section 3.

For ECH, exposed workers are protected by a hierarchy of occupational exposure limits that cross-reference the ingredient disclosure in Section 3. Under 29 CFR 1910.1000, the OSHA permissible exposure limit is 5 ppm (19 mg/m³) as an 8-hour time-weighted average with a skin notation. The NIOSH recommended exposure limit is 0.5 ppm (1.9 mg/m³) as a 10-hour TWA with a skin notation. ACGIH has assigned a threshold limit value of 0.5 ppm (1.9 mg/m³) with a skin notation and an A3 classification. Because these values are numerically smaller than the mass-fraction value implied by the 0.1% mixture threshold, Section 3 concentration alone cannot determine compliance. The Section 3 value is the source term; the Section 8 value is the receptor limit. An ECH-containing resin formulated at 0.5% is above the GHS carcinogen classification threshold and must carry H350, but the airborne concentration next to an open vessel may still be below the OSHA PEL if ventilation is high.

Section 3 does not create the airborne limit, but it establishes the reporting line for ECH exposure calculations.

The reporting line is most visible in an epoxy resin plant where the liquid resin is discharged at elevated temperature into vacuum pumps or collection tanks. If the Section 3 concentration is 0.2%, the corresponding ECH mass per tonne is 2 kg. An industrial hygienist can use that mass, together with the resin temperature and local exhaust velocity, to model the worst-case vapour emission. In this calculation, the Section 3 band is not a safety limit; it is the starting inventory. If the SDS instead uses a broad range of 0.1–1%, the source-term uncertainty expands from 1 kg to 10 kg per tonne. It is therefore a compliance weakness to write overly broad bands for a carcinogenic residue without supporting batch analytical data. Under REACH, a downstream formulator is expected to use the supplier’s concentration range to prepare its own SDS, but it may also request a specific exact concentration from the supplier for internal exposure scenarios. This exchange is not a request for toxicology advice; it is a supply-chain data flow under Article 31 of REACH.