Section 3 Composition and Information on Ingredients
In a Safety Data Sheet (SDS), Section 3 provides vital information on the chemical identity, concentration, and classification of any hazardous ingredients present in a substance or mixture.
This is a key part of hazard communication mandated by the Globally Harmonized System (GHS) and adopted in most jurisdictions via local legislation (e.g., EU CLP Regulation, REACH Annex II). Section 3 enables downstream users, emergency responders, and regulatory authorities to:
- Identify the chemical nature of the product (substance or mixture)
- Recognize hazardous components that contribute to the product classification
- Assess potential health and environmental hazards
- Determine control measures and exposure assessments
1. Substance or Mixture Identification
The first step is to determine whether the product is classified as a substance or mixture:
- Substance: A single chemical element or compound, with any impurities that do not substantially change its classification
- Mixture: A formulated blend of two or more substances
2. Listing Hazardous Ingredients
Under GHS and regional regulations, suppliers must list each ingredient that:
- Is classified as hazardous, and present above certain concentration thresholds (≥ 1% for most hazards, ≥ 0.1% for carcinogens)
- Has official concentration limits or specific concentration limits (SCLs)
- Is a Substance of Very High Concern (SVHC) under REACH (≥ 0.1%)
- Has a Union Workplace Exposure Limit (WEL) or national OEL
3. Hazard Classification and Labeling Elements
Alongside the ingredient identity, Section 3 must include:
- GHS classification (e.g., Flam Liq 3, H226)
- Supplemental hazard information (EUH statements where applicable)
- M-Factors for substances highly toxic to aquatic environment
- Acute Toxicity Estimates (ATEs) for acute toxicity
- Specific Concentration Limits (SCLs) where applicable
4. Confidential Business Information (CBI)
Regulations allow limited withholding of certain ingredient identities to protect trade secrets, but only when justified and in compliance with local requirements. Even if exact ingredient identities and concentrations are masked, hazard classification details must still be shared to ensure safe use.
3.1. Substance
Chemical Name
Systematic names are complicated and as such are often abbreviated or substituted by a common name. Where the substance is listed in Part 4 of CLP, then the proper chemical name which appears in the regulations will be used.
3.2. Mixture
In subsection 3.2 the supplier will provide a list of the hazardous substances which make up the mixture. If the mixture - and none of its ingredients - are classified as hazardous substances, then the supplier is not required to provide the ingredients.
REACH Registration Number
Any ingredient registered under REACH will have been assigned a REACH registration number. Distributors may omit the last four digits to avoid sharing supplier identity.
Practical Tips for Compliance
- Confirm classification data: Use harmonized classification lists or up-to-date substance dossiers
- Use clear concentration notation: Specify exact percentages or allowed ranges
- Check SCL and M-factor references: Identify published values from official sources
- Respect confidentiality claims: Use generic identifiers as permitted by regulations
Important Requirements
- At least one identification number is legally required for substances
- The concentration (range) of hazardous ingredients must be given as weight for weight percentage
- Upper limits of concentration ranges should be used to avoid underestimating hazards
- M-Factors should be provided for environmentally hazardous substances (strongly recommended)
Conclusion
Section 3 of an SDS is critical for cornerstone compliance with GHS, REACH Annex II, and CLP, allowing users to understand the hazards posed by each component of a product. A compliant Section 3 must list all relevant identifiers, concentration or concentration ranges, and classification details for hazardous ingredients. This empowers downstream users to protect worker health, ensure environmental safety, and maintain regulatory conformity.